A Modern Commentary on W.F. Denning’s, “Telescopic Work for Starlight Evenings (1891).

The monumental work of William F. Denning; "Telescopic Work for Starlight Evenings."

A good quality  modern reprint of William F. Denning’s; “Telescopic Work for Starlight Evenings.”

 

 

 

 

 

 

 

 

 

 

A Work Dedicated to David Gray.

Humility is the fear of the Lord; its wages are riches and honour and life.

Proverbs: 22:4

William Frederick Denning (1848-1931) is not a name that trips off the lips of the modern amateur astronomer. Of all the sky watchers of that era, it is arguably the literary work of The Reverend Thomas William Webb and especially his, Celestial Objects for Common Telescopes, that is most celebrated by amateur astronomers today. But while a great work in its own right, Webb was by no means the only populariser of astronomy in England, nor was he necessarily the most knowledgeable and dedicated to his hobby. That accolade, in this author’s opinion, should be reserved for an obscure Bristolian, who emerged from relative obscurity, in what was the meritocracy of the Victorian astronomical tradition, to pen one of the loveliest treatise on the art of visual observation, both with and without a telescope.

William F. Denning (1848-1931), the doyen of amateur astronomy.

William F. Denning (1848-1931), the doyen of amateur astronomy.

In this essay, we shall explore Denning’s masterful tome: Telescopic Work for Starlight Evenings, first published in 1891, to bring to the modern reader, a distillation of late nineteenth century astronomical knowledge; presented in such a way as to captivate the widest possible audience; both young and old, rich and poor, novice and learned alike. As explained in the preface to the work, the book was conceived at the behest of some of his closest friends, to gather together the best nuggets from his published writings in The Journal of the Liverpool Astronomical Society (of which he served as President in the years 1887-88), The English Mechanic, and The Observatory, among many others.

In Denning’s own words:

The methods explained are approximate, and technical points have been avoided with the view to engage the interest of beginners who may find it the stepping stone to more advanced works and to more precise methods. The object will be realised if observers derive any encouragement from its descriptions or value from its references, and the author sincerely hopes that not a few of his readers will experience the same degree of pleasure in observation as he has done for many years.

No matter how humble the observer, or how paltry the telescope, astronomy is capable of furnishing an endless store of delight to its adherents. Its influences are elevating and any of its features possess the charms of novelty as well as mystery. Whoever contemplates the heavens with the right spirit reaps both pleasure and profit and many amateurs find a welcome relaxation to the cares of business in the companionship of their telescopes on “starlight evenings”.

iv-v

Chapter I:The Telescope, Its Invention and the Development of its Powers

Covering pages 1 through 19.

In this chapter, Denning sets forth his extensive knowledge of the history of the telescope and its development over time. With an engaging writing style, he offers the reader an excellent summary of the key inventions that led to the state of affairs at the end of the 19th century.  Burning glasses, carved into a convex shape, were known to the ancients and were used as magnifying glasses. One such example, Denning informs us, was recovered from the excavations of the ancient Roman town of Pompeii, which met its terrible demise in 79 AD in the aftermath of the eruption of Mount Vesuvius. The Roman writer and philosopher, Pliny the Elder (23-79 AD) also gave mention to globules of glass, which could focus sunlight so intensely that it could ignite combustible material. The development of spectacle lenses from the 13th century onwards is also mentioned, but despite having some grasp of the optical science underlying their prescription, Denning is somewhat perplexed as to why it took so long for their adoption into telescopic devices. That said, he does proffer some tantalising historical titbits that the principle might have been known as early as the fourth decade of the sixteenth century :

Francastor (most probably a one Girolamo Fracastoro) , in a work published at Venice in 1538 states:-

“If we look though two eye lenses, placed the one upon the other, everything will appear larger and nearer.”

pp 4

Denning wryly comments that despite attempts by some fame hungry individuals to claim the invention of the telescope as their own – in particular Galileo Galilei and Simon Marius  – or who pronounced they had ‘figured the principle out’ from basic axiom of physics, it was very likely the case that one of mankind’s most revolutionary devices was very probably elucidated through purely accidental means! Indeed, Denning entertains the notion that the children of the Middleburg spectacle maker, Zachariah Jansen, might have stumbled upon the telescope by placing two spectacle lenses along the line of sight of their eyes, and unwittingly hit on an ingenious way of seeing faraway objects as though they were much closer.

Having said this, Denning appears to align himself with the opinions of many contemporary scholars in  attributing the invention of the telescope to a certain Hans Lippersheim (also known as Hans Lapprey), who was in possession of a simple telescope in 1608. On page 5-6 he refers to a critical piece of research carried out by the professional astronomer, Dr. Doberck, who showed the Lippersheim had applied for a thirty year patent from the Dutch States, in exchange for an annual stipend:

“He solicited the States, as early as the 2nd of October 1608, for a patent for thirty years, or an annual pension for life, for the instrument he had invented, promising then only to construct such instruments for the Government. After inviting the inventor to improve the instrument and alter it so that they could look through it with both eyes at the same time, the States determined on the 4th October, that from every province one deputy should be elected to try the apparatus and make terms with him concerning the price. The committee declared on the 6th October that the invention useful for the country, and they offered the inventor 900 florins for the instrument. He had at first asked 3000 florins for three instruments of rock crystal. He was then ordered to deliver the instrument within a certain time, and the patent was promised him on the condition that he kept the invention secret. Lapprey delivered the instrument in due time. He had arranged it for both eyes, and it was found satisfactory; but they forced him, against the agreement, to deliver two other telescopes for the same money, and refused the patent because it was evident that already several others had learned about the invention.”

pp 5-6

Denning proceeds form here to give an excellent overview of the unwieldy non-achromatic telescopes devised by Huygens, Hevelius, Cassini and Campani, amongst others, who ground and mounted lenses up to 8 inches in diameter with enormous focal lengths (up to 212 feet in focal length) yet all still delivering powers of 150 diameters or less. From here, Denning discusses the development of the much more convenient reflecting telescopes – the Gregorian, Cassegrain, Newtonian and other compound designs – and the problems associated with the construction of metallic mirrors fashioned from speculum metal (an alloy of copper, tin and small amounts of arsenic and/or antimony), which tarnished quickly and were exceedingly heavy in large apertures.

The author also discusses the origin of the Herschelian reflector, which involved tilting the primary mirror so that it reached a focus at the side of the tube without the requirement for a secondary flat mirror. The design, so Mr. Denning informs us, dates to 1728, when Le Maire first presented it to the French Academie des Sciences. Herschel adopted the design to increase the telescopes space penetrating power (light grasp) since it avoided a second reflection and hence saved more light that would otherwise have been lost with the addition of a second mirror. But such a design could not deliver the ‘defining power’ (image quality) of a conventional Newtonian. This is the principal reason why Herschel’s major work on the study of the planets and double stars were conducted with smaller Newtonian reflectors which were much more easy to operate and afforded the greatest degree of ‘mileage’ under the starry heaven.

Denning chronicles the growth in telescopic aperture throughout the 19th century, discussing such telescopes as the 6 foot aperture speculum built by the Third Earl of Ross as well as those used by Lassell and the great Melbourne telescope, which housed a 4-foot diameter (48 inch) speculum metal mirror with a focus of 28 feet. The latter telescope (produced by Howard Grubb of Dublin) was found to have poor defining power but Denning seems to lay the blame squarely with the shoddy mechanical set up of the instrument and not the optician.

The chapter ends with a discussion of the invention of the achromatic doublet by Chester Moor Hall (1729) and John Dollond and its development by Joseph von Fraunhofer, culminating with the creation of the sensational Dorpat Refractor of 9.5 inch aperture, and its state-of-the-art German equatorial mount, which ushered in the age of astrophysics.

Throughout the 19th century, astronomers began to build larger and larger refractors, first in Europe and then in North America, housed in magnificent domes that opened on every clear night to advance our knowledge of the heavens, and culminating with the Great Lick refractor of 36-inch aperture atop Mt. Wilson, California, which saw first light just three short years before the publication of Denning’s book. And while the author was aware that still larger refractors would surely come into existence, he seems more interested in a new technological advance in the production of parabolic mirrors for Newtonian telescopes; enter the silver-on-glass-reflector.

Beginning on page 14 and continuing on page 15, Denning describes the exciting work of the French physicist Jean Bernard Léon Foucault (1819-1868), who published a valuable memoir in which he described an ingenious new method of parabolising a glass disk followed by the deposition of a thin layer of silver upon its surface, and which exhibited much higher reflectivity than metal. It marked the end of the employment of speculum metal in telescope mirrors and ushered in a new age which promised to revolutionise both amateur and professional astronomy.

What is more, Denning informs us that Foucault developed lab-based methods of testing the accuracy of the parabolic surface in such a way as to render traditional testing methods – which involved time consuming and labour intensive trials under the stars – unnecessary. The customer could be assured of the quality of the mirror without it ever having being tested under the stars.

Denning writes:

Silver on glass mirrors immediately came into great request. The latter undoubtedly possess a great superiority over metal, especially as regards light gathering power, the relative capacity according to Sir John Herschel being as .824 to .436. Glass mirrors have also the advantage in being less heavy than those of metal. It is true that silver film is not very durable, but it can be renewed at any time with little trouble or expense.

pp 15.

Mr. Denning gives high praise to two British silver-on-glass mirror makers; George Henry With (1827-1904) of Hereford and George Calver (1834-1927) of Chelmsford, whose reflecting telescopes, ” were found nearly comparable to refractors of the same size.” pp 15.

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Author’s note: Modern scholarship seems to have converged on the name “Lippershey” as one of the earliest constructors of the telescope. Denning refers to the same man as “Lipperheim”. I was once reliably informed that the same chap should correctly be referred to as “Lipperhey”. After attempting to introduce this new nomenclature for a book I wrote, my editor returned it to “Lippershey” lol.

It is amusing that Denning referred to Galileo as “Galilei” to conform with the use of the surname in reference to individuals. Evidently, he thought it odd, which it most certainly is in retrospect.

Some memes are hard to shake.

Denning also points out that the great American refractors had recently employed powers of 3300 diameters in the resolution of the tightest double stars.

Denning was himself a convert to reflectors, after enjoying a fine 4.5 achromatic ( probably of f/15 relative aperture)  for a few years with which he carried out extensive solar work – a job ideally suited to the smaller refractor. In the end though, he sold that telescope in order to purchase a 10-inch With-Browning reflector in 1871 (when he was 23 years old) pictured on page 77 of the book. This telescope, so Denning will inform us, proved far more powerful than his former instrument. Indeed, Telescopic Work for Starlight Evenings is a distillation of twenty years of observations conducted with this same telescope.

The image below, kindly provided me by Denis Buczynski, a prominent member of the BAA, shows a 9.25 inch With-Browning (used by T.W. Webb) on a more sophisticated With-Berthon equatorial mount. But it serves our purposes well in illustrating the working dimensions of the telescope.

Denis Buczynski inspects the With/Berthon reflector ( BAA# 83) at his home in Lancaster.

Denis Buczynski inspects the With/Berthon reflector ( BAA# 83) at his home in Lancaster.

 

 

 

 

 

 

 

 

 

 

The image below pictures Denning beside his 10-inch.

William Denning ( 1848-1931) pictured with his With-Browning reflector on its simple altazimuth mount.

William Denning ( 1848-1931) pictured with his With-Browning reflector on its simple altazimuth mount.

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Chapter II: Relative Merits of Large and Small Telescopes

Covering pages 20 through 37.

Were it not for the vast sea of air that hugs our planet’s crust, the principles of telescopic astronomy would be clear and unequivocal; aperture rules, period. This is the reason for the spectacular success of the Hubble Space Telescope (HST), which, owing to its 2.4 metre primary mirror, has sent back the sharpest images of the heavens ever taken. It is also the reason why the widely anticipated replacement for HST, the James Webb Space Telescope, with its 6.4m segmented beryllium mirror, is expected to completely outclass it when it begins operations in 2018.

Down here on terra firma, the situation is rather more complicated. While there is no substitute for aperture if one wishes to pursue faint fuzzies, there is a great deal of anecdotal evidence that there exist practical limits on aperture in the pursuit of the finest lunar and planetary images. In a nutshell, although larger apertures offer the potential to see finer details, the atmosphere through which the amateur observes, often limits or even negates those advantages. Denning was arguably the first astronomer to raise awareness about this important topic and it was based upon his exceptional experience with instruments of all sizes, as well as his voluminous correspondences with the most active astronomers around the world.

Denning begins the chapter by discussing the rise in the number of large observatory- class instruments that had come to the fore during his lifetime and in past generations. Yet all the while he says:

There are some who doubt that such enormous instruments are really necessary, and question whether the results obtained with them are sufficient return for the great expense in their erection.

pp20

After discussing the realities of large telescopes, including their housing in an observatory, their mounting and maintenance, Denning extols the virtues of smaller instruments and alludes to a quality this author has previously referred to in the past as ‘mileage’:

…..small instruments involve little outlay, they are very portable, and require little space. They may be employed in or out of doors, according to the inclination and convenience of the observer. They are controlled with the greatest ease, and seldom get out of adjustment. They are less susceptible to atmospheric influences than larger instruments, and hence may be used more frequently with success and at places by no means favourably situated in this respect. Finally, their defining powers are of such excellent character as to compensate in a measure for feeble illumination.

pp 20-21

Denning begins with the telescopes of Sir William Herschel. Concerning his 4-foot reflector erected at Slough in 1789, he states that although Herschel discovered two of the inner satellites of Saturn shortly after the instrument was constructed, little else was achieved with it. Denning claims that Herschel much preferred the convenience of a smaller instrument – a 18.5 inch speculum of 20 foot focus in performing his famous sweeps for nebulae. Indeed the 4 foot telescope quickly fell into comparative disuse and his son, Sir John Herschel, had it sealed up for good on New Year’s Day, 1840. For defining power, Denning asserts that the great astronomer allegedly preferred instruments of much smaller size:

He found that his small specula of 7 foot focus and 6.3-in, aperture he had “light sufficient  to see the belts of Saturn completely well, and that here the maximum of distinctness might be much easier obtained than where large apertures are concerned.”

pp 21.

Following on from this, Denning discusses the Great 6-foot aperture telescope erected by the Third Earl of Rosse in Parsonstown (now Birr, Co. Offaly), Ireland. By 1891, this telescope had already been in service for 46 years and thus might provide insights into its relative utility. Denning concedes that it had done important work on elucidating the spiral morphology of many nebulae, M51 being perhaps the finest example. What follows is a fascinating overview of how it behaved. The satellites of Mars had eluded its grasp for three decades, until finally, in 1877, the outer moon, Deimos, was glimpsed twice, yet even then there was so much glare from the planet that no accurate measurements of its orbit were forthcoming. With Jupiter too, its enormous aperture was apparently of little advantage. This seems to be confirmed by a series of drawings made by William Parson’s son, Laurence (1840-1908), in the year 1873, and reproduced on page 128 in Thomas Hockey’s book, Galileo’s Planet: Observing Jupiter Before Photography. They reveal no more detail than could be obtained in a telescope ten times smaller.

Further insight into the efficacy of the Leviathan is gleaned from comments made by the Irish physicist, G.J. Stoney (1826-1911), who regularly used the instrument and who described his impression of γ2 Andromedae in a note made in 1878:

“The usual appearance [ of γ2 Andromedae ] with the best mirrors was a single bright mass of blue light some seconds in diameter and boiling violently.” On the best nights however, “the disturbance of the air would seem now and then suddenly to cease for perhaps half a second, and the star would then instantly become two very minute round specks of white light, with an interval between which, from recollection, I would estimate as equal to the diameter of either of them or perhaps slightly less. The instrument would have furnished this appearance uninterruptedly if the state of the air had permitted.

pp 23

Self evidently, it was not the optical quality of the mirror that was at issue but the environment in which it was placed. This was corroborated by a later observer in charge of the Leviathan, a one Dr. Boeddicker, active during the 1880s, who claimed that on a first class night, the amount of lunar detail seen with the giant mirror was “simply astounding.” We also learn that powers no higher than 600 diameters could be pressed into service, with occasional references to higher powers (1000x).

Denning then considers the work of William Lassell, who fashioned a number of large specula with which he discovered the two large satellites of Uranus; Umbriel and Ariel, independently co-discovered Hyperion, a faint satellite of Saturn and, just 17 days after the discovery of Neptune, its brightest moon, Triton (this name was not referred to by Denning as it was not formerly bestowed upon until a second Neptunian satellite, Nereid, was discovered in 1949).

Though Lassell, together with his assistant Mr. Marth, discovered a large number of nebulae from the sun drenched Mediterranean Island of Malta with his largest telescope of 4 foot aperture, Denning points out that it was with his 2 foot instrument that Mr. Lassell made all his planetary discoveries. Indeed, in 1871, Lassell wrote:

“There are formidable, and, I fear, insurmountable difficulties attending the construction of telescopes of large size…..These are primarily the errors and disturbances of the atmosphere and the flexure of the object-glasses or specula. The visible errors of the aperture are, I believe, generally in proportion to the aperture of the telescope…..Up to the size [referring to an 8in. O-G] in question, seasons of tranquil sky may be found where its errors are scarcely appreciable; but when go much beyond this limit (say to 2 feet and upwards),both these difficulties become truly formidable.”

pp 24.

That being said, Lassell also concluded that when conditions were fine, the advantages of aperture were clear for all to see. Concerning his largest telescopes he said:

“Nothwithstanding these disadvantages, they will, on some heavenly objects, reveal more than any small ones can.”

pp 24.

The chapter continues with Denning providing still more anecdotal evidence for the relative merits of large and small telescopes. Next in line, we hear about the 24.8 inch Cooke refractor erected by a well-to-do gentleman at Gateshead, England, which, despite its intimidating size, proved to have a ”singularly barren record”;

The owner of this fine and costly instrument wrote the author in 1885: “Atmosphere has an immense deal to do with definition. I have only had one fine night since 1870! I saw then what I have never seen since.”

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Author’s note: The Gateshead debacle is a particularly poignant story that has value for contemporary amateurs. Showmanship has no place in astronomy! The chap who installed the telescope obviously gave paltry attention to the environment in which the instrument was erected. The same gentleman seems to have had only a casual interest in astronomy, with little or no real experience of how such instruments would likely perform. The local seeing rendered the great telescope still born. One cannot help but wonder how many amateurs have done likewise over the years. Before spending lavish amounts of capital on a telescope, field testing the site on which it is to be constructed or used is mandatory. This accounts for the relative success of the large American refractors atop Mount Hamilton, for example, and the Great Meudon Refractor outside Paris, the sites of which were thoroughly field tested prior to their erection.

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The chapter continues with Denning relating other reports carried out by astronomers located at various observatories throughout the world. At the Paris Observatory, Dr. M. Wolf gained intimate acquaintance with various instruments including a 47.2 inch silver-on glass reflector, and a variety of smaller instruments, including a refractor of 15 inch aperture and 15.7 inch silver-on-glass reflector. Wolf wrote Denning concerning his visual experiences with these instruments:

“I have observed a great deal with the two instruments (both reflectors) of 15.7 and 47.2 inches. I have rarely found any advantage in using the larger one when the object was sufficiently luminous.” M. Wolf also avers that a refractor of 15 inches and a reflector of 15.7 inches will show everything  in the heavens  that can be discovered by instruments of very large aperture. He always found a telescope of 15.7-inch aperture surpass one of 7.9 inches, but expresses himself confidently that beyond about 15 inches increased aperture is no gain.

pp 26

Denning then relates the findings of Professor Young, who was assigned to a number of refractors, the largest being of 23 inch aperture, at Princeton, who related the following:

“The greater susceptibility of large instruments to atmospheric disturbances is most sadly true; and yet, on the whole, I find also true what Mr. Clark told me would be the case on first mounting our 23-inch instrument, that I can  almost always  see with the 23-inch everything I see with the 91/2 inch under the same atmospheric conditions, and see it better- if the seeing is bad, only a little better, if good immensely better.”

pp 27.

Another notable report comes from Mr. Keeler, who gained extensive experience with a number of instruments of various aperture atop Mount Hamilton:

Mr. Keeler adds: “According to my experience, there is a direct gain in power with increase in aperture. The 12-inch equatoreal brings to view objects entirely beyond the reach of the 61/2 inch telescope, and details almost beyond the perception with the 12-inch are visible at a glance with the 36-inch equatoreal.”

pp 28.

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Author’s note: These testimonies help to establish the veracity of a certain notion, that, from a visual perspective at least, greater aperture is only advantageous when atmospheric conditions cooperate. The relative efficacy of a given instrument is strongly dependent on the environment in which it is housed. Thus, no contradictions are found between theory and experiment.

I am mindful that this discussion focuses primarily on instruments generally larger than those found in amateur hands, but in recent years there has been an attempt by some amateurs (salesmen?), zealous to promote premium refractors over other models, to cultivate the erroneous view that the former can ” punch through the seeing” better on account of their “higher optical quality.” This arose from a deliberate twisting of some theoretical work conducted by this author in conjunction with theorist, Vladimir Sacek (which dealt mostly with the defocus aberration and its effects in long and short focal length systems). Although it was conceded that a slight advantage may be conferred on such higher quality instruments, in general, the seeing error completely overwhelms any small gains conferred in this way. As a further note of proof, many modern reflecting telescopes have Strehl ratios at or above those exhibited by ED refractors** (as measured by their polychromatic Strehl ratios) and so, by implication, ought to “punch through the seeing” even more effectively. That this is not commonly reported (either historically or in the ‘legitimate’ contemporary literature) demonstrates the effect is largely fictitious and irrelevant to any serious discussion of this interesting topic.

** The reader will note that, of the mirrors tested, it was the mass produced ones – read “least expensive” – that exhibited the highest Strehl. This is just one of many emerging test results found by inquisitive customers. This author can personally vouch for the quality of these mass produced mirrors, having regularly employed a 203mm and 130mm Newtonian(made by SkyWatcher) in field work.

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We shall not dwell further with the ideas conveyed by Mr. Denning in this engaging chapter, save to say that he concluded that there must exist some optimised aperture combining the best of both worlds for work on average nights:

There is undoubtedly a certain aperture which combines in itself sufficient light-gathering power with excellent definition. It takes a position midway between great illuminating power and sharp definition on the other. Such an aperture must form the best working instrument  in an average situation upon ordinary nights and ordinary objects. M. Wolf fixes this aperture at about 15 inches, and he is probably near the truth.

pp 35.

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Author’s note: This author is in agreement with Denning’s general conclusion. Indeed, this topic was explored in relation to the efficacy of resolving double stars, where a 8-inch aperture was found to be optimal in one interesting analysis.

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Chapter III: Notes on Telescopes and Their Accessories

Covering Pages 38 through 65.

In this chapter, the Last Master discusses the best choices of telescope and accessories needed by the amateur who wishes to pursue a serious, long-term study  of the firmament and begins with some sage advice:

The subject of the choice of telescope has exercised  every astronomer more or less, and the question as to the best form of instrument is one which has occasioned  endless controversy. The decision is an important one to amateurs, who at the outset of their observing careers require the most efficient instruments obtainable at reasonable cost. It is useless applying to scientific friends who, influenced by different tastes, will give an amount of contradictory advice that will be very perplexing. Some invariably recommend a small refractor and unjustly disparage reflectors, as not only unfitted for very delicate work, but as constantly needing re-adjustment and re-silvering.*

Others will advise a moderate-sized reflector as affording wonderfully fine views of the Moon and planets. The question of cost is greatly in favour of the latter construction, and, all things considered, it may claim an unquestionable advantage. A man who has decided to spend a small sum for the purpose not merely of gratifying his curiosity but of doing really serviceable work, must adopt the reflector, because refractors of, say, 5 inches and upwards are far too costly, and become enormously expensive as the diameter increases. This is not the case with reflectors; which come within the reach of all, and may indeed be constructed by the observer himself with a little patience and ingenuity.

*My 10-inch reflector by With-Browning was persistently used for four years without being resilvered  or once getting out of adjustment.

pp 38-39

Denning emphasises the convenience of reflectors over equivalent aperture refractors and mentions the innovations of the new silver-on-glass telescope makers, who managed to decrease the focal ratio, allowing decent aperture and viewing comfort to be maximised. George Calver had already begun to make telescopes with focal ratios as short as 5 or 6, which are now ubiquitous and deservedly popular. Denning estimates that a 8-inch reflector is equivalent to a 7-inch refractor (referring to a long focus instrument) in relative light gathering power, but in terms of defining power, especially in relation to planetary observing, Denning considers them equally good at equal aperture.

Having had the pleasure of observing through some of the finest telescopes in England, Denning was in a unique position to offer sensible advice to his readers:

An amateur who really wants a competent instrument, and has to consider cost, will do well to purchase a Newtonian reflector. A 41/2-inch refractor will cost about as much as a 10-inch reflector, but, as a working tool, the latter will possess a great advantage. A small refractor, if a good one, will do wonders, and is a very handy appliance, but it will not have sufficient grasp of light for it to be thoroughly serviceable on faint objects. Anyone hesitating in his choice should look at the cluster about χ Persei through instruments such as alluded to, and he will be astonished at the vast difference in favour of the reflector….. When high magnifications are employed on a refractor of small aperture, the images of planets become very faint and dusky, so that details are lost.

pp 41-42

Later he elaborates on the relative effectiveness of reflectors and refractors:

To grasp details there must be a fair amount of light. I have seen more with 252 on my 10-inch reflector than with 350 on a 51/4 inch refractor, because of the advantage of the brighter image in the former case.

pp 49

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Author’s note: How refreshingly honest and insightful Mr. Denning is! Having owned and enjoyed a number of smaller refractors of apochromatic and long-focus achromatic pedigree over the years (of 5- and 6-inch aperture), they have all paled in comparison to a 8-inch f/6 Newtonian on virtually all objects (the Sun being a memorable exception), and yet cost many times less. Vanity formed a large part in this author’s recalcitrance to embrace the genius of Newtonian optics, but when given a fair chance (proper acclimation and accurate alignment of the optical train), the refractors left little to be desired. For some, it remains an inconvenient truth that a well executed, mass market 20cm f/6 reflector would wipe the floor with the finest 5-inch glass on Earth, but it is undoubtedly true.

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Mr. Denning is however, sympathetic to the casual observer and acknowledges the role a small refractor might play in the pursuit of happy adventures:

Out of door observing is inconvenient in many respects, and those who procure a telescope merely to find a little recreation will soon acknowledge a small refractor to be eminently adapted to their purposes and conveniences.

pp42

That being said, Denning is careful to qualify this statement with the following:

Those who meditate going farther afield, and taking up observations habitually as a means of acquiring practical knowledge, and possibly of doing original work, will essentially need different means. They will require reflectors of about 8 or 10 inches aperture; and if mounted in the open on solid ground, so much the better, as there will be a more expansive view, and a freedom from heated currents, which renders an apartment unsuited to observations, unless with small apertures where the effects are scarcely appreciable. A reflector of the diameter mentioned will command sufficient light grasp to exhibit the more delicate features of planetary markings, and will show many other difficult objects in which the sky abounds. If the observer is especially interested in the surface configuration of Mars and Jupiter he will find a reflector a remarkably efficient instrument. On the Moon and planets it is admitted that its performance is, if not superior, equal to that of refractors.  If however, the inclination of the observer leads him in the direction of double stars, their discovery and measurement, he will perhaps find a refractor more to be depended upon, though there is no reason to why a well mounted reflector should not be successfully employed in this branch.

pp 42-43.

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Author’s note: Denning’s commentary here resonates very strongly with this author’s field experience. In respect of double stars, the 8-inch Newtonian was found to be a more effective instrument than a custom-made 5″ f/12 classical refractor, though historically, and inch for inch, there is overwhelming evidence to show that the classical refractor is better suited to resolving binary systems to the limits imposed by their aperture. Indeed, for this exacting task, they remain primus inter pares.

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Mr. Denning feels the images of stars in refractors are better than reflectors:

As far as my own experience goes, the refractor gives decidedly the best image of a star. In the reflector, a bright star under moderately high power is  seen with rays extending right across the field, and these appear to be caused by the supports of the flat.

pp 43.

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Author’s note: The stellar images in refractors are indeed very pretty, the Fraunhofer diffraction rings being very subdued and sometimes quite invisible on stars of lesser glory. Newtonians show diffraction spikes around bright stellar luminaries, and brilliant planets like Venus present with a singularly peculiar aspect in a moderately large Newtonian.

A Cruciform Venus

A Cruciform Venus, as seen with a 8-inch f/6 Newtonian on the evening of Saturday April 25 2015.

While this is certainly the case, it is a subjective point. Having accustomed myself to viewing through Newtonians, I must confess to finding these difrraction spikes to be rather beautiful. And while they may bother some individuals, they do not degrade the image in any significant way and can be ignored or unlearned.

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The chapter continues with a brief discussion on telescope testing. Denning’s approach is very down to Earth in this regard. He recommends that one should always try before you buy, especially if the instrument is second hand. As for the tests themselves, Denning does not recommend the Moon, as it is “too easy,” there being too much wonderful detail on view to side track the observer. Instead he recommends turning the telescope on bright planets, especially Jupiter and Venus to assess its defining power. Elaborating on Venus, he recommends  viewing at dusk or dawn, preferably when the planet has reached a decent altitude. As the magnification is cranked up, the disk of the planet should remain ” beautifully sharp and white.” A good telescope ought to hold its definition as the power is increased, with only an enfeebling of light as the image is spread over a larger area. A lesser telescope will show a deterioration of definition under the same conditions, producing a “mistiness” which confuses the definition in a palpable manner. Nor can these errors be ‘focused out’.

Denning also recommends star testing on a second or third magnitude star, the high power image of which ought to be tiny, circular and free from other distortions. If colour is seen in a reflector, it is probably the eyepiece and not the telescope that is at fault, though he does not mention the effects of atmospheric refraction that can manifest itself if the object under scrutiny is at a low altitude. He is also careful to distinguish between atmospheric distortion and a bona fide optical fault. Testing even a first rate telescope on a bad night of seeing is sure to produce iffy results and so these tests ought to be carried out over several nights to be certain of where the problem lies. Denning also  mentions the intra- and extra-focal colours of the diffraction rings seen in well corrected achromatic refractors.

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Author’s note: It is interesting that Denning does not suggest double stars as a test of telescope optics, in sharp contradistinction to many of his contemporaries. In reality though, the resolution of double stars is not a particularly stringent test of optics, as even so-so telescopes will manage some tricky pairs. Such tests are more a measure of atmospheric seeing and transparency than anything else. The best tests are on bright planets, especially Jupiter, which can display a rich variety of low contrast details that may prove elusive in a lesser instrument and become beautifully manifest in a higher quality telescope.

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No matter how wonderful or impressive the telescope being employed, without a sturdy mount, its powers will be greatly compromised. Denning considers both alt-azimuth and equatorial mounting systems, favouring the latter for high resolution projects, although stressing that high quality work can be done with simple non-driven mounts. Mr. Denning estimates that with an undriven, altazimuth mount, roughly 50 per cent of the observer’s time has to be expended adjusting the telescope in order to keep the object centred in the field, particularly if one is examining an object at high magnifications. In the end though, he cautions that a determined individual can make do with very simple equipment, and, in time, the observer “will gain patience and perseverance which will prove a useful experience in the future.”

pp 55.

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Author’s note: Denning actually opted for simplicity over technical sophistication with his own telescope, a 10-inch With-Browning Newtonian. It was mounted on a good but sturdy alt-azimuth mount, equipped with slow motion controls. By all accounts the instrument was permanently exposed to the elements (as evidenced by comments he made on page 76), the optics and tube assembly covered over when not in use. Denning’s telescope was thus in a permanent state of acclimation with its environment. No cooling fans were used with the telescope, as they were not available at the time, and indeed, were never really necessary.

While some modern amateurs would balk at this modest setup, it pays to remind the reader that Denning established himself as a world authority on planetary observing – particularly Jupiter and Saturn and their satellite systems – contributing a great body of knowledge in the form of drawings and written descriptions of his observations.

That Denning chose this setup over something more sophisticated reinforces an old maxim, that the quality of the observer is far more important than the type of equipment employed, a maxim that resonates strongly with this author’s ethos. This is especially true today when the amateur can enjoy high-quality mass-market optics at very reasonable prices. Denning’s estimate of the time lost in active observing must be tempered by the fact that the oculars he employed had very much smaller fields than those enjoyed by amateurs today, many of which can cover several times the area of sky he would have routinely encountered, thus reducing the time needed for object centering and adjustment.

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It is in this chapter also that Denning advances a brief but most engaging commentary on eyepieces;

Good eyepieces are absolutely essential. Many object-glasses and specula have been deprecated by errors really originated by the eyepiece. Again, telescopes have not infrequently been blamed  for failures through want of discrimination  in applying suitable powers. A consistent application of powers, according to the aperture of the telescope, the character of the object, the nature of the observation, and the atmospheric conditions prevailing at the time, is necessary to obtain the best results.

pp 46.

Denning describes the three most common oculars available to amateurs in his day: the negative, or Huygenian, the positive, or Ramsden, both of which had narrow fields of view and worked best at large relative apertures. he also mentions the Kelner, which afforded much wider fields of view (typically 40 or 50 degrees) for deep sky viewing and decent definition at relative apertures at f/6 and higher. Mr. Denning is sceptical of the claims of some telescope makers and users who have stated that their telescopes can bear powers of up to 100 per inch of aperture:

Telescopes are sometimes stated to bear 100 to the inch on planets, but this is far beyond their capacities even in the best condition of air. Amateurs soon find from experience that it is best to employ those powers that afford the clearest and most comprehensive views of the particular objects under scrutiny. Of course, when abnormally high powers are mentioned in connection with an observation, they have an impressive sound, but this is all, for they are practically useless for ordinary work. I find that 40, or at most 50 to the inch, is ample, and generally beyond the capacity of my 10-inch reflector.

pp 47

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Author’s note: Better oculars were invented in the mid to late 19th century, particularly the Plossl and orthoscopic, but owing to the greater number of un-coated elements, they were not commonly employed by amateur astronomers in Denning’s day. In respect to his comments regarding the 100x per inch claims by some observers and telescope sellers, this was a reasonable conclusion to draw, as one finds from experience that such high powers are indeed disadvantageous to delivering the best planetary images, especially in moderate and large aperture telescopes. Denning finds that 40-50x per inch of aperture to be the maximum upper limit for the vast majority of applications, and this remains true to this day. Indeed, we find that Denning commonly employed a power of 252 diameters on his 10-inch Newtonian in pursuing his studies of the bright planets, corresponding to ~ 25x per inch of aperture, in agreement with the recommendations of the majority of planetary observers even today. Indeed, it is only in the pursuit of the most difficult double stars and small planetary nebulae that higher powers are found to be useful, and only on the best nights.

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After these comments, Denning shares with us the details of a curious practice, apparently popular with dedicated observers for at least a century; using a single lens as an eyepiece:

A great advantage, both in light and in definition, results in the employment of a single lens as eyepiece. True, the field is very limited, and, owing to the spherical aberration, the objects so greatly distorted near the edges that it must be kept near the centre, but, on the whole, the superiority is much evident.

pp 47

Mr. Denning informs us that some distinguished observers, such as the Reverend William Rutter Dawes and Sir William Herschel had also noted an improvement in light grasp and distinctness employing the same technique.

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Author’s note:

Though we take so much for granted today, with our high quality optical glass, free of striations and other artifacts, broadband multi-coatings and the like, the glass out of which these early oculars were constructed would surely have been inferior to even the ‘budget’ oculars we enjoy today. The complete lack of anti-reflection coatings would have generated ghost-images due to internal reflections, especially on bright objects, cutting down on contrast and definition of low contrast details. Adopting a singlet would have greatly reduced these effects at the expense of introducing horrid off-axis aberrations.

This author once experimented with a modern ‘ball eyepiece’, that is, a single, spherical eye lens, and while the definition at the centre of the field was very nice, off axis images were very badly distorted. In the end, it was considered more a novelty than a useful tool and has not been used since.

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Denning recommends that the observer acquire three eyepieces, corresponding to low, medium and high power, appropriately chosen to match the aperture of the telescope, and cautions that the magnifications they profess to deliver may not in fact be the values they generate. He offers a means of experimentally determining actual magnifications described on pages 49-50. Denning continues by discussing the curious custom adopted by some telescope makers of using magnifying power as a ‘sales pitch’. Surprisingly, Denning identifies the famous maker, James Short (1710-68), as the individual who originated this dubious consuetude, who made his fortune selling small Gregorian-type reflectors, and which has sadly endured at least for so-called ‘department store’ telescopes right up to the present day.

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An ornate, table top Cassegrain reflector by James Short, dating from the mid-18th century.

An ornate, table top Gregorian reflector by James Short, dating from the mid-18th century.

A curious aside: Denning owned a 4-inch Gregorian telescope by Watson, similar to the instrument shown above, which, although over a century old at the time, had speculum metal mirrors that were still in good condition.

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The importance of observing in comfort (pages 53-54) is a subject very close to Denning’s heart and, accordingly, he stresses the importance of using a chair while observing and even mentions some innovations made by amateurs published in the English Mechanic. He also reveals that for objects located high overhead, a small step ladder was found to be very useful  with his 10-inch Newtonian. Comfort is of paramount importance in gaining the maximum enjoyment from an observing experience and can even make the difference between seeing something and not at all.

Beginning on page 55 and ending at the top of page 57, Denning remarks on the ‘character’ of the observer. Variations in visual acuity account for some of the discrepancies reported by observers, as well as their level of experience. Some individuals will see more than others. Historically, these differences have sometimes led to controversy:

….as a rule, amateurs should avoid controversy, because it rarely clears up a contested point. There is argument and reiteration, but no mutual understanding or settlement of the question at issue. It wastes time, and often destroys that good feeling which should subsist amongst astronomers of ever class and nationality…. paltry quibblings, fault finding, or the constant expression of negative views, peculiar to sceptics, should be abandoned, as hindering rather than accelerating the progress of science….. There are some men whose reputations do not rest upon good or original work performed by themselves, but rather upon the alacrity with which they discover grievances and upon the care they bestow in exposing trifling errors in the writings of their non-infallible contemporaries.

pp 56

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Author’s note: There is nothing new under the Sun, and Denning’s comments are as true today as the day they were written. We are all fallen, all of us wretched, and in need of redemption. And yet, we can rise above it all and do great things. Men vainly look to the heavens in search of people among the stars, yet the only ‘aliens’ we will ever encounter are our neighbours. We need to get on with each other.

Denning himself was the subject of controversy concerning some of his ideas on meteor radiants. He held some erroneous views but was bitterly attacked by some of his contemporaries, just to ‘prove’ that they were ‘right’ and he was ‘wrong.’ They wounded him deeply. This is likely one of the reasons why he withdrew from public life at the height of his career.

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On page 58, Denning discusses the practice of stopping down, i.e. the act of deliberately reducing the effective aperture by means of a ‘stop.’ The practice was sometimes done to increase the defining power of the telescope, which, for clarity, we shall equate with image sharpness, but the underlying reason for this was thought by some to be caused by blocking off a defective part of the object glass or speculum. Denning however, offers us another explanation; the atmosphere and its effects on the fielded aperture. While it is true that stopping down could mask a figuring error (more likely to occur at the edges of the objective), Denning’s own experiments seemed to favour the idea that large apertures can often benefit from stopping down on nights of poor or average seeing because smaller apertures are less affected by atmospheric turbulence than larger ones. He suggests that, for visual use, apertures of 18 inches and over can quite often benefit from an aperture stop of 16- or 14-inch stop. But he cautions that the practice is of little value in the case of moderate aperture;

With my 10-inch reflector, I rarely, if ever, apply stops, for by reducing the aperture to 8 inches the gain in definition does not sufficiently repay for the serious loss of light. But in the case of large telescopes, the conservation of light is not so important, and a 14-inch or 16-inch stop may be frequently employed on an 18-inch with striking advantage.

pp 58

In a curious note under the subtitle, Cleaning Lenses, Denning tangentially discusses some of the properties of silvered mirrors, in particular, the factors that may prolong the life of the thin silver layer. He notes that keeping the mirror dry is of benefit, as well as placing a protective cap over the optics when not in use. He claims that Calver was aware that some silvered glass mirrors held their reflectance longer than others and was related to the frequency with which the instrument was used and the environment in which it was fielded. Some mirrors held their reflectivity well for a decade or more, but this was apparently the exception rather than the rule. Intriguingly, he also states that the tarnish accumulated on silvered mirrors can work surprisingly well on lunar and planetary targets:

A mirror that looks badly tarnished and fit for nothing will often perform wonderfully well. With my 10-inch in a sadly deteriorated state I have obtained views of the Moon, Venus and Jupiter that could hardly be surpassed. The moderate reflection from a tarnished mirror evidently improves the image of a bright object by eliminating the glare and allowing the fainter details to be readily seen.

pp 60

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Author’s note: When silver tarnishes it generally leaves a tan coloured film owing to the formation of silver sulphide, which can indeed reduce the relectivity of the mirror, but the moderate deterioration Denning speaks of seemed to enhance his views of the Moon and bright planets. I believe that this can be attributed to a filter-like or ‘apodising’ effect. As this author has commented on elsewhere, filters work superbly well on moderate and large aperture telescopes owing to their ability to suppress glare and enhance the visual appearance of  subtle details that would otherwise be ‘washed out’ in the unfiltered image. This author has previously alerted readers to the benefits of employing a simple and inexpensive neutral density filter to improve the planetary images in large reflectors. More sophisticated filters, such as a polariser, also work very well in this regard. The Televue bandmate planetary filter was also found to work brilliantly on the author’s 8-inch Newtonian, which he employs routinely  to observe Jupiter. Filters are capable of adding a whole new dimension to the art of visual observing; an effect serendipitously ‘discovered’ by Denning.

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The remaining pages of this chapter are devoted to miscellaneous topics, including dewing up and cooling down of telescope optics, the celestial globe, presumably a fore-runner of the modern planisphere, the utility of opera glasses and finally a brief description of a new type of observatory showing up the length and breadth of the country; the Romsey. Unlike the all-brick, monolithic, cathedral-like domes housing the great refractors of the day, the Romsey offered a much more economical means of housing one’s telescope and keeping all one’s ancillary equipment in a single place.

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Chapter IV Notes on Telescopic Work

Covering pages 66 through 86

In this invaluable chapter, Mr. Denning provides a distillation of his practical experience in the field. He begins by suggesting that the would-be astronomy enthusiast gain some background knowledge of the objects he/she wishes to devote time to. This can be achieved by reading up on the general descriptions provided by trusted authorities in the field. But theory ought to be a guide and not an absolute means to an end, for Denning seems to value practical knowledge over that learned in books:

An observer should take the direction of his labours from previous workers, but be prepared to diverge from acknowledged rules should he feel justified in doing so from his new experiences.

pp 68

Denning feels that the observer ought to prepared for a night of observing, by making up a suitable list of objects he/she wishes to study. It need not be long and over-elaborate, nor should such a list be over ambitious.  A few objects studied well is far better than several dozen casually visited.

When no such preparation is made much confusion and loss of time is the result. On a cloudy, wet day, observers often consider it unnecessary to make such provision and they are taken at a great disadvantage when the sky suddenly clears. A good observer, like a good general, ought to provide, by proper disposition of his means, against any emergency. In stormy weather, valuable observations are often permissible if the observer is prompt, for the definition is occasionally suitable under such circumstances.

pp69

Denning estimates that the British climate offers about 100 hours of exceptional seeing per year, considerably more than is commonly believed today, but these are not confined to just a few nights, but occur sporadically over the course of the weeks and months, for he says that a night might start out with decidedly mediocre seeing only to be found to be considerably improved just a few hours later.

Denning claims that an east wind is often detrimental to viewing high resolution targets, but does not consider this to be an absolute. He differs from the general opinion expressed by contemporary astronomers in claiming that windy weather can often bring very good seeing:

I have sometimes found in windy weather after storms from the west quarter, when the air has become very transparent, that exceptionally sharp views may be obtained; but unfortunately, they are not without drawbacks, for the telescope vibrates violently with every gust of wind and the images cannot be held long enough for anything satisfactory to be seen.

pp 69

Denning mentions the favourable conditions that often attend hazy skies:

Calm nights when there is a little haze and fog, making the stars look somewhat dim, frequently afford wonderfully good seeing….. The tenuous patches of white cirrus cloud, which float at high altitudes will often improve definition in a surprising manner, especially on the Moon and planets.

pp 69.

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Author’s note: Denning’s knowledge was gained actively, in the field, more so than any of his contemporaries, for how else could he provide such extraordinary (and mostly correct) insight? Denning’s telescope was in a constant state of preparedness, as it was permanently fielded in the open air. He was thus ready to take advantage of any change in the weather that may have come about and use it to his advantage. Such knowledge cannot be learned from a book. That Denning entrusted experience over theory resonates well with this author’s own findings, especially in relation to double stars, where striking discrepancies between field observations and the prognostications of individuals posing as ‘theorists’ have been uncovered. Indeed, in some of these cases, the differences between theory and experiment have been totally irreconcilable.

Iustitia, iustitia, iustitia!

Beware of theorists posing as observers!

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Mr. Denning next discusses vision and its relation to telescopic observation. He concedes that there is much inter-individual variation among the visual acuity of individuals, with some displaying remarkable vision and others seeing much less. He mentions a one Dr. Kitchiner, who claimed that the eye of a dedicated telescopist aged 47 is as much impaired as an ordinary individual aged 60! Denning is somewhat sceptical of that claim stating that, “the Doctor’s opinion is not generally confirmed by other testimony, the fact being that the eye is usually strengthened by special service of his character.”

Further, he states:

Before the observer may hope to excel as a telescopist it is clear that a certain degree of training is requisite. Many men exhibit very keen eyesight under ordinary circumstances, but when they come to the telescope are hopelessly beaten by a man who has a practised eye. On several occasions the writer was most impressed with evidences of extraordinary sight in certain individuals, but upon being tested at the telescope they were found very deficient, both as regards planetary detail and faint satellites.Objects which were quite conspicuous to an experienced eye were totally invisible to them.

pp 71

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Author’s note: Denning’s comments agree with the experiences of this author. On many occasions over the years, I have attempted to show my students some of the delights of the second heaven, only to discover that, although they have decidedly better eyesight than my own, were unable to ‘see’ the duplicity of test double stars, plainly seen with my own eyes. Only after pointing it out and after prolonged scrutiny did they come to ‘see’ what was plainly visible. The same is true of the Great Red Spot.  Experience is a far better tool than raw visual acuity. Seeing is most definitely an art that must be learned.

I believe this also has implications for those that have derided the classical achromat, despite an enormous body of evidence demonstrating that their users (who’s eyes were trained) saw far more than what is commonly reported in the contemporary ‘literature.’ Indeed they appeared to have seen things that still largely elude the majority of self-proclaimed veterans.

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On page 72-73, Mr. Denning stresses the importance of note making. The content of these notes need not be elaborate, just a few salient points about the date, time and seeing conditions, the instrument fielded and some brief written details on the objects observed. Denning recommends that such notes be made as close to the time of observation as possible. “If the duty is relegated to a subsequent occasion,” he says, “it is either not done at all or done very imperfectly.”  Something ‘trivial’ recorded on an earlier date may turn out to be very important at a later date.

Denning also recommends sketching what one sees at the telescope, even if the would be observer is not skilled in such activities. They need not be works of art but simply show the ‘definite’ features of the object under scrutiny. With time, the note maker/sketcher becomes a “draughtsman:”

My own plan in sketching at the telescope  is to first roughly delineate  the features bit by bit  as I successively glimpse them, assuring myself, as I proceed, as to the general correctness in outline and position, then, on completion, I go indoors to a better light and make copies while the details are still freshly impressed on the mind.

pp 74

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Author’s note: It is a sad state of affairs that the noble art of note making is in decline; perhaps terminally. Many amateurs do not make any notes of any description. More’s the pity, for notes provide a means of assessing progress over time, and form the bedrock of an amateur’s experience under the starry firmament. They are an integral part of the culture of amateur astronomy and can prove invaluable in resolving issues that sometimes appear contradictory, especially if one is viewing through different instruments at different times. An observer without notes is liable to make the same mistakes over and over again.

An observer without notes has no past.

Sketching is also an enjoyable and invaluable way of preserving information and when conducted over a long period of time, can prove to be of vital importance, especially if one records something novel. There is no ‘right’ or ‘wrong’ way to sketch. Denning preferred to sketch the basic features of his subjects at the telescope, while refining them indoors a short time afterwards. Others choose to scrutinise the object intently, committing to memory all the detail one can capture before returning indoors to perform the sketch. Find the method that works best for you.

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In a section called “Friendly Indulgences,” Denning recognises the need for outreach and to be gracious to friends and the curious passerby, who express an interest in viewing an astronomical object. But in the end, he feels that there is a fine line between getting on with one’s observing and being a “showman.” One comes away with the feeling that he was, for the most part, a solitary observer, who was happy in his own company and would rather get on with things than engage in some lengthy discussion with someone else while the sky remained clear:

Of course it is the duty of us all to encourage a laudable interest in the science, especially when evinced by neighbours or acquaintances; but the utility of an observer constituting himself a showman, and sacrificing many valuable hours which might  be spent in useful observations, may be seriously questioned. The weather is so bad in this country that we can ill spare an hour from our scanty store.

pp 74.

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Author’s note: One cannot help but wonder what Denning would have thought of the star parties amateurs attend these days. I suspect he would have kept well away from them. While star parties can be fun and provide a means of looking through various kinds of telescope to assist making a decision on a future purchase, our hobby is still, by and large,  a solitary passtime. We must remember that for every lion among us there is also a leopard.

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Denning discusses the realities of open air observing, wittily commenting that a shiny new telescope tube exposed to the elements of nature will soon lose its “smart and bright appearance”, although the views will remain as good as they always were. It is here also that the forgotten Bristolian reveals his great love affair with the heavens, providing vivid descriptions of the physical conditions he had to endure night after night. Because he remained a bachelor all his life and thus, had no dependants, his life could be best be likened to that of a monk, wedded as it were to his astronomical investigations. As a dedicated meteor observer, he spent endless hours on every clear night recording their brilliant tracks across the sky. This kind of work is not for the faint hearted, especially in the cold of winter. Denning describes his lot vividly:

Night air is generally thought to be pernicious to health; but the longevity of astronomers is certainly opposed to this idea. Those observers who are unusually susceptible to affections of the respiratory organs must of course exercise extreme care, and will hardly be wise in pursuing astronomical work out of doors on keen, wintry nights. But others, less liable to climatic conditions, may conduct operations with impunity and safety during the most severe weather. Precautions should always be taken to maintain a convenient degree of warmth; and for the rest, the observer’s enthusiasm must sustain him. A “wadded dressing gown” has been mentioned as an effective protection from cold.  I have found that a long, thick overcoat, substantially lined with flannel, and under this a stout cardigan jacket, will resist the inroads of cold for a long time. On very trying nights, a rug may also be thrown over the shoulders, and strapped round the body.  During intense frosts, however, the cold will penetrate (as I have found during prolonged watches for shooting stars) through almost any covering. As soon as the observer becomes uncomfortably chilly, he should go indoors and warm his things before a fire.

pp 75.

After relating many humorous stories about finding wee beasties taking up residence inside his telescope tube, Denning returns to more pressing matters, emphasising that an observer eager to discover something of importance must necessarily be a person of method and perseverance and not to divest too much importance to his instruments;

A skilled workman will do good work with indifferent tools; for after all it is the character of the man that is evident in his work; and not so much the resources which art places in his hand.

pp 80

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Author’s note: The old adage is true: a bad workman always blames his tools. Today, we are blessed to have vastly superior ‘tools’ to anything Mr. Denning could have dreamed of. And yet, all the while, we seem to want  more and more. Fortunate indeed is the man who is happy with his tools!

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In the final pages of this interesting chapter, Denning discusses the potential of photography to revolutionise the science of astronomy. His opinions are brief but he was essentially correct about its growing prowess, but since very few amateurs had the means of conducting photographic studies of the heavens at that time, he does not dwell on the topic.

The author encourages his readers to follow the astronomical literature, and recommends all the greats of the age including the Reverend T.W Webb’s,Celestial Objects for Common Telescopes, Chamber’s Descriptive Astronomy and Noble’s, Hours with a 3-Inch Telescope, as well as more specialised texts. He also encourages his readers to consult practical periodicals of the day, especially the English Mechanic, Nature and Knowledge. 

Denning encourages those who live in towns and cities to get out and do some observing, explaining that the conditions can be quite good, especially for viewing the Moon and the planets. He mentions that smoggy conditions may actually aid in bringing out detail on the planetary bodies:

I have frequently found planetary markings very sharp and steady through the smoke and smog of Bristol. The interposing vapours having the effect of moderating the bright images and improving their quality.

pp 81.

He ends this chapter on an enthusiastic note:

A telescope may either be employed as an instrument of scientific discovery and critical work, or it may be made a source of recreation and instruction. By its means the powers of the eye are so far assisted and expanded that we are able to conceive of the wonderful works of the Creator than could be obtained in any other way.

pp 86.

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Author’s note: The population of Bristol, where Denning lived for most of his life, quintupled during the 19th century, reaching 330,000 by 1901. The burning of coal would have been the main source of energy driving commerce and heating households, and so smog would have been a common phenomenon especially during still winter nights in the city.

Denning yet again mentions the beneficial effects of dimming the image as regard gleaning more defining power from planetary bodies. I cannot help but think that were he alive today, he would have been an enthusiastic proponent of filters in the planetary astronomy.

Unbridled enthusiasm distinguished Denning from many of the classic authorities of his day. His tone was approachable, unpretentious and reassuringly upbeat. What he saw through his telescope was his reaction to the natural wonders created by the Living God, who placed these things in heaven so that we might marvel at them and be reminded of His omnipotence. In this capacity, he was a kindred spirit, who saw no conflict between scientific investigation and his personal faith.

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Chapter V: The Sun

Covering pages 87 through 112

We now begin to explore the late 19th century knowledge of the heavenly bodies, one by one, beginning with the Sun. As a guide, this author will bring to bear his experiences with a telescope not too dissimilar to Denning’s own; a 8″ f/6 Newtonian on a modern alt-azimuth mount, which has given him wondrous views of the firmament.

Jupiter as it appeared at 10:00pm local time on the evening of May 5, 2016. Magnification 200 diameters.

Jupiter as it appeared at 10:00pm local time through a 8″ f/6 Newtonian on the evening of May 5, 2016. Magnification 200 diameters.

 

 

 

 

 

 

 

 

 

 

The opening pages of this chapter discuss basic solar facts, as true today as they were in Denning’s time. The Sun, we learn, has a mean distance from the Earth of about 92,900,000 miles, computed from a solar parallax of 8.8″, and a diameter of 866,000 miles. Interestingly, Denning provides a series of micrometer measures (pp 88) of the solar disk diameter, showing that it varies from 32 minutes 66 seconds at the end of December, to 31 minutes 32 seconds at the end of June. This reflects the slight ellipticity of the Earth’s orbit, carrying our planet slightly closer to the Sun in mid-winter in the Northern Hemisphere  and a little further away in mid-summer.

Denning relates the fact that the most conspicuous feature of the solar disk – sunspots – were likely seen throughout antiquity, and among observers from a number of civilizations. The earliest account offered by the author dates to 188AD. These spots were seen by the naked eye through dense fog, most commonly at sunrise and sunset. Denning himself speaks of observing four large spots (pp 89) on a foggy autumnal evening in 1870, just as the Sun was setting. He claims that if these spots are bigger than about 50″, they should be picked up by the average eye.

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Author’s note: Although a curious visual phenomenon, this author strongly advises that the reader not look at the Sun even in the very foggy conditions described above. Many a tyro has damaged his/her eyes in doing so.

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Denning is reluctant to attribute the telescopic ‘discovery’ of sunspots to any one individual but mentions, in particular, various early telescopists including, Fabricius, Galilei, Harriot and Scheiner, as claiming the limelight. He also corroborates later accounts by historians of astronomy, who claim that England’s Thomas Harriot saw these spots telescopically as early as December 8, 1610:

“The altitude of the Sonne being 7 or 8 degrees, and it being a frost and a mist, I saw the Sonne in this manner.”

pp 90.

He also mentions a drawing made by Harriot, showing three large sunspots. Thus, Denning was probably aware of Harriot’s early telescopic observations; possibly predating those made by Galileo Galilei.

The most common way in which observers in Denning’s day observed the Sun was to employ deeply coloured glass of various ‘depths’; either red or green, placed at the focal plane, together with a Herschel wedge, invented in 1830 by Sir John Herschel. Denning claims that red tinted glass is inferior to its green tinted counterpart:

The diagonal, by preserving a part only of the solar rays, which are transmitted by the object glass. This little instrument is comparatively cheap, and no telescope is complete without one.

pp 92.

Denning suggests that a small telescope, a refractor of 3- or 4-inch aperture, or a reflector of no more than 4-inches, are best employed in solar studies and recommends that larger instruments be stopped down to improve definition. He also mentions, owing to the great natural brilliance of the Sun, that unsilvered mirrors are perfectly adequate for obtaining good solar images.

With comfort and safety never being far from the mind of the author, Denning stresses that the solar observer be shaded from the Sun’s burning rays as much as is practical. He also recommends keeping the ‘solar telescope’ in the shade to ensure it does not induce the annoying thermals that can destroy high-definition features. As regard suitable magnification, he suggests that a power of about 60 and a field of view of just over half an angular degree is desirable to get a good ‘whole disk’ perspective. Higher powers can prove usual to gain better images of smaller features, though he does not recommend magnifications higher than about 150x. Once again, Denning mentions using a singlet eyepiece (presumably the field lens of a Huygenian ocular) in obtaining high power views yielding the highest definition.

Oddly enough, Denning gives scant mention to other methods of observing the solar disk, particularly by projecting the image onto a smooth, white surface. There is one reference made to this technique, appearing on page 93-94:

At Stonyhurst Observatory excellent delineations of solar phenomena are made; and the late Father Perry, who lost his life in the cause of science, thus described the method:- “On every fine day the image of the Sun is projected on a thin board attached to the telescope, and a drawing of the Sun is made, 101/2 inches in diameter, showing the position and outline of the spots visible.

pp 93-94

Solar projection techniques were used by the very earliest telescopists, including Galileo Galilei.

In a most curious account related on page 95, Denning describes the use of a primitive reticle scale, just a graduated piece of plane glass, mounted at the focal plane of a 4-inch Cooke refractor, borrowed from a friend, with which he was able to estimate the size of a large sunspot, observed on June 19, 1889. Using this technique he calculated that the real size of the spot was 27,000 miles! This technique could also be done using projection methods.

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Author’s note: Man and his numbers! How wonderful it is to be able to measure anything! Among other reasons, our heavenly Father gave us these powers so that we could project our imagination into realms hopelessly beyond the ability of our frail bodies to experience directly. Denning was no mathematician, of course, but he did have an excellent command of numbers, as we shall see in many other references explored later in the book.

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The chapter continues with discussions on various solar phenomena, beginning with the majesty of a solar eclipse, briefly describing their prediction (saros cycles) and rarity at any arbitrarily chosen location. On page 98, the aspects of a series of 12 partial solar eclipses as seen (or imagined) from England through the years 1891 to 1922, are reproduced. This is followed by an equally brief discussion on the sunspot cycle and how it may be followed by the amateur equipped with modest equipment.

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Another curious aside: In his younger years, Denning was a keen hunter of the hypothetical planet Vulcan, explaining why he had a particular interest in all things solar. Indeed, he helped organise coordinated searches for the planet among a number of English solar astronomers. Moreover, in Chapter IV, page 85, he made two lists of (I) ‘suspected objects to be erased’, and (II) ‘objects that in the future will add to our store’. Vulcan appears in the former list, suggesting that, at the time of writing of the book, he had firmly given up on the prospect of finding an intra-mercurial planet.

The quest for Vulcan reached fever pitch in Europe and across the United States during the late 19th century, bolstered by the work of mathematical (but myopic) astronomers of the ilk of (the arrogant) Urban Leverrier(1811-77), who uncovered a small, residual perihelion shift in the position of the planet Mercury, amounting to 43 arc seconds per century. Indeed a hitherto obscure physician and amateur astronomer, Edmond Modeste Lescarbault (1814-94), claimed to have observed such a planet in March 1869 at his private observatory in the picturesque village of Orgères-en-Beauce, in Northern France. Leverrier was happy to accept him as the discoverer and formally named the planet Vulcan – after the Roman god of fire – in March 1860, which circled the Sun every 19.7 days, at a distance of about 21 million kilometres from the solar surface. But soon, the astronomical community grew sceptical of Lescarbault’s sensational ‘discovery,’ claiming that such a world, even though as small as the Moon, would have been easily visible to many astronomers who had watched the Sun for many years.

By the time Denning penned his tome, most astronomers had dismissed the notion that a ninth planet, Vulcan, really existed, even though the reason for the measurable 43” per century perihelion shift of Mercury was not yet accounted for. The explanation had to wait until Albert Einstein formulated his epochal theory of general relativity in 1915, which perfectly accounted for the Mercury anomaly. Indeed, Einstein was to later write that his heart raced when his calculations exactly explained the planet’s sojourn through the curved space near the Sun. “For a few days,” he wrote, “I was beside myself in joyous excitement.”

All the while, I cannot help but think that Denning, in the exuberance of his youth, also searched for Vulcan with “joyous excitement.”

More on Vulcan here.

From pages 100-112, Denning goes on to describe, in considerable detail, the telescopic morphology of sunspots as well as their distribution on the solar surface. He provides an accurate an essentially modern value for the solar rotation period of ~25 days and 8 hours. It was also known to him that the rotation period varies with solar latitude, thus providing good evidence (like Jupiter, discussed later) for its essentially gaseous nature. On page 105, Denning presents a list of historically interesting astronomers and their estimates of the solar rotation rate from Cassini (1678) to Wilsing (1888), showing that such knowledge was known for nearly two centuries.

Denning displays his voluminous knowledge of solar phenomena in these closing pages of Chapter V, including the work of many astronomers – both contemporary and historical – as well as his some of his own detailed observations carried out with a 4-inch glass. This includes a discussion on solar faculae, prominences and historically significant eruptions, as well as some observational anomalies including spots noted at unusually high solar latitudes;

Mechain saw a spot in 1780 having a latitude of 401/3 degrees; in April 1826 Cappoci recorded one having 49 degrees of S. latitude Schwabe and Peters observed  spots 50 degrees from the equator. Lahire, in the last century, described a spot as visible of 70 degrees; but the accuracy of this observation has been questioned.

pp111.

Finally, on page 112, Denning provides a curious reference to a quantitative brightness differential between the solar limb and its centre, a measure previously unknown to this author:

In observing the Sun with a telescope the amateur will soon notice that the surface is far more brilliant in the central parts than round the margin of the disk. Vogel has estimated that immediately inside the edges the brightness does not amount to one seventh that of the centre.The difference is entirely due to the solar atmosphere, which is probably very shallow relatively to the great diameter of the Sun.

pp 112

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Author’s note: The Sun is, by and large, composed of a fourth form of matter called plasma. At temperatures in excess of a few thousand Kelvin, atoms break up to form a ‘soup’ of charged particles consisting of electrons, protons and an assortment of atomic nuclei. It is this moving plasma that generates the Sun’s prodigious magnetic field and all its associated phenomena.

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Chapter VI The Moon

Covering pages 113-136

Early in autumn, when the evenings are frequently clear, many persons are led with more force than usual to evince an interest in our satellite, and to desire information which may not be conveniently obtained at the time. The aspect of the Moon at her rising, near the time of the full, during the months of August, September, and October, is more conspicuously noticeable than at any other season of the year, on account of the position she then assumes on successive nights, enabling her to rise at closely identical times for several evenings together. The appearance of her large, ruddy globe at near the same hour, and her increasing brilliancy as her horizontal rays give way under a more vertical position, originated the title of “Harvest Moon,” to commemorate the facility afforded by her light for the ingathering of the corn preceeding the time of the autumnal equinox.

pp 113

It is with such wonderful prose that Denning opens his chapter on observing our closest neighbour in space. Denning was a man happy to be in the open air, either with telescope or with his unaided eyes, observing the grand spectacles of the heavens. In the proceeding paragraphs, he clearly outlines why the Moon is of such critical importance to life on Earth, in issuing the tides, for example, and stabilising the Earth’s climate. But he also notes its importance, since time immemorial, in human time keeping, as well as how its welcome light assisted the plight of navigators of the seven seas.

What follows thereafter are some basic physical facts about the Moon. For example, he states the apparent size of the Moon at apogee and perigee (29’21” and 33’5”, respectively), though he appears to have mistakenly stated these the wrong way round on page 114. The lunar diameter he quotes – 2160 miles – and its mean distance from the earth – 237,000 miles – are essentially those of the modern value.

Denning then launches into a general overview of the lunar regolith as seen through a good telescope;

When we critically survey the face of the Moon with a good telescope, we see at once that her surface is broken up into a series of craters of various sizes, and that some irregular formations are scattered here and there, which present a similar appearance to mountain ranges. The crateriform aspect of the Moon is perhaps the more striking feature, from its greater extent; and we recognise in the individual forms a simile to the circular cavities formed in slag or some other hard substances under the action of intense heat. In certain regions of the Moon, especially near the south pole, the disk is one mass of abutting craters, and were it not for the obvious want of symmetry in form and uniformity in size, the appearance would be analogous to that of a giant honeycomb. These craters are commonly surrounded by high walls or ramparts, and often include conical hills rising from their centres to great heights. While the eye examines these singular structures, and lingers amongst the mass of intricate detail in which the whole surface abounds, we cannot but feel impressed at the marvellous sharpness of definition with which the different features are presented to our view. It matters not to what district we direct our gaze, there is the same perfect serenity and clearness of outline. Not the slightest indication can be discerned anywhere of mist or other obscuring vapours hanging over the lunar landscape.

pp 114-115

Denning correctly states that the Moon is devoid of an atmosphere and probably doesn’t have water, in spite of the many ‘seas’ that adorn lunar maps. On page 115 through 116, Denning presents an explanation for why the Moon shows the same face toward the earth throughout its cycle (it is almost completely tidally locked) and presents the interesting phenomenon of libration, where the lunar countenance can show up to 59 per cent of its surface over the course of its earth orbit.  Denning also mentions the wonderful phenomenon of earthshine, the “ new Moon in the old Moon’s arms,”  and how the observers of old remarked that a waning Moon showed this earthlight more strongly than the new Moon.

The chapter continues by discussing the kinds of instruments best suited to lunar work, for the casual as well as the more serious observer:

A small instrument with an object glass of about 2 ½ inches will reveal a large amount of intricate detail on the surface of our satellite, and will afford the young student many evenings of interesting recreation. But for a more advanced survey of the formations, with a view to discover unknown objects or traces of physical change in known features, a telescope of at least 8 or 10 inches is probably necessary, and powers of 300 to 350, and more.

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Author’s note: Yet again, Mr. Denning dispenses sterling advice to the would-be student of the Moon that is entirely in agreement with all subsequent authorities on the subject. You’ll see more with a larger telescope and will be able to use higher powers to ferret out the finer details. Such advice appears to have been lost on a current subsection of amateurs who are willing to squander a veritable fortune for small refractors of very limited aperture. Such are the times we live in!

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On pages 118 and 119, Mr. Denning discusses the fascinating phenomenon of a lunar eclipse, their frequency and appearance, both telescopically and to the naked eye. Here we find some invaluable historical records of how the intensity of a total lunar eclipse varied from apparition to apparition, with references to observations conducted by astronomers dating back nearly nine centuries. While some total lunar eclipses were spectacularly bright, with a beautiful, coppery orb being clearly visible to the naked eye, at other times, the eclipsed Moon completely disappeared:

On May 5 1110, Dec.9, 1620, May 18, 1761, and June 10, 1816, our satellite is said to have become absolutely imperceptible during eclipse. Wargentin, who described the appearance 1761, remarks:- “The Moon’s body disappeared so completely that not the slightest trace of any portion of the lunar disk could be discerned, either with the naked eye or with a telescope.”

pp 119.

 Denning recalls his own observations of a peculiarly dim lunar eclipse:

On Oct. 4 1884, I noticed that the opacity was much greater than usual; at a middle period of the eclipse the Moon’s diameter was apparently so much reduced that she looked like a dull, faint, nebulous mass, without sharply determinate outlines. The effect was similar to that of a star or planet struggling through dense haze.

pp 119

In contrast, Denning describes the eclipse of March 19, 1848 as unusually bright:

The Moon presented a luminosity quite unusual. The light and dark places on the face of our satellite could be almost as well made out as an ordinary dull moonlight night.

pp 119.

In addition to these records, Mr. Denning mentions some explanations for the variability of the intensity of such eclipses. In particular, he describes a theory first suggested by the great German astronomer and mathematician, Johannes Kepler, who attributed this variability to differences in the humidity of the atmosphere, as well as more contemporaneous explanations proffered by a one Dr Burder, who attributed such changes in the activity of the solar corona.

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Author’s note: Mr. Denning did not mention the considerable effects of atmospheric dust, which has a known reddening effect on astronomical bodies, e.g. sunsets, owing to a phenomenon known as Rayleigh scattering. His description of the unusually dim appearance of the lunar eclipse of October 4 1884, could be explained by the Volcanic eruption of Krakatoa, Indonesia, in August 1883, which would have ejected a considerable mass of dust into the Earth’s upper atmosphere, causing freak meteorological conditions well into 1884.

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Our satellite presents such a wealth of intricate detail through a Newtonian of moderate aperture, that it is scarcely possible to describe the impact with which it assaults the eye on a clear and tranquil night. The images of the Moon at moderate and high power through this author’s 8-inch f/6 Newtonian would have been broadly comparable to what Mr. Denning saw and recorded so diligently, that it is possible, at least to some degree, to ‘re-live’ the visual extravaganzas he remarks upon in the subsequent pages of his chapter on our faithful satellite in space.

While there is little doubt in Denning’s mind that the Moon is, to all intents and purposes, geologically dead, he is of the opinion, like so many other dedicated lunar observers before and after him, that changes can and do occasionally occur on its surface. Pages 120 through 123 recount a number of observations carried out by historical figures concerning this perennially interesting subject, beginning with the views of Sir William Herschel, who conducted extensive lunar observations using his “most excellent” 6.3 inch Newtonian reflector of 7 foot focus. On page 120 he reproduces Herschel’s lunar observations dated to April 1787:

“I perceive three volcanoes in different places of the dark part of the New Moon. Two of them are already nearly extinct, or otherwise in state of going to break out, the third shows an eruption of fire or luminous matter.”

pp 120.

But other observers soon offered less far-fetched explanations of these ‘fiery’ structures, particularly Schröter, who in fact used an identical 7 foot reflector to that employed by Herschel, suggesting they were due to reflected light from the Earth falling upon elevated spots of the Moon  having ” the unusual capacity to return it.

Denning’s contemporary, Wilhelm Tempel, of comet fame, reported what he thought was an impact of some sort on the evening of June 10, 1866, near the locus of the great crater Aristarchus;

“Of course,” he wrote, “I am far from surmising a still active chemical outbreak, as such an outbreak supposes water and an atmosphere, both of which are universally not allowed to exist on the Moon, so that the crater-forming process can only be thought of as dry, chemical, although warm one.”

pp 121.

On the same page, Denning recounts the extraordinary tale of the German astronomer Johann Friedrich Julius Schmidt (1824-1885), who claimed that the 5.5 mile diameter crater Linné had completely disappeared in 1866;

He averred that he had been familiar with the object as a deep crater since 1841 but in October 1866 he had found its place occupied by a whitish cloud. This cloud was always visible but the crater itself appeared to have become filled up, and was certainly invisible under its former aspect.

pp 121.

Denning discusses the observations of other observers, who took Schmidt’s report seriously, but in the end, the lack of confirmation led him to think that it was a trick of light. On page 122, he also relates the case of a one Dr. Klein, who, in contrast to Schmidt, reported the actual appearance of a “deep, dark crater” – about 18 miles to the west-northwest of Hyginus! This time, Denning himself had a look at the region with his 10-inch With-Browning Newtonian, but like many of his contemporaries, described it as a “saucer like depression” rather than the “sharply cut, deep crater” described by Klein

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Authors note: Schmidt’s observations caused international controversy for several decades, drawing the attention of many astronomers of repute. But while Schmidt had established himself as a careful and experienced observer, in the end the case was considered unproven. It is now known that the visibility of this crater is highly dependent on seeing conditions, being all but invisible under poor conditions of seeing.

Throughout the 20th century, a sizeable fraction of lunar observers continued to search for so-called transient lunar phenomena, which basically refer to any sudden changes to the lunar surface and which have a scientific basis in meteorite impacts, lunar out-gassings and the like. The lunar enthusiast is encouraged to keep reporting such lunar anomalies, as and when they occur. But you need to get out and look to see them!

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In the next section, Mr. Denning brings to our attention to the importance of timing when it comes to observing high resolution objects on the lunar surface:

As the Sun’s altitude is constantly varying with reference to lunar objects, they assume different aspects from hour to hour. In a short interval the same formations become very dissimilar.

pp 122.

Furthermore, Denning offers the reader some excellent advice, which, sadly, is not at all stressed by contemporary lunar observers:

The lunar landscape must be studied under the same conditions of illumination and libration, with the same instrument and power, and in a similar state of atmosphere, if results are to be strictly comparable. But it is very rarely that observations can be effected under precisely equal conditions; hence discordances are found amongst the records.

pp 123.

What follows on from this is an excellent summary of the most prominent lunar visual spectacles, together with brief notes on what can be observed with a modest telescope. The importance of note taking is once again stressed, especially the local time to the nearest minute. The text is illustrated by some exquisite drawings of T. Gwyn Elger (and reproduced quite well in this inexpensive reprint!).

On page 135 Denning discusses the occultation of stars by the Moon, which, he reminds us, occur several times each month! Here he mentions something rather curious:

The stars do not always disappear instantaneously. On coming up to the edge of the Moon they have not been suddenly blotted out, but have appeared to hang on the Moon’s limb for several seconds. This must arise from an optical illusion, from the action of a lunar atmosphere, or the stars must be observed through fissures on the Moon’s edges.

pp 135

The reader is encouraged to find out how the discussion develops!

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Author’s note: One gets the strong impression that Denning was an advocate of the volcanic origin of the lunar craters, a theory that was supported well into the 20th century. This is despite the fact that the impact theory of crater formation was alive and well ever since the time of Dr. Robert Hooke (1635-1703), who was among the first to suggest the latter as a plausible, alternate theory (discussed at length in this author’s up-and-coming book, Tales from the Golden Age of Astronomy), based on experimental science.

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Chapter VII  Mercury

Covering Pages 137-144.

In the opening paragraphs of this chapter, Mr. Denning identifies Mercury as the closest planet to the Sun, though he still gives mention to the elusive planet Vulcan, discussed previously in connexion with the Sun.  He then presents the basic astronomical information about Mercury, including its orbital period, eccentricity, elongations, true and apparent diameter, which, he informs us, varies from 4.5” to 12.9” at superior and inferior conjunction, respectively. These data are essentially modern. Denning also mentions the curious fact that the great Polish astronomer Nicolaus Copernicus, never once saw Mercury!

Copernicus, amid the fogs of the vistula, looked for Mercury in vain, and complained in his last hours that he had never seen it!

pp 138.

Following on from this, Denning discloses the number of sightings of the planet he made at this point in his astronomical career:

I have seen Mercury on about sixty-five occasions with the naked eye. In May 1876, I noticed the planet on thirteen different evenings, and between April 22 and May 11, 1890, I succeeded on ten evenings. I believe that anyone who made it a practice to obtain naked-eye views of this object would succeed from about twelve to fifteen times in a year.

pp 139.

He then follows up with details of particular apparitions of Mercury, as preserved in his voluminous notes, when the planet was particularly bright and striking to the eye, such as in February 1868 and in November 1882.

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Author’s note: It is quite probably true that many an amateur astronomer has never observed Mercury, owing to its very low altitude and proximity to the Sun. Denning was a prodigious observer though and the number of sightings he mentions pays testimony to that precocity.

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With characteristically delightful prose, Denning describes the momentous first sighting of the planet in the telescope and the excitement it induces in the observer:

The first view of Mercury forms quite an event in the experiences of many amateurs. The evasive planet is sought for with the same keen enthusiasm as though an important discovery were involved. For a few evenings efforts are in vain, until at length a clearer sky and a closer watch enables the glittering little stranger to be caught amid the vapours of the horizon. The observer is delighted and, proud of his success, he forthwith calls out the members of his family that they, too, may have a glimpse of the fugitive orb never seen by the eye of Copernicus.

pp 139.

After presenting further historical titbits, he then describes the general appearance of the little planet as it appeared through his telescope;

Mercury has a dingy aspect in comparison with the bright white lustre of Venus. On May 12, 1890, when the two planets were visible as evening stars, and separated from each other by a distance of only 2 degrees, I examined them in a 10-inch reflector, power 145. The disk of Venus looked like newly polished silver, while that of Mercury appeared of a dull leaden blue. A similar observation was made by Mr Nasmyth on September 28, 1878. The explanation appears to be that the atmosphere of Mercury is of great rarity, and incapable of reflection in the same high degree as the dense atmosphere of Venus.

pp 140

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Author’s note: While some observers have reported a pinkish tinge to the planet over the years, this is indeed reminiscent of the appearance of the planet seen in various telescopes over a few decades of time by this author. Regarding Mercury’s lack of an appreciable atmosphere, Denning’s conclusion is absolutely sound. Any primordial air it might have had has long been stripped away by the solar wind. What remains now is an extremely nebulous vapour, consisting mostly of the ions of the alkali and alkaline earth metals.

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Continuing on in this chapter, Mr. Denning discusses the ways in which the enthusiast may derive the maximum amount of information from this small and somewhat elusive world. With his simple, undriven mount, he advises the would-be observer to catch the planet just before dawn and to carefully follow it as it rises higher in the sky.  He refrains from making any detailed studies until a few hours after rising however, when the disk takes on a much steadier appearance. During these better moments, he most likens Mecury to the planet Mars in terms of the dark markings and spots it presents to the trained eye. For this he employed a power of about 212 diameters with his 10-inch silver-on-glass reflector.

On page 141-2, Denning reproduces the details of a correspondence he had with the famous Italian astronomer, G.V. Schiaparelli (of Mars fame) in 1882, who, using a fine 8.5 inch Merz achromatic refractor, agreed wholeheartedly with Denning that Mercury most resembles the Red Planet, at least superficially. Two fine drawings of the planet made by the great Bristolian observer himself are presented on page 143.

Denning further discloses details of Schiaparelli’s belief that the length of Mercury’s day is the same as its orbital period, in the same way as our Moon. He does however stress that these details still required corroboration.

The final pages of the chapter discuss transits of the planet as well as an occultation of Mercury by the Moon, dating to April 25, 1838.

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Author’s note: Schiaparelli’s claims about the length of a Mercurial day were not ultimately borne out. The planet in fact takes twice as long to revolve on its axis (176 days) as it does to complete one orbit of the Sun (88 days). However, this was not determined until 1965 using radar techniques.

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Chapter VIII Venus

Covering pages 145-154

Denning begins this chapter by commenting on the illustrious beauty of Venus at dawn or at dusk, and how the ancient believed the morning and evening stars were not one and the same. As harbinger of the day, Venus was known as Lucifer by the ancient Greeks and Hesperus, when the planet appeared as an evening star. When it appeared as an evening object in the autumn of 1887, Denning recalls that many people thought that the Star of Bethlehem had returned after a 19 century hiatus. He explains that at its greatest brilliancy, the planet is reduced to a slender crescent subtending an angular diameter of 65” at inferior conjunction. And when displaying its full disk, it shrinks in both size and luminous glory, presenting a disk scarcely one seventh as large (9.5”). As anyone who has examined Venus with telescopic aid will attest, the planet can be disappointing:

When the telescope is directed to Venus it must be admitted that the result hardly justifies the anticipation. Observers are led to believe, from the beauty of her aspect as viewed with the unaided eye, that instrumental power will greatly enhance the picture and reveal more striking appearances than are displayed on less conspicuous planets. But the hope is illusive……….. There are no dark spots, of bold outline, such as we may plainly discern on Mars, visible on her surface. There is no arrangement of luminous rings, such as encircle Saturn. There are no signs of dark variegated belts, similar to those that gird Jupiter and Saturn; nor is there any system of attendant satellites, such as accompany each of the superior planets.

pp 146-7.

Nonetheless, Denning concedes that Galileo’s observations of the phases of Venus through his primitive telescopes were enough to put the Copernican principle on a firm footing.

As with observing Mercury, he recommends that Venus is best observed during the day. He then launches into a brief survey of historical observations of the planet by celebrated observers of past centuries including J. D. Cassini (1666), Bianchini ( 1726-7), Schröter (1788) and Sir William Herschel (1777-93), and observations made in his own century including, Mädler (1833) and Di Vico (1840-1). Denning recounts in detail some observations conducted by Schröter, who thought that Venus had enormous mountains, the peaks of which would occasionally penetrate the clouds and reveal their presence in the telescope.

Like Mercury, the rotation period of Venus was unknown in Denning’s day and varied enormously from 23 hours, 21 min (Cassini 1666) to 224.7 days (Schiaparelli 1880).

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Author’s note: Schiaparelli was the closest to getting Venus’ rotation period correct. At 224 days it was less than 20 days short of the modern determined value of 243 days. He deduced this time period by assuming that the planet was tidally locked owing to its closer proximity to the Sun than the Earth. We now know that Venus rotates in a retrograde direction, a result of a possible collision with a large embryonic planet early in the history of the Solar System.

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Beginning on page 150 through 151, Denning discusses the nature of the many faint markings made by observers over the years. He notes that many of these reports were made by astronomers using rather small telescopes and how observers endowed with the visual acuity of the Reverend Dawes, failed to detect any markings with the telescopes he employed. He cautions that small telescopes will often create illusory views:

Perhaps it may be advisable here to add a word of caution to observers not to be hastily drawn to believe the spots are visible in very small glasses. Accounts are sometimes published of very dark and definite markings seen with only 2 or 3 inches aperture. Such assertions are usually unreliable. Could the authors of such statements survey the planet through a good 10- or 12-inch telescope, they would see at once they had been deceived. Some years ago I made a number of observations of Venus with 2-, 3- and 41/2 inch refractors and 4- and 10-inch reflectors, and could readily detect with the small instruments what certainly appeared to be spots of a pronounced nature, but on appealing to the 10-inch reflector, in which the view became immensely improved, the spots quite disappeared, and there remained scarcely more than a suspicion of the faint condensations which usually constitute the only visible markings on the surface.

pp 151

Denning gives mention to one of Venus’ most mysterious and enduring phenomena,  referred to today as the Ashen Light; a faint ‘ashy light’ similar to earthshine seen on the Moon, when the planet is near inferior conjunction and its slender crescent is most prominently displayed. He refers to the kind of illumination as a ‘phosphoresence’. He reports that a one Zanger, based in Prague, observed a ‘coppery ring’ completely encircling the planet on a number of occasions.

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Author’s note: The Ashen Light has a very long history associated with it, dating back to the mid-17th century. One of the finest astronomical artists of the post-war era, Richard Baum, of Chester, England, produced some wonderful renderings of the Ashen Light using his beloved old 4.5 Cooke refractor, which he enjoyed for many years. In more recent times however, some unscrupulous swine stole it from him, the whole affair disturbing him so much that he gave up observing altogether. What a shame!

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The remainder of the chapter discusses alleged observations of a satellite of Venus dating from the 17th and 18th centuries. The putative Cytherean moon, unofficially named ‘Neith’, was never positively identified and the consensus among astronomers of the 19th century was that the earlier sightings were nothing more than an ignis fatuus resulting from ghost reflections from eyepieces and the like. Curiously, Denning mentions the transits of Venus which occurred in 1874 and 1882, which he himself observed and even mentions the ‘future’ transit of 2004, which would thrill a new generation of astronomers.

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Author’s note: It is noteworthy that Denning completely avoids speculating on the nature of the Cytherean environment, particularly in light of the wild speculations that were doing the rounds in the late Victorian period. Back in 1870, his compatriot, Richard A. Proctor (1837-88), embracing Darwinian pseudoscience, thought nothing of considering Venus as the abode of life;

It is clear that, merely in the greater proximity of Venus to the sun, there is little to render at least the large portion of her surface uninhabitable by such beings as exist upon our earth. This undoubtedly would render [the sun’s] heat almost unbearable in the equatorial regions of Venus, but in her temperate and subarctic regions a climate which we should find well suited to our requirements might very well exist … I can find no reason … for denying that she may be considered the abode of creatures as far advanced in the scale of creation as any which exist upon the earth.

Many of Denning’s contemporaries thought it a certainty that life exists on other planets. Today, many of us know better though.

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To be Continued in Part II

 

De Fideli

A Short Commentary on Percival Lowell’s “Mars as the Abode of Life.”

Adventurer in thought: Percival Lowell ( 1855-1916)

Adventurer in thought: Percival Lowell ( 1855-1916)

 

 

 

 

 

 

 

 

A work dedicated to Dr. Paul G. Abel

Biographical sketch: Percival Lawrence Lowell was born in Boston, Massachusetts on March 13 1855, the eldest son of Augustus and Katherine Bigelow Lowell. A ‘Patrician’ American family, the Lowells were financially successful and politically well-connected. Their wealth could be traced to the efforts of an ancestor, Francis Cabot Lowell, Perciival’s great great uncle, who, after visiting the mechanised textile mills of Lancashire, in Northern England, returned to the ‘colonies’ with his own ideas to establish a cotton mill at Waltham, MA. Such a venture was to dramatically change the fortunes of the family, propelling them to the top of the social order. Lowell’s father presided over his many business ventures with an iron fist, becoming widely known as a martinet in all that he set his mind to. Not content to let his children wallow in the prosperities accrued by earlier generations of the family, Augustus expected them to excel at whatever they set their mind to. And in this capacity they fulfilled that duty. Percival’s younger brother, Abbot Lawrence Lowell (1856-1943) became a distinguished educator and legal scholar, serving as President of Harvard University from 1909 to 1933. His much younger sister, Amy (1874-1925), became a well known poet and was posthumously awarded the prestigious Pulitzer Prize for Poetry in 1926. Percival himself was enrolled in various private schools at home and abroad, eventually attending Harvard, where he excelled at both English literature and mathematics, graduating with honours in 1876.

So proficient was Lowell at mathematics, that one of his professors, Benjamin Peirce, invited him to stay at the University to teach the subject, but he declined, later recalling that, “I preferred not to tie myself down …. not because mathematics had not appealed to me as the thing most worthy of thought in the world.” Adventurous and self-confident, the young, Bohemian Lowell took himself off to Europe on a year-long tour of its capital cities, venturing as far as Syria before returning home in 1877. For the next six years, he got stuck into his family’s cotton business, serving as it executive head for a short time. But such work proved far too mundane for Lowell to commit to and so, in 1883, he set off for Japan in search of new interests. This was the first of three trips to the Far East Lowell would embark upon over the next decade. Why he did this is still uncertain, but the young man was known to have cultivated quite an ego, so much so that it made it “almost impossible” for him to settle down in Boston.

There, far from home, Lowell would immerse himself in the alien culture of the yellow man, learning his languages and customs, but ultimately conceding that the peoples of the Orient had represented the survival of the unfittest, their ‘evolution’ having been prematurely stunted by their lack of imagination and the suppression of ‘individualism’ within their societies. Lowell’s opinions were strongly shaped by the pervading ideas of his day; social Darwinism. A nation was to be measured ultimately by its gross domestic product, competing with others, both economically and culturally, for a place at the top table. In a Universe infinitely old, with no God looking over his shoulders, it was the only brute reality that made sense to him. This was the world view that shaped his future career and which made him the man he became. Such ideas were set out squarely in his earlier literary works which included Choson: The Land of the Morning Calm, published in 1886, and the Soul of the Far East, which hit the bookshelves in 1888.

Lowell’s foray into telescopic astronomy began early, when his mother gifted him a fine 2.5 inch Clark refractor at the tender age of 16. From the opulence of his family mansion at Sevenels, Heath Street, Boston, he would observe the heavens. It was around this time also that his life-long interest in the planets was stoked. In the fertile playground of his imagination, Lowell believed that the celestial worlds beyond the Earth were places where, “our wildest fancies may be commonplace facts.” He likened the great observers of his day to Columbus of old, discovering and exploring brave new worlds. What better way to dedicate one’s life than to join in the search to uncover something of the culture of these civilizations in the sky, which had evolved completely independently of those on Earth.

One man in particular, embodied the spirit of this new age of exploration, the Italian astronomer, Giovanni Schiaparelli (1835-1910), who, during the Great Opposition of 1877, observed a dense network of linear structures through his telescope on the surface of Mars which he called “canali” in Italian, meaning “channels” but which became mistranslated into English as “canals”. His admiration for the Italian visionary comes into sharp focus in Lowell’s earlier work; Mars and its Canals (1906);

To Schiaparelli the republic of science owes a new and vast domain. His genius first detected those strange new markings on the Martian disk which have proved a portal to all that has since been seen…. He made there voyage after voyage, much as Columbus did on Earth, with even less of recognition from home.

With the news of Schiaparelli’s failing eyesight in the mid 1890s, Lowell took it upon himself to continue the work that he had begun. Lowell had acquired considerable experience with larger telescopes. Indeed, a 6-inch Clark achromatic had accompanied him whilst travelling to Japan.  But to carry out serious research on the Red Planet,Lowell began to look for larger instruments. His influence at Harvard allowed him to borrow a fine 12-inch Clark and he even convinced the trustees at Harvard College to enlist the services of the staff astronomers to scout out locations in the American southwest where the seeing conditions were  particularly  good for planetary observation. Eventually, Lowell decided to build an observatory at Flagstaff, Arizona, where he would carry out the majority of his observations of the planet Mars.

At a cost of $20,000 (over $500,000 in today’s currency), the main instrument chosen by Lowell was massive, fully 2 feet across (24 inches clear aperture) with a focal length of 30 feet (f/15), the optics housed in a tube fashioned from riveted steel. Lowell mounted two other instruments alongside the main telescope, also refractors of 12-inch and 6-inch aperture, either of which could have served as the centrepiece of a small college observatory in their own right. The telescope was placed on a massive clock-driven equatorial mount. The vaulted dome in which the great telescope was housed, was designed by an ex-cowboy-turned machinist, Godfrey Sykes, and was erected from hatchet-hewn ponderosa pine timber by a team of ten labourers in as many days!

The magnificent 24-inch Clark was the primary instrument used by Lowell to conduct his Martian studies and his observations formed the basis of his famous books on the subject of extraterrestrial life. Curiously, at a cost of $300,000 (provided by public donations and private benefactors), the historic telescope has recently (as of 2015) received a new lease of life to inspire future generations of star gazers (see the October 2015 issue of Astronomy Now for a interview I conducted with the staff at Lowell Observatory).

The newly refurbished 24-inch Clark refractor used by Percival owell to carry out his Martian observations. Image courtesy of Sarah Conant, Lowell Observatory.

The newly refurbished 24-inch Clark refractor used by Percival Lowell to carry out his Martian observations. Image courtesy of Sarah Conant, Lowell Observatory.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Another view of the restored 24-inch Clark at Lowell Observatory. Image courtesy of Kevin Schindler, Lowell Observatory.

Another view of the restored 24-inch Clark at Lowell Observatory. Image courtesy of Kevin Schindler, Lowell Observatory.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In 1908, at the age of 53, Lowell married Constance Savage Keith (1863-1954), eight years his younger. Well connected, Constance made her name and her money in the real estate business. Indeed, the couple were first acquainted when he bought a property from her. They honeymooned in London, taking a hot air balloon ride over Hyde Park in order that he could photograph the landscape. Quite possibly, Lowell was thinking of the Martian canals he had seen through his telescope and wanted something to compare them with.  Constance outlived her husband by nearly four decades, spending most of that time as a recluse before passing away at the ripe old age of 91.

Author’s Comments on the Preface: The trustees of the Observatory encouraged Professor Lowell to popularise his ideas about life on Mars through a series of public lectures, setting out, in a step-by-step manner, the scheme of events as he understood them, that shaped the evolution of the Red Planet.The lectures he conducted were an over-night success, mesmerizing his audiences with a sincere and compelling vision of how life arose on Mars and evolved through Darwinian means to create a race of intelligent beings fighting desperately to survive on a dying planet. People from all around the world flocked to hear the urbane astronomer deliver his sensational allegory. The book was a lucrative spin-off of these lectures and became an international bestseller. Then, as now, there was no shortage of people who were all too eager to surrender their sovereignty as supremely created beings, uniquely made in the image of God, throth’d to ‘the fountain of all life’, for a new kind of ‘reality’, dreamt-up and cultivated by ‘influential’ people, that of a plurality of habitable worlds at every conceivable stage of development; a Universe with infinite possibilities, a cosmos where Man could no longer be at the apex of the Natural Order. Never once did they consider a truly astonishing, and, as yet, unfalsified conjecture; that God created life uniquely on Earth and nowhere else as a personal revelation of His glory and love for us!

Chapter I: The Genesis of a World

In this opening chapter, Lowell recounts the cosmogeny of the Solar System, in which he imagined the Sun and its retinue of worlds being formed from gas and dust that had slowly coalesced under the auspices of gravity, heating up as they did. To Lowell, it was the property of mass itself that determined the evolutionary fate of the Sun and the planetary bodies, an idea that still holds currency with us today.

Lowell believed that the stuff of the heavens and of the Earth were one and the same. As evidence, he discusses the properties of meteorites – stony or metallic in character – in which some 26 of the same chemical elements were found to constitute them and not one that did not occur on Earth. To Lowell, this provided powerful evidence that whatever occurred on Earth must inevitably occur on other worlds, including Mars.

Lowell then presents six stages of planetary formation from “sun to cinder.” The size and mass of the body ultimately dictating whether it would remain in a primordial state or could evolve through various stages. These stages ( pp 12)  he identified as:

I The Sun stage: Hot enough to emit light

II. The Molten Stage, hot but lifeless.

III. The Solidifying Stage, where solid surfaces formed. Ocean basins determined. Age of metamorphic rocks.

IV. The Terraqueous Stage: Age of Sedimentary rocks.

V. The Terrestrial Stage: Oceans have disappeared.

VI The Dead Stage. Air has departed.

In this scheme, Professor Lowell considered the outermost planets; Jupiter, Saturn, Uranus and Neptune in the 2nd ‘planetological’ stage. The Earth was at Stage IV, Mars, V and the Moon at the sixth stage.

Note that Lowell took it ipso facto that the planets were not the same age. Jupiter, for example, was younger than the Earth, Mars older.

As one proceeds to read more of this chapter, one gets the distinct impression that Lowell was not so proficient with science as he was with mathematics. For example, he seems to have believed that the larger the planet the greater the height of its mountain ranges.

Now, when we come to scan Mars with nicety, we are gradually made aware of a curious condition of its surface. It proves singularly devoid of irregularity. The more minutely it is viewed, the more its levelness becomes apparent. (pp 16).

Smaller planets, of which Mars is in relation to the Earth, have weaker gravitational fields and thus might be expected to have taller mountain ranges and not smaller ones as Lowell surmised. For instance, we now know that great shield volcano, Olympus Mons, soars over 25 kilometres into the Martian sky – more than three times higher than Mount Everest. Indeed, Olympus Mons remains the largest volcano yet discovered in the Solar System.

Lowell believed Mars to be completely devoid of mountains (pp 17).

The remainder of the first chapter covers other aspects of planet evolution. Lowell firmly presents the idea that the internal heat of a planet will shape its future development. As a curious aside, he discusses the origin of the Moon and seeks to explain why its surface ended up so much rougher than the Earth. Lowell believed that the Earth and Moon were forged from the some matter and mentions the theory of the British astronomer, Sir George Henry Darwin (1845-1912), who believed the Moon spun off the Earth in the distant past, the two bodies having once been fused together in a pear-shaped mass which split into two bodies proper. Lowell uses this theory to explain how it ended up so battered and cratered. The internal heat of the primordial Moon i.e. vulcanism, was responsible for its vast crater fields and mountain ranges. When it lost its atmosphere, weathering all but ceased. There is no mention of impact-induced cratering.

Chapter II: The Evolution of Life

Covering pages 35-69

In this section of the book, Lowell pronounces his faith in Darwinian evolution. Eschewing his Christian heritage, Lowell found in Darwinism a way to explain the origin and development of life through its various stages. Lowell discusses the fossil record – as wholly incomplete as it was then – to espouse his idea that when the necessary chemical conditions are met, life was an inevitability, as sure of emerging as rocks and minerals.

I shall not dwell on a criticism of Lowell’s ideologies about how life came into being, either on Earth or on Mars, only to state a few simple points that cast righteous doubt on the validity of his ideas.

  1. Scientists were gloriously unaware just how complex even the simplest forms of cellular life were during the late 19th century and early 20th centuries. Had Lowell been able to see the astonishing internal organisation of the cell as revealed by techniques such as electron microscopy and X-ray crystallography, a simple appeal to probability would surely have cast a long shadow of doubt in his mind. On the contrary, Lowell, like Darwin, thought the cell to be merely composed of blobs of protoplasm – much like a warm, gelatinous soup of salts and amino acids – that was not very complex and thus might have easily arisen by purely naturalistic means.
  2.  The fossil record was very incomplete in Lowell’s day but he nonetheless took a leap of faith in accepting it. Today, although some leading evolutionary biologists are engaged in a kind of aggressive denial that Darwinian ideas are wrong, the truth is that the fossil record falls far short of supporting any Darwinian scenario, which anticipated innumerable transitional forms. Indeed, it could be argued that the best explanation for the fossil record are waves of creation events, replacing one strata of life with another to better cope with the changing conditions on our planet over the aeons. The Ediacaran and Cambrian radiations provide rock-solid evidence for a creationist perspective.
  3. Great advances in knowledge have cast even more doubt on the evolutionary paradigm as promulgated by contemporary biologists. This author has spent much time summarising the many intractable problems with the theory.
  4.  In one recent analysis, this author has clearly and unambiguously shown that even the simplest steps towards the creation of living systems requires an inordinate amount of intelligent design; so much so that a wholly naturalistic emergence of a living system is scientifically untenable.

 

Chapter III The Sun Dominant

Covering pages 70-110

In this chapter Lowell sets forth his understanding of how the progress of planetary evolution transitions from one that is dependent upon its own intrinsic heat to that of the energy provided by the Sun. In very elegant and engaging prose, Professor Lowell develops the idea that in the earliest ages of rocky planet evolution, lifeforms rely almost entirely on the energy resources of the planet, but slowly, over the ages, the atmosphere of the planet clears, transitioning from dark and murky to clear and transparent. Lowell finds evidence for such a scheme of events in the various strata of the then known fossil record. As our own planet allowed more and more light to penetrate to the surface, so too did it evolve ever more sophisticated plant life to take advantage of this steadily increasing solar irradiance.

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Author’s note: Today we understand that the Sun has steadily brightened over the aeons, being between 10 and 15 per cent less luminous at its inception than it is presently. This was unknown to Lowell and his contemporaries. Moreover, this brightening will continue apace until life on Earth will no longer be possible. We thus find ourselves in a fortuitous ‘window’ of time where our technical civilization can flourish on a global scale, supporting a human population – sons and daughters of God – far larger than has ever been possible. We live at the best possible time and in the best possible place, in the entire history of the cosmos.This was part of the Divine Plan, pledged before the foundation of the world. See Genesis 17:6

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Lowell then applies the same ideas to the planet Mars, Earth’s elder brother, and notes that the process of atmospheric clearing has progressed more than on Earth, its air being almost devoid of clouds. It is in this chapter that we get our first description of the telescopic appearance of the Red Planet as seen through the great telescope used with diligence by Lowell:

Viewed under suitable conditions, few sights can compare for instant beauty and growing grandeur with Mars as presented by the telescope. Framed in the blue of space, there floats before the observer’s gaze a seeming miniature of his own Earth, yet changed by translation to the sky. With its charmed circle of light, he marks apparent continents and seas, now ramifying into one another, now stretching into unique expanse over wide tracts of disk, and capped at their poles by dazzling ovals of white. It recalls to him his first lessons in geography, where the earth was shown him set ethereally amid the stars only with an added sense of reality in the apotheosis. It is the thing itself, stamped with that all-pervading, indefinable hall-mark of authenticity in which the cleverest reproduction somehow fails.

pp 73-74.

The reader will note that Lowell describes the achromatic Martian images as having an ‘instant beauty’. And yet, the great Clark refractor employed by Lowell had a significant amount of chromatic aberration.

Lowell continues this chapter by discussing some of the features of the Martian environment. It’s tilt is similar to that of the Earth and its year, nearly twice as long. Thus, Lowell concludes, it will experience similar seasons to our own world, only longer in duration.Telescopic investigation correctly revealed that Mars has a thin atmosphere as deduced by the presence of morning and evening mists observed on the planet’s limbs, and, like the Earth, has prominent polar caps. There was still some debate about whether these ice caps were composed of water or , as others had suggested, carbonic acid (this is essentially an aqueous solution of carbon dioxide), but Lowell seems to favour the water ice hypothesis. His reasoning is this: carbon dioxide would sublimate at the temperatures and low pressures on the Martian surface and thus would not produce a liquid. On the contrary, he brings to our attention a dark rim that is seen girdling the ice cap as it ‘melts’ in late Spring and throughout the Summer. Presumably, the snow melt would darken the terrain immediately around the ice cap.

After discussing the albedo of Mars (he provides a value of 0.27) and the other planets, Lowell then addresses the question of the planet’s surface temperature. Though it is not entirely clear how he comes up with these figures, he seems to accept a mean surface temperature of 48 degrees F (9C). That being said, Lowell seems to be under the impression that, owing to the greater length of the Martian seasons, it will enjoy greater temperature swings (up to 50 degrees F) during the summer months, despite its thinner atmosphere. In essence, he treats Mar’s environment much like the deserts of Earth, heating up rapidly as the Sun rises higher in the Martian sky and cooling off rapidly (to sub-zero temperatures < 32 degrees F) as it sinks below the horizon at the approach of night.

Here at least, the essence of Lowell’s deductions are sound. The temperatures can indeed rise as high as 20C (68F) within a few inches of the surface, near the equator, during the height of a Martian summer but its mean global temperature is nearer -60F, far lower than Lowell was willing to entertain.

pp74-81

Here Lowell provides the observational evidence that Mars, at least superficially, has many gross features in common with the Earth. The careful student of the Red Planet will notice features; a dark marking, a bright spot or some such, traversing the disk, disappearing behind one limb and reappearing some time later on the opposite side of the planet. Such observations naturally led to the idea that the planet is rotating. Furthermore, Lowell informs us that the length of the Martian day (or ‘Sol’) is only a little longer than our own; 24 hours and 40 minutes. Furthermore, the angle of the planet’s tilt turns out to be ‘singularly’ like our own; 24 degrees as opposed to 23.5 degrees for our planet. This, together with the planet’s longer year, would naturally translate into commensurately longer seasons, with spring lasting 199 days, summer 183 days, autumn and winter 147 and 158 days, respectively.

Lowell’s magnificent telescope also provided him evidence of a thin but substantive atmosphere enveloping the planet, as inferred by the presence of clouds and mists that accumulate on the planet’s morning limb and various other refractive phenomenon that could be best explained had Mars been endowed with a sea of air. His fecund imagination carries us to the Martian surface, where he draws our minds’ eye to a Martian dawn or dusk. Because of the thinness of the the planet’s air in comparison with the Earth, Lowell conjectures correctly that twilight would be very brief affair in comparison with the Earth. Day and night would come more abruptly on this neighbouring world, and with little forewarning, the stars shining with a brilliance and steadiness(owing to the rarefaction of the atmosphere) quite unlike anything seen on terra firma.

pp 81-85

In this section, Professor Lowell once again puts forth his reasoning on the nature of the intensely white polar ice caps clearly on view through his telescope. Lowell saw a darkened ring called ‘blue belt’ encircling the polar cap and seems to have been ‘confirmed’  by a number of other observers:

The blue belt proclaimed the presence of a liquid. Thus carbonic acid could not be concerned, and the substance composing the caps was therefore snow. For no other, that we know of, dons their snowy aspect with change of state.

pp 82.

Today we know that the Martian ice caps are indeed comprised mostly of water ice, with a thin (~1 metre thick) veneer of carbon dioxide ice dusting their uppermost parts. What is more, as autumn marches into winter, the growing ice cap sequesters some 20-30 per cent of the Martian atmosphere (mostly carbon dioxide), drastically reducing the atmospheric pressure on the planet by the same amount.

pp 85-90

In these pages, Lowell explores the thorny question of what kinds of temperatures are enjoyed by Mars as it orbits the Sun. The Martian orbit is noticeably more eccentric than the Earth’s (0.0934 as opposed to just 0.0167 for our planet), varying from 1.67 A.U. at aphelion to 1.38 A.U at perihelion passage, causing the planet’s solar irradiance to vary from approximately 1.9 and 2..8 times lower than those enjoyed on the Earth’s surface. This greater eccentricity would render the Martian seasons more erratic than those on Earth. The Red planet is at its closest when its southern hemisphere is tilted towards the Sun. So the southern hemisphere experiences hotter summers than the northern hemisphere.

Lowell clearly understands that this is a complex question with many factors having to be taken into account, including the albedo of the planet, the thinness of the atmosphere and its chemical constitution etc. Lowell holds onto one over-arching fact that illuminates his entire thought process; on Earth, owing to the presence of substantial cloud cover, the sky is such that the Sun shines only half the time it might were there no clouds to screen it. On Mars, where the skies are innocent of cloud cover, the Sun can warm the surface more effectively. Indeed, on page 86 Lowell suggests that when everything is taken into account, the average surface temperature was 48 degrees Fahrenheit as opposed to 60F on Earth (8.9 C and 15.5C, respectively).

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Author’s note: There is considerable repetition of ideas in this chapter, particularly on the subject of the Martian polar caps. Lowell was certainly preoccupied with driving home the idea that Mars had water ice- which it certainly has – and that its atmosphere could stably sustain liquid water. One can only surmise that Lowell may have viewed these points as being crucial to the undergirding of his ultimate conclusions.

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So, according to Lowell, Mars was a cold planet, but not nearly so cold as to preclude the possibility of life having taken hold upon it.

pp 95-106

This is especially the case, since global average temperatures don’t really reflect the temperatures encountered at various latitudes and at various times of the Martian year, where increases in heat and cold may be encountered. Lowell explains that because of the long Martian summer, temperatures continue to rise owing to the planet’s ability to absorb more heat than it reflects back into space.  He was clearly convinced that during these clement periods that temperatures would soar so much that it would permit animal and vegetable life to prosper and reproduce. Indeed, Lowell goes out of his way to stress that it is the mean summer temperatures and not that of the winter that would dictate the kinds of habitat likely to be encountered on the planet’s surface.

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Author’s note: Spacecraft that have landed successfully on Mars have shown that  soil temperatures can reach a very comfortable 20C during the heat of a Martian summer at the equator but can fall as low as  -153C at the Martian poles. The mean Martian temperature is much lower than what Lowell imagined though – somewhere in the region of -60C. This is far more harsh than Lowell was ever able to entertain.

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Lowell then presents the best terrestrial analogy of life in a thin Martian atmosphere by discussing at length the plight of living things who have eked out a living at higher altitude on Earth, where the atmospheric pressure falls away exponentially. In particular, he discusses the mountains of California, at altitudes up to 12,600 feet, where hardy coniferous trees seem to live happily. Lowell argues that since life has adapted well to the thin mountain air, so must the animal and vegetable life on Mars.

pp 106-110

In this, the concluding part of this chapter, Professor Lowell launches into his classic evolutionary train of thought; if there exists the necessary conditions to allow life to flourish on the Red Planet, then time is the necessary ingredient for evolution to take place, starting with the simplest forms of life and ascending upward towards ever more complex animals, and finally the emergence of intelligence and self awareness. Lowell correctly asserts that while his telescopic observations could never hope to reveal the bodily forms directly, intelligent beings, through the gradual control of their environments, would inevitably build larger and larger artificial structures. Then and only then, could they betray their presence to an Earth-bound telescopist:

Subjugation carries its telltale in its train, for it alters the face of its habitat to its own end. Already man has begun to leave his mark on this his globe, in deforestation, canalization, in communication. So far his town and his tillage are more partial than complete. But the time is coming when the earth will bear his imprint and his alone. What he chooses will survive; what he pleases will lapse, and the landscape itself become the carved object of his handi-work.

pp 109-110.

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Author’s note: Despite what paleoanthropologists wish to promulgate through their myopic belief in the evolutionary paradigm, there is no hard evidence that human beings evolved from lower animals. Determined to make their case and shore up their world view, these scientists deliberately ‘project’ their own images onto these fossils, which are invariably incomplete skeletons, in order to present them in as human-like a way as possible.  But this is little better than the fraudulent drawings made by 19th biologists such as Ernst Haeckel, who attempted to show that many animals begin development in essentially the same form. What paleontologists engage in today is just more sophisticated ‘bluffery’ of essentially the same nature as Herr Haeckel’s analysis.

And while there undoubtedly existed hominins which lived for a short time before going extinct, none of these animals left any signs that they had cognitive and behavioural capacities any more advanced than the Great Apes we share our planet with today. The Bible clearly professes that Man was a special creation, made in the image and likeness of God (the Imago Dei):

And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.

Genesis 2:7

Even the most ‘advanced’ hominin to have been uncovered by paleoanthropologists, the Neanderthals, left no artefacts that would comport to modern human behaviour. And despite some evidence that traces of Neanderthal DNA can be recovered from some human gene pools, this could as well be explained by an ancient act of bestiality than anything else. Why else would the Lord warn us in His Levitical statutes?

Neither shalt thou lie with any beast to defile thyself therewith: neither shall any woman stand before a beast to lie down thereto: it is confusion.

Leviticus 18:23

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Chapter IV Mars and the Future of the Earth

pp 110-120

In this chapter Professor Lowell advances his theory that Mars presents a glimpse of what the Earth will look like in the distant future. But he also believed the converse was true; that in the distant past Mars had oceans of liquid water just like our world but had managed to lose much of it over the aeons. The mechanisms driving the loss of this water to interplanetary space, according to Lowell, are the result of Mar’s weaker gravitational field, which would allow a small molecule like water to attain the escape velocity of the planet ( which is only about 45 per cent of that on Earth i.e. ~11 km per second). This is a plausible scheme of events. One significant mechanism for water loss involves photolysis, that is, the chemical breakdown of water by high energy solar radiation at high altitude, releasing oxygen and hydrogen. The latter being very light and sprightly, would easily escape into space, whereas the heavier oxygen, being highly reactive, would be sequestered by  surface minerals, slowly oxidising them over time.

Lowell suggests that water loss has also being going on here on Earth over the aeons and cites some evidence from the best available geologic evidence available to him at the time.

Lowell’s drawings of Mars in this section ever more boldly show the presence of curious linear features – the fabled canals – criss-crossing the planet.

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Author’s note:

Today scientists have painted a much more complex picture of how Earth acquired and maintained its oceans. While it is certainly possible for water molecules to acquire enough kinetic energy to escape the gravitational field of the Earth, we now know that it can be replaced by water issuing from the Earth’s interior, so that the net result is that our planet has maintained its substantial water oceans over billions of years. Indeed, while most of us consider the Earth to be a water rich world, the reality is that it is substantially the very opposite; the Earth is water poor. Only a thin veneer of water covers our world and in terms of mass, constitutes just a small fraction of one percent of the planet’s total mass. Indeed, the Earth’s neonatal water inventory was much higher, which would have led to the formation of a perilously deep global ocean, so much so that it would likely not have enabled landmasses to emerge above the surface. Without landmasses, there would be no facility to efficiently recycle nutrients to sustain the complex biosphere our world would come to nurture. Had a Mars sized object not collided  with the primordial Earth, our planet would have likely ended up with a chokingly dense atmosphere and far too much water to allow complex life to flourish. In this sense, NASA’s mantra, “follow the water,” is  too simplistic and misleading, as far more factors must be set in place before a planet can sustain life. Future surveys of extra-solar planets will likely confirm this in the coming years. Having water does not equate with having life.

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pp 120-130

In this section of the chapter Professor Lowell discusses the phenomenon of desertification, of which, in this capacity, elder brother Mars was in a far more advanced state. Slowly but surely, this increasing aridity will eventually cause our planet’s lakes and seas to disappear. Lowell uses many reasonable arguments to drive home his point, discussing the petrified trees and forests of Arizona, and going further afield to the ancient city of Carthage in North Africa, Egypt and Palestine, where clear evidence for dried up rivers exist. The great engineering feats of the Romans – the aqueducts especially – are also used by Lowell to impress the point that while plentiful water once flowed for hundreds of miles through these ingenious constructions, the water has now largely disappeared. In this way, Lowell asserts that all civilizations eventually will build systems of irrigation, channels, canals, aqueducts to allow their peoples to flourish in regions that would otherwise be quickly reclaimed by the deserts.

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Author’s note:

Lowell was indeed correct to claim that the process of desertification is increasing on Earth. Today we know that each year an area roughly the size of Ireland is reclaimed by the advance of the deserts, especially when one looks at the huge increases in the area of the Sahara (which has expanded some 10 fold in just two millennia) and Gobi ( three times larger) deserts in particular. But while Lowell claims that there is a definite sense of inevitability about the onward march of the deserts, it does not mean that it can’t be stemmed or even reversed. In arguably the oldest book of the Bible – Job – chapter 38 – the Lord speaks about precipitation and the water cycle at some length;

Who hath divided a watercourse for the overflowing of waters, or a way for the lightning of thunder;

To cause it to rain on the earth, where no man is; on the wilderness, wherein there is no man;

To satisfy the desolate and waste ground; and to cause the bud of the tender herb to spring forth?

 Hath the rain a father? or who hath begotten the drops of dew?

 Out of whose womb came the ice? and the hoary frost of heaven, who hath gendered it?

Job 38:25-29

Here we see the triune creator of the Universe sending water to places where no man lives, nourishing the wild plants that eke out a living there. And no flower blossom is truly wasted on the desert air! What seems clear from this passage is that in order to reclaim regions of the desert, we have a responsibility to first repair the damage we have wrought on these places. Humans are the principal culprits in the production of this new desert land, caused by over-grazing of their herds at the desert boundaries, stripping away the most nourishing grasses that grow there and using the remaining vegetation as cooking fuel. Yet, new scientific evidence suggests that if these regions bordering the great deserts are replanted, they not only curb the encroach of the parching sands but also encourage greater levels of precipitation, eventually reversing the march of desert land proper. Such initiatives would also absorb significant quantities of greenhouse gases like carbon dioxide, which in turn would cause the ancient cycles of precipitation to return. The process of transpiration in flowering plants contributes an astonishing 10 per cent of the Earth’s atmospheric water inventory and thus also would help cool these regions so that they can better sustain human and animal life. The Israelis have been world leaders in this initiative for decades and have managed to grow an incredible amount of food and other vegetable matter, which has made them the envy of their neighbours. Thus, the Lord has given us the ingenuity to keep this planet habitable for as long as He sees fit. Only by paying closer attention to God’s superior wisdom can we become better stewards of this wonderful planet we inhabit. Managed replanting would turn the Gobi and the Sahara into the bread baskets of the world. More on desert greening technology here.

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pp 130-140

In this section of the chapter, Professor Lowell discusses the ‘evidence’ for water and vegetation on Mars. He believes that the vast tracts of the planet that remain “opaline” in tint throughout a Martian year must be totally devoid of life, like one vast Martian Sahara, whereas the blue green areas he identifies with vegetation. His telescopic studies indicate that these tracts of vegetation occur at temperate latitudes and seem to grow in intensity and size as the planet transitions from winter through spring and then summer.

Lowell’s assistant, the young Vesto M. Slipher, attached a spectroscope to the great 24-inch refractor and captured spectra through red filters of the Moon and then Mars at the same altitude in search of the spectral signature of water vapour. In an inset sandwiched between page 138 and 139, Lowell shows the results of such spectra and identifies the ” a” line of water vapour in the spectrographs obtained from Mars but not from the Moon.

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Author’s note: Many astronomers active at the time were sceptical that Mars showed spectroscopic evidence of water vapour as the so-called  ‘a’ line captured by Slipher’s efforts was exceedingly weak. Between 1925 and 1943, astronomers, Walter Adam and Theodore Dunham of Mount Wilson Observatory, using much more sensitive equipment than that employed at Lowell Observatory, tried to detect oxygen and water vapour in the Martian atmosphere but their results were generally negative, or at best, ambiguous. Indeed, it was not until 1947 that the Dutch-American astronomer, Gerard P. Kuiper, obtained unequivocal evidence for carbon dioxide in the Martian air. Finally, using data obtained by the much more powerful 100-inch reflector atop Mount Wilson, astronomers Spinrad, Münch and Kaplan, finally detected traces of water vapour at 8200 Angstroms (820nm), and which were most strongly exhibited over the planet’s polar caps.  Reference here.

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pp 140-45

In these concluding pages Lowell sums up his thoughts on the state of affairs on Mars. He estimates that the total water inventory on the planet is 189,000 times less than that of the Earth. And yet, all the while, Lowell turns this bleak fact into an opportunity. For while Mars’ oceans of water have long disappeared, together with the all the marine life it must surely have harboured, evolution would have allowed for the development of advanced land-based creatures whose minds became ever more sharply focused on rendering this water supply accessible:

The evidence of observation thus bears out what me might suspect for the planet’s smaller size; that it is much further along its planetary career than is our earth. This aging in its own condition must have its effect upon any life it may previously have brought forth. That life at the present moment would be likely to be of a high order. For whatever its actual age, any life now existent on Mars must be in the land stage of its development, on the whole a much higher one than the marine. But, more than this, it should probably have gone much farther if it exist at all, for in its evolving of terra firma, Mars has far outstripped the earth.

pp 142-143

Using this line of reasoning, Lowell felt that some creature would have come to dominate all other forms of land life on the planet and through intelligence, would have pressed into service ‘brain over brawn’ in constructing artificial structures that would betray their presence across the sea of interplanetary space.

The stage is now set for Lowell to present the case for such structures and he finds his champion in a hitherto obscure Italian astronomer, Giovanni Schiaparelli (1835-1910).

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Author’s note:

index

The ongoing data obtained from the Kepler planet-finding mission has established that the Universe contains countless trillions of Earth-sized planets. A fraction of these will be located in the so-called habitable zones of their parent stars. But numbers alone are not enough to prove the link between the Principle of Plenitude and the Copernican Principle, as it might apply to life in the wider Universe. Does the age of a planet really relate to how habitable it can be?  Systems significantly older than the Earth might not have acquired the necessary elemental constitution to allow them to remain geologically active over a long enough time period to recycle minerals. For example, there is good evidence that the Earth is unusually enriched in long-lived radionuclides to sustain plate tectonic activity over its long history. This appears to have been a product of sheer serendipity and which could hardly have been foreseen by planetary scientists. The vast majority of these so-called habitable exoplanets will be much older than the Earth (8-8.4 billion years old) and some quirk of nature – of which there must be legion –  either dynamical or physio-chemical in nature, would likely scupper any chances of life gaining a foothold upon them. Curiously, there are signs that astrobiologists are coming round to recognising that these problems are real. See here for more details.

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Chapter V: The Canals and the Oases of Mars

The fabled Martian canals as drawn by Lowell.

The fabled Martian canals as drawn by Lowell.

Covering pages 146 to 183.

As we have previously seen, the Italian astronomer, G.V. Schiaparelli came to the world’s attention by claiming to have detected long, linear structures criss-crossing the Martian surface in 1877. Lowell attributes their relatively recent ‘discovery’ to the advancements in telescope optics. Schiaparelli used a fine 8-inch Merz achromatic refractor to detect the “canali,” which translates from the Italian as “channels.” Although Schiaparelli was initially cautious about ascribing an artificial origin to these linear features, he soon spoke out in favour of their ’artificiality’, especially after Lowell began to sensationalise their presence in his voluminous writings. Indeed, he doesn’t take long in introducing the word ‘canal’ in this chapter, appearing first on page 149. Curiously, he aims to drive home the artificial nature of these structures by providing the reader with aerial photographs (displayed on page 148) of real canals taken over the Serpentine recreational lake in Hyde Park, London, when he made a balloon ride during his honeymoon in 1908. These structures were created back in 1730 at the behest of the Queen Caroline. Lowell describes the appearance of the Martian canals;

…..the canals are of various length. Some are not above 250 miles long, while others stretch 2500 miles from end to end. Nor is this span by any means the limit. The Eumenides-Orcus runs 3450 from where it leaves the Phoenix Lake to where it enters the Trivium Charontis. Enormous as these distances are for lines which remain straight throughout, they become more surprising when we consider the size of the planet on which they are formed. For Mars is only 4220 miles through, while the Earth is 7919. So that a canal 3450 miles long, for all its unswervingness to right or left, actually curves in its own plane through an arc of some 90 degrees round the planet. It is much as if a straight line joined London to Denver, or Boston to Bering Strait.

PP 149-150.

Schiaparelli himself detected 113 canals and Lowell increased the tally to 437 at Flagstaff. To the untrained eye, these canals seemed rather haphazard but Lowell insisted they had a “regular irregularity”:

It resembles lace-tracery of an elaborate and elegant pattern, woven as whole over the disk, veiling the planet’s face. By this means the surface of the planet is divided into a great number of polygons, the aerolas of Mars.

pp 151

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Author’s note: It will be of interest to the reader that Schiaparelli also believed in Darwinian evolution and was himself a hydraulic engineer by training. Combining his world view with his profession, he arrived at the perfect synthesis of both: vast canal structures designed by advanced Martian engineers.

The canals were also ‘seen’ by astronomers using silver-on-glass reflectors. The great British student of Jupiter, Arthur Stanley Williams (1861-1938), reputedly saw some of them with a 6.5-inch equatorially mounted Newtonian, though he later sided with Eugene M. Antoniadi, that they were largely illusory.

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Over the next several pages, Lowell elaborates on what he and his assistants at Flagstaff had discovered about the canals. Many of them seemed to converge on dark spots, which W.H. Pickering dubbed ‘lakes.’ Lowell, in his ‘Lawrence of Arabia’ mindset prefers the term, ‘oases,’ 186 of them in all, claiming that many canals converge at these points;

In the case of one of them, Ascraeus Lucus, no less than 17 canals converge to it.

pp 157.

And then, Lowell explains that while many of these canals are singular in nature, some appeared duplicitous under telescopic study:

Out of the 437 canals so far discovered, only 51 have ever shown duplicity.

pp 159

He ‘justifies’ the reality of their duality by asserting that if these were the product of some optical aberration, all of the canals would appear likewise.

On page 162, Lowell discloses the distribution of the recorded canals as a function of Martian latitude. The vast majority appear to be concentrated within a few tens of degrees of the equator, both north and south.

Over the next 12 pages or so, Professor Lowell introduces new and more elaborate terminology. Plotting the appearance of the canals as a function of Martian date and latitude, he came up with diagrams ( one illustrated on page 174), which he referred to as “cartouches”. Furthermore, these “cartouches” participated with the “waves of darkening” in an elaborate  interplay between the available water distribution and Martian vegetation.

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Author’s note: Lowell is clearly attempting to drive home his belief that the Martians were using their canal networks to optimise agriculture. It is interesting that Lowell introduces Egyptian symbolism (pp 171) in his analysis; a common feature of mystery religion literature.

It has recently been discovered that the Martian soil is rich in highly toxic substances known as perchlorates, which, at the concentrations detected on the Red Planet, would likely prove toxic to any would-be photosynthetic organisms. The ubiquitous levels of perchlorate on Mars would severely scupper any attempts by future colonists to grow crops for human consumption. Martian soils are also nitrogen-poor (content is below the minimum measurable level. i.e <0.1%) in comparison to those on Earth; source.

Mars, like everywhere else outside the Earth, is a hostile place for life.

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Chapter VI: Proofs of Life on Mars

Covering pages 184-216

In this, the final chapter, Lowell doesn’t really break much new ground, beyond more wild speculations concerning the morphology of the illusory canals. Rather, he goes over old ground, re-stating and summarising material discussed in previous chapters in order to consolidate the points he wishes to stress. Further to this he maintains that, owing to the advanced evolution of Mars beyond that of the Earth, the indigenous life too is nearing its end. Lowell restates his cosmogony about life, the Universe and everything on page 215-216:

Thus, not only do the observations we have scanned lead us to the conclusion that Mars at this moment is inhabitable, but they land us at the further one that these denizens are of an order whose acquaintance was worth the making. Whether we ever shall come to converse with them in any more instant way is a question upon which science at present has no data to decide. More important to us is the fact that they exist, made all the more interesting by their precedence of using the path of evolution. Their presence certainly ousts us from any unique or self-centred position in the solar system, but so with the world did the Copernican system the Ptolemaic, and the world survived this deposing change. So may man. To all who have a cosmoplanetary breadth of view it cannot but be pregnant to contemplate extra-mundane life and to realize that we have warrant for believing that such life inhabits the planet Mars.

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Author’s note:

Lowell died a century ago this year, and it is no exaggeration that his legacy has had a profound effect on the scientific attitudes of the next generation of scientists. Lowell wanted us to dream; to rise above the ‘mundanity’ of this existence and to contemplate another more encompassing cosmology where our perceived ‘importance’ was merely an illusion. We are citizens of the cosmos and not just the Earth. Lowell’s writings inspired a whole genre of science fiction, including the most famous of all; The War of the World’s by H.G. Wells. It is because of Lowell that we send robotic emissaries to the Red Planet every other year, exploring its wonderful mysteries from the ground and from orbit. He has given us wings!

The Martians of Lowell’s imaginations do not exist however. And while probes continue to look for signs of life on Mars, it appears as though it’s a very hostile place. But we cannot yet say for sure whether it is completely devoid of life. There may exist microbial ecosystems living deep underground, protected from the harsh radiation incident on the planet’s surface. Traces of methane have been detected on the surface, but it is not yet clear whether this is a geological source or the manifestation of active microbial activity. We shall know which of these scenarios (or even both) are valid in the near future, God willing. Knowing that the Earth has been richly filled with living things over billions of years, it is almost certainly the case that some of this life will have made its way to Mars, given its relative proximity to the Earth.  Whether that life is extant or not is another question entirely though. Given the harshness of the Martian environment, the probability is low, but still finite.  With the entrenched presumption of a non-supernatural explanation for life’s origins, many scientists will be eager to ascribe such a finding to indigenous  Martian life, having independently arisen there.  Future missions should develop diagnostic techniques to distinguish  between these two possibilities. Further afield, there is a slim but non-zero chance that Earth life might have seeded other solar system bodies over the aeons.

Many scientists anticipate that life will be common place in the galaxy, but this is based on Darwinian reasoning. However, there are many legitimate reasons to doubt the Darwinian paradigm, not least of which are the compelling probability arguments now being developed by scientists advocating intelligent design. What is certain is that Darwinian evolution will not survive the information age that is now upon us. Furthermore, though not conclusive, the lack of success of detecting extra-terrestrial intelligence provides further evidence that the Darwinian paradigm is not likely to be valid in the wider Universe, so we should not expect them to chime in any time soon (if at all).

The exploration of Mars and other solar system bodies is a worthwhile scientific venture, but the extreme risks that attend manned missions, together with its enormous cost to the tax payer are good reasons to continue robotic missions to the planets. And as for colonisation, it is much easier to maintain the viability of our precious world before ‘abandoning ship’, as it were, and looking to others. We owe this much to the Earth.

Additional Reading: Rovers Report on Mars’s Past Potential Habitability

Further Viewing: An Introduction to Information Theory

Lecture 1

Lecture 2

Lecture 3

Lecture 4

Lecture 5

Lecture 6

Lecture 7

Lecture 8

Lecture 9

Lecture 10

Lecture 11

Lecture 12

Lecture 13

Lecture 14

Lecture 15

Lecture 16

 

De Fideli

 

 

 

Tales from the Golden Age: The Life & Work of William Frederick Denning (1848-1931).

William Denning ( 1848-1931) pictured with his With-Browning reflector on its simple altazimuth mount.

William Denning (1848-1931) pictured with his 10-inch With-Browning reflector on its simple alt-azimuth mount.

 

 

 

 

 

 

 

 

 

 

Remember the days of old, consider the years of many generations: ask thy father, and he will shew thee; thy elders, and they will tell thee.
Deuteronomy 32:7

W.F Denning Faciebat

 

Oh Spring! Dear Spring! Thou more must bring

Than birds, or bees, or flowers-

The good old times, the holy prime

Of Easter’s solemn hours:

Prayers offer’d up and anthems sung

Beneath the old church towers.

                                                                                                      W.F Denning

 

The mid to late 19th century was a period of frenetic astronomical activity in Britain. Inspired by the enthusiasm of home grown ‘clerical’ popularisers of astronomy, such as W.R Dawes and T.W Webb, a new generation of amateur astronomers, forming societies across the length and breadth of the country, would take up the gauntlet of observing the heavens in search of booty. Telescopes were becoming more popular, not just the achromatic refractor, which held a special place in the history of Victorian astronomy, but also the Newtonian reflector, which was experiencing a bit of a Renaissance owing to the introduction of silver-on glass mirrors offering decent aperture at prices that suited the budgets of many more amateurs. It was in this renewed spirit of enthusiasm that William F. Denning was to make his mark on the astronomical community.

Little is known of his early life. The eldest son of Lydia and Isaac Denning, William was born on November 25, 1848 in the picturesque village of Redpost, Somerset. Isaac was a retired army officer-turned-accountant, who provided a modest income for his family. When William was seven, the Denning family moved to the city of Bristol, presumably to realise a higher standard of living by entering an accountancy partnership – Denning, Smith & Co – where they prospered, and were further blessed by three more children – a brother Frederick and twin sisters, Margaret and Emma. Not much is known of William’s education, although judging by the standards of his many later astronomical correspondences, it is reasonable to assume that he received a good foundation at school. After leaving formal education, William followed his father into the accountancy business, remaining with the firm until Isaac’s death in 1884. William showed great promise as an athlete, cricketer and even dabbled in hockey. Indeed, according to a later account by T.E.R Philips, Denning was invited by the legendary cricketer, Dr. William G. Grace, to be a wicket keeper for the county of Gloucestershire – a considerable honour in itself – although for reasons that still remain obscure, he declined the offer. One guess is that the young man had other ambitions related to astronomy, which he had expressed an interest in as early as 1865, aged just 17.

One event that may have consolidated his decision to follow an astronomical career was the great Leonid meteor showers that occurred between 1866 and 1868, during which time many spectacular fireballs were witnessed streaming across the mid-November night sky, and having opened a correspondence with Alexander S. Herschel, the son of Sir John Herschel, who had carried out pioneering work on meteor spectroscopy. And while meteor watching was to become the enduring passion of Denning’s later life, his earliest forays into the hobby were decidedly varied. In 1865, Denning bought his first telescope, a good 4.5 inch refractor, with which he would carry out extensive work on the groupings of sunspots, observations of the transit of Mercury in the year 1868, as well as transit timings of the Galilean satellites of Jupiter, the latter of which formed the basis of his first publication, aged just 20, appearing in the Astronomical Register 6, Vol 92, 1868, and auguring his subsequent meteoric rise in the community of British amateur astronomers.

This first publication in the Astronomical Register was immediately followed up by several others in the next few years, during which time Denning was to spear-head a coordinated effort among dozens of his fellow amateurs to observe the Sun for a month-long period between March 14 and April 14 1869, in order to search for the elusive planet Vulcan, which was postulated to exist inside the orbit of Mercury. Although no such planet was ever seen, it did not in any way diminish his enthusiasm for coordinating multi-observer surveys in the future. Indeed, it was this boyish enthusiasm for his work that led to him founding a new society with the help of his more influential astronomical friends. Known as the Observational Astronomical Society (OAS), it was established on July 1 1869, with Denning himself acting as its first treasurer and secretary. Although the OAS did not ultimately have the legs to endure the sweeping changes that occurred over the coming years, ceasing altogether to exist after 1872, many would agree that it was a legitimate foreshadowing of the much more successful British Astronomical Association(BAA), which was founded in 1890, and which is still going strong today.

Intrigued by the growing interest in large aperture silver-on-glass reflectors that were the talk of the town during these years, and sensing ‘the pomp and ceremony’ of refractor culture, Denning used his brain and took a punt on a 10-inch f/7 With-Browning reflector with a simple alt-azimuth mounting, which he purchased in 1871. Being unusually enthusiastic about exploring the telescope’s potential under the starry heavens, the truth soon set him free, and he embraced the same instrument to embark on an extraordinary program of visual work on the bright planets. It was these observations, and his subsequent commentaries, that were to abruptly hurl the young man into the limelight of the international astronomical community.

Reference

Over the next 15 years or so, Denning became universally acknowledged as one of the finest planetary observers of his age, and especially of Jupiter. Having access to the best astronomical literature of the day, he became acutely aware that the drawings made by astronomers using larger telescopes were not revealing as much detail as one might have anticipated from their superior aperture. As a case in point, he argued that the Jovian whole disk drawings carried out by the Third Earl of Rosse using the 72 inch Leviathan of Parsonstown were no more detailed than backyard telescopes with very modest apertures in comparison. In addition, being intimately familiar with the work of other great observers of his era, such as the English solicitor and amateur astronomer, Stanley Williams, who had used a 6.5 inch Calver reflector on a simple equatorial mount to make all of his highly detailed drawings of the Giant Planet, Denning reached this remarkable conclusion in a publication communicated in 1885:

Many people would consider that in any crucial tests the smaller instrument would be utterly snuffed out: but such an idea is entirely erroneous. What the minor telescope lacks in point of light it gains in definition. When the seeing is good in a large aperture, it is superlative in a small one. When unusually high powers can be employed on the former, far higher ones proportionally can be used with the latter. We naturally expect that very fine telescopes, upon which so much labour and expense have been lavished, should reveal far more detail than in moderate apertures, but when we come to analyze the results it is obvious such an anticipation is far from being realized. The glare of excessive light and the endless mouldings and flaring of the image can only have one effect in obliterating delicate markings.

Reference

Denning’s comments were made in response to some criticisms of both his work and the observations made by other keen observers he enjoyed correspondences with, who seemed to confirm rapid atmospheric changes in Jupiter’s massive turbulent atmosphere. In particular, they were directed at the comments made by the professional American astronomer, G.W. Hough, who employed the 18.5 inch Dearborn refractor in his own Jovian studies, but who had failed to notice the same changes. Consequently, Hough dismissed the reports of Denning et al as being attributed to “the poor quality of the images” in the smaller telescopes. Rising to Hough’s criticism, Denning not only reaffirmed what he and others had seen but began to seriously wonder why Hough had missed seeing these changes with such a formidable telescope. In another 1885 publication, Denning writes:

Apertures of 6 to 8 inches seem able to compete with the most powerful instruments ever constructed……a very large aperture shows the rushing of vapours across the disc, and violent contortions of the image, which are the inevitable result.

Reference

In support of his conclusions, Denning pointed out that the disk drawings of Mars made by Asaph Hall and the Scots-born American astronomer, William Harkness,  were noticeably ‘bland’ in comparison with those drawn by the Reverend Dawes and Giovanni Schiaparelli, who both used instruments of 8-inch aperture, as well as the fine work of the British artist, Nathaniel Green, who had conducted extensive Martian observations from the Madeira archipelago, off the coast of Morocco, using a 13-inch silver-on-glass reflector.

Reference:  Sheehan, W, Planets and Perception, University of Arizona Press, (1988), pp 103.

In addition, Denning also brought Sir William Herschel’s opinions in these matters to the fore:

Sir William Herschel seems to have the non-utility of large instruments in the observation of bright planets for he wrote as follows: “On the course of these observations[on the belts of Saturn] I made ten new object specula and fourteen small plain ones for my 7 foot [6.3 inches] having found that with these instruments I had light sufficient to see the belts of Saturn well and that here [Bath, England] the maximum of distinctness might be much easier obtained than where large apertures were concerned.

After Nathaniel Green acquired his ‘ultimate’ telescope back in England – a reflector of 18 inches aperture – he found it useful to fit it with a “convenient gradation of stops.”

This was just the ammunition Denning needed to drive home his own findings:

If a large diameter telescope is useless without stops, wherein does its utility consist? Better at once to adopt a smaller speculum and obviate the more troublesome manipulation of a large instrument. True there are very rare occasions when all the aperture may be utilized; but are they worth waiting for, and when they come, do the results answer expectations?

Reference

Denning undoubtedly had a point, as the air cells coursing over the British Isles do indeed seem to favour moderate but not large apertures, but it was not true everywhere. For example, in a study conducted by the American astronomer, Charles A. Young, using the 23-inch Clark refractor at Princeton, New Jersey, he admitted that while small apertures are less sensitive to the vagaries of the Earth’s atmosphere, in his opinion, the images through the 23-inch were generally far superior to those garnered by the 9-inch glass with a frequency of about one night in three.

Notwithstanding these comments, Denning was no Luddite, acknowledging that for other avenues of astronomical observing, aperture was an indispensable commodity:

In certain departments of research large apertures are absolutely required, and have performed work utterly beyond the capacity of moderate instruments.

Reference

Denning’s keeness for observing was legendary, so much so that it is no wonder he did so well with such a modest telescope without a driven mount, and no cooling fans; a circumstance that flies in the face of the modern amateur, who often regard such devices as ‘essential.’ Denning’s reports are also entirely in keeping with the author’s own field experience with a modern 8-inch f/6 Newtonian, which has proven to be his best and most used telescope (also un-driven and with no cooling fans).

We may gain a glimpse of Denning’s extensive experience by taking a look at a few comments he made in Chapter VIII of Hutchinson’s Splendour of the Heavens:

The telescope’s definition of Jupiter varies greatly according to the altitude of the planet. From 487 nights of observation (ten inch reflector) at Bristol the following percentages were observed:-

% Nights                                 Very Good         Good        Fair         Bad       Very Bad
Jupiter South of Equator            7.0                 14.1         15.5         33.8           29.6
Jupiter North of Equator           19.8                 29.1         25.6         18.6             7.0

The reader will note the great advantage of observing the planet higher in the sky as viewed north of the celestial equator, where the orb is less affected by atmospheric turbulence. Note also the percentage of useful nights and/or observing spells Denning enjoyed from Bristol; a number wholly inconsistent with the ‘perpetual bad weather myth’ promulgated by modern amateurs. Self evidently, there were more clear nights where work could be done over ‘cloudy’ England than is commonly reported today.

Reference: Philips, T.E.R (ed.), Hutchinson’s Splendour of the Heavens, Vol 1, Hutchinson & Co, (1923), pp 337.

Intriguingly, this anomalously high frequency of good observing nights/spells communicated by Denning was also independently reported by the consummate British amateur, Charles Grover, who’s biographer revealed that he observed on 146 nights (40 per cent) during the year 1886.

Denning was a keen observer of Jupiter’s Great Red Spot (GRS), watching it change in colour, shape and size over many years with his 10-inch With-Browning speculum, and about which he discusses at great length in Splendour of the Heavens. On the evening of February 13 1888, he made a sketch of the Giant Planet with his alt-azimuth reflector, which shows a considerable amount of detail.

Denning's sketch of Jupiter dated February 13, 1888 showing the unusually large GRS and bright cloud within its confines. Source: http://www.phenomena.org.uk/page105/page131/page131.html

Denning’s sketch of Jupiter, dated February 1888, made with his 10-inch Calver reflector, showing the unusually large GRS and bright cloud within its confines.
Source: http://www.phenomena.org.uk/page105/page131/page131.html

The size of the GRS is relatively enormous though, much larger in comparison to anything seen in recent years. The reader will note a large bright cloud-like structure encapsulated within the spot. Out of curiosity, this author examined another Jupiter drawing by the young E.E. Barnard using a fine 5-inch f/15 Byrne refractor, made as close in time as possible to Denning’s sketch. As this link shows (bottom right sketch) dated April 22, 1886, Barnard’s superb eyesight recorded an equally large GRS with the same cloud like structure inside it, and with an accompanying note (seen on the previous page) which states:

A white cloud has formed over the middle of the Great Red Spot, almost obliterating it.

Could Denning and Barnard have observed the same feature, albeit a couple of years apart? I dare say, it’s very probable!

Do you have the historical evidence to dismiss this possibility out of hand? I’d be happy to  weigh the evidence.

Comparing the detail of the two sketches, we see the superior resolving power and contrast transfer of Denning’s reflector coming into play, don’t you think?

Denning’s contribution to planetary astronomy extended well beyond Jupiter though. For example, in 1876, Professor Asaph Hall using the great 26-inch refractor at the U.S. Naval Observatory, recorded an equatorial spot on Saturn, which he followed and measured through 60 rotations, and from these data deduced its period to be 10 hours, 14 minutes and 24 seconds. Hall was careful to stress that this may not have been the rotation period of the planet per se, only that of the spot itself. Back in England, both Denning and Stanley Williams, using far more modest 10 inch and 6.5 inch specula, respectively, were following vague markings on the Saturnian globe and came to a rotation period just two seconds shy of Hall’s estimate, all of which are in agreement with the best modern values for the planet’s rotation.

Reference: Clerk, A., A Popular History of Astronomy During the Nineteenth Century, Cornell University Press, 2009, pp 167

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An Aside: Quality Never Goes Out Of Fashion

How good were With and Calver mirrors?  In a word, ‘excellent’, by all accounts. Calver deliberately left his mirrors slightly undercorrected to compensate for the natural overcorrection a mirror would exhibit as it cooled off. This is also the case with the majority of modern, mass produced mirrors. A few years back, I had the pleasure of conversing with London-based amateur astronomer, Robert Katz, who lovingly restored a magnificent 10-inch f/8 Calver reflector on a simple alt-azimuth mount. He was kind enough to share his experiences of the telescope with me.

My f8 10″ Calver looks like an unwieldy beast and by any modern standards is overwhelmingly long. The original wooden stand had rotted and was missing its slow motion controls when I found it, but luckily Len Clucas, the former professional telescope-maker for Grubb Parsons in Newcastle had inherited an identical stand and cradle from the late master mirror maker David Sinden which he refurbished for me. A stepladder is essential for objects over 30 degrees high and viewing near the zenith is positively dangerous. And yet – climbing up to the eyepiece apart – it is remarkably easy to use. The eyepiece is always in a convenient position – assuming you can reach it – the azimuth and altitude controls are smooth and make tracking easy even at powers of 300x and the ingenious system of a clamped tangent arm makes rewinding the azimuth screw simple without losing position. Even though it weighs a ton the telescope is also beautifully balanced; unclamped from the slow motions, with a 40mm eyepiece in the barrel, I imagine it is the closest you can get to the laid-back star-hopping Dobsonian experience with Victorian equipment.

The optics are fine and because the focal length is actually less than that of a standard SCT, views of deep sky objects are impressive with a low power eyepiece. It comes into its own with the planets, though, and the exceptional opposition night of Jupiter in September 2010 was memorable in many ways. Thanks to good seeing in South West London – the telescope is in Hampton Hill – I spent most of the night watching Jupiter turn in exquisite detail using a fine telescope made in 1882 by one of the two great telescope makers of his day; but a telescope so simple that a child can learn to operate it confidently in five minutes. 

A lovingly refurbished 10" Calver reflector. Image credit: Robert Katz

A lovingly refurbished 10″ Calver reflector. Image credit: Robert Katz

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thus, by all accounts, these fine Newtonian telescopes were first rate tools that enabled their owners to conduct detailed studies of the firmament. The fact that Denning and others used an alt-azimuth mounting to conduct his planetary studies  (most of which was published in the best astronomical journals of the day)  is also to be noted. Today, there is a tendency among some amateurs to dismiss the use of an undriven alt-azimuth mount because it doesn’t keep the planet in the centre of the field. Truth be told though, there will be plenty of opportunities (his was a f/7ish remember?) when the finest details of a planet’s aspect can be made out as it crosses the field of view, as this author has discovered over several years of continued work with simple, undriven mounts. So, like everything else in life, intrepid folk always find a way ’round such technical ‘obstacles’.

………………………………………………………………………………………………………………………………..

In parallel to his growing interest in planetary observing, Denning took up the activity of comet hunting sometime in the 1870s, and he was rewarded  for his efforts in the predawn hours of October 4 1881, when, shortly after a spell observing Jupiter, he inserted a low power eyepiece and began sweeping the sky in its vicinity. Almost immediately he caught sight of a ‘suspicious’ object that turned out to be a new short period comet. Nearly another decade elapsed before discovering his next icy interloper, which he stumbled upon in 1891 and this was followed by two other comet discoveries in 1892 and 1894. For each of these discoveries, Denning was awarded the Bronze Medal by the Astronomical Society of the Pacific. Denning was also the co-discoverer of a comet with the famous Americcan astronomer, E.E. Barnard in 1891.

His publication rate rising to some 20 articles per year, Denning’s reputation as an observer of repute grew steadily, so much so that he was elected President of Liverpool Astronomical Society for the year 1887, increasing its already large membership from 440 to 641.

In addition to his published articles, Denning embarked upon writing books on amateur astronomy. While his earliest forays into this brave new world was met with unnecessarily harsh criticisms from the priggish founding editor of Nature, Sir Norman Lockyer, his later books, including, Telescopic Work for Starlight Evenings (1891), were enthusiastically endorsed by the powers that be.

Many more accolades were bestowed upon F.W. Denning in the closing decade of the 19th century, not only at home but abroad also. The Valz Price of 1895 was awarded to him by the French Academie des Science, and in 1898 Denning received the prestigious Gold Medal of the Royal Astronomical Society in recognition of his monumental work on meteors. He was even given a mention in chapter 2 of H.G. Wells’ famous novel: The War of the Worlds, which was first serialised in 1897.

While it is undoubtedly true that Denning  expressed an interest in the Martian canal theory, he was not convinced of their reality stating that, ” they were far more highly suggestive of natural than artificial production.

Reference

It is not known exactly when Denning acquired his largest telescope, a 12.5 inch Calver reflector, but what is certain is that he never acquired equatorial mounts for any of them. Nor did he bother building an observatory for his telescopes; a custom quite out of sink with the prevailing culture of his day. His voluminous drawings of all the major planets are not striking for their artistic renderings but they do reveal the workings of a true telescopic draughtsman, where accuracy and objective truth were held in higher esteem than artistic license.

By the end of the 19th century, W.F.Denning was one of the most famous astronomers in the world, commanding an extraordinary web of correspondence with the scientific giants of his age. And while the accolades kept piling up, Denning’s reaction to this new-found fame was not in keeping with a man of his standing. An admixture of declining health and bitter criticism over his ideas regarding the stationary nature of meteor radiants, conspired to alienate the consummate English amateur so much so that he eschewed the limelight and became increasingly reclusive, giving up telescopic astronomy altogether by 1906.

It is not known how Denning made a living in the last few decades of his life, but it is known that he did receive a Civil List Pension by the British Government beginning in 1904, when he was 56 years old. This amounted to an annual stipend of £150, “ in consideration of his services to the Science of Astronomy, whereby his health has become seriously impaired and of his straitened circumstances.” And while there is no evidence that he earned an income from the family accountancy business, it has been suggested that he received  sporadic payments for his literary works, and some occasional prize money for his discoveries that just barely kept the wolf away from the door.

Reference

Though he lived a solitary life, Denning kept up communication with the outside world through his many letters of correspondence and scientific publications. And while his telescopic career was now far behind him, it was by no means the end of his discovery days. In a singular period between 1918 and 1920, Denning, now a septuagenarian, observed a nova in Aquila (V603 Aql), the discovery of which was later contested. However, during a routine meteor watch in August 1920, the 72 year-old Denning discovered a new star in Cygnus, shining with a magnitude of 3.5.  Nova Cygni was the talk of the astronomical world for many months to come and he enjoyed a surge in correspondences from an adoring international following.

Reference

As well as his correspondences, Denning took to writing poetry, in which he often explored the themes of Nature, her cycles of decline and renewal. It has been suggested that he was a Christian.

The last decade of Denning’s life is one of great sadness. Upon visiting him at his last known address at Eggerton Road, Bristol, in 1922, Dr. W.H. Steavenson recalled meeting a wretched soul, living in abject poverty, and with only an open fire and a tobacco pipe as sources of comfort. Even when Denning left the house, he became the butt of every schoolboy’s joke, who ignorantly taunted the eccentric astronomer .

Denning remained an active observer of the heavens right up until a few weeks before his death, aged 83, caused by heart disease, on June 9th 1931. Entirely self taught, and arguably the most active and gifted observer of his generation, he will be remembered for his unbridled enthusiasm for his science, his love of nature and for his encouragement of a new generation of stargazers across the world. W.F.Denning (1848-1931); an extraordinary life lived.

De Fideli

Tales from the Golden Age: Thomas Harriot; England’s First Telescopist.

Thomas Harriot ( 1560-1621); England's first telesopic astronomer.

Thomas Harriot ( 1560-1621); England’s first telesopic astronomer.

 

 

 

 

 

 

 

 

 

 

 

 

What is remarkable and possibly says much about Harriot’s personality, is that he expressed only admiration for Galileo without the slightest trace of jealousy.
Dr. Allan Chapman.

The mid-16th century was a period of tumultuous change in Europe; the Protestant Reformation having swept across the kingdoms of the north, whilst in southern Europe, Roman Catholicism still held sway. The bulwark of the Renaissance had introduced radical new ideas in science, architecture, politics, art and literature, inspired by a palpable sense of nostalgia for the triumphs of classical antiquity. Knowledge, for so long the preserve of the rich and powerful, was now being disseminated at a hitherto unprecedented rate to the proletariat. The printing press had empowered a new generation of scholars with the fruits of human knowledge, not just in Latin, but in the mother tongues of the various kingdoms, principalities and nation states of a new and self-confident Europe.

This was the world that Thomas Harriot was thrust into, born sometime in the year 1560, in the county of Oxfordshire, England. Though he likely had a sister, his ancestry remains somewhat of a mystery to modern historians, and the first we hear of Harriot comes from his matriculation to St. Mary’s Hall, a daughter house of Oriel College, at the University of Oxford, on December 20, 1577. In order to matriculate, Harriot would have had to demonstrate a mastery of classical Latin and Greek, both spoken and written, as well as the Bible, the pillars of knowledge upon which all prospective Tudor scholars were encouraged to embrace. We can infer from this that Harriot’s family placed great value in education for its own sake and that they had sufficient wealth to prepare the youth for such a career, a circumstance that the majority of children could not yet enjoy.

At St. Mary’s College, Harriot would have been absorbed in what we might call a ‘classical’ education, with its strict adherence to Latinity, supplemented by rhetoric and argument, the elements of Protestant theology and civil law. Any graduate worth his salt would be expected to present and debate complex ideas in order to excel in the three principal career options open to him; jurisprudence, the Church and Parliament. This education would also include a thorough grounding in mathematics, geometry and Ptolemaic cosmology. It was in these latter studies that Thomas Harriot would excel.

It was most likely here also that Harriot first came to the attention of Walter Ralegh (1552-1618), eight years his senior, and himself a graduate of Oriel College. By his late twenties, Ralegh had established a great name for himself, both at home and overseas, as a naval commander, scholar and showman, having the ear of the Virgin Queen herself. By this time, England had become a formidable maritime power with an imperious outlook, and Ralegh had set his sights on the colonisation of the eastern Atlantic seaboard of North America. To make this a reality though, Ralegh was always on the lookout for young and enterprising officers with a mathematical penchant, to conduct the surveys, the proper execution of various censuses, as well as the creation of maps of these new territories. It was in this capacity that Harriot entered the employ of Ralegh, who bequeathed him an opulent apartment annexed to his own mansion at Durham House, on the banks of the River Thames.

Harriot’s first mission was to accompany Sir Richard Greenville, himself under the auspices of Ralegh, to Virginia, on board the Tiger, which set sail in the Spring of 1585. His duties were to thoroughly survey the hinterland of the small, Christian settlements that had sprung up around the territory of Roanoke, to learn the language and customs of the native Americans and, if possible, to purchase land from them. This was not to be a bloody enterprise however, with the usual spate of rapine pillaging. The land would be honourably acquired with a spirit of honesty and fair treatment, a circumstance that was aided substantially by the vastness of the New World and its sparse indigenous population. Ralegh had already brought two young men from the Algonkian nation, Wanchese and Manteo, back to England to immerse them in the cultural nuances of  Elizabethan London, and, whilst there, were given the freedom of Durham House, before being repatriated, under the aegis of Harriot, in their native Virginia.

By all accounts, Harriot carried out his duties with great diligence and enthusiasm, learning the ‘queer’ tongue of the Algonkians and immersing himself in their rich culture and religious beliefs. Although one of the goals of such a mission was to take the Christian faith to the native Americans, it was not to be imposed. That said, Harriot found no shortage of Algonkians who embraced the life of Christ, finding that their truths were part of a greater truth.

Harriot produced a famous treatise, A Briefe and True Report of the New Found Land in Virginia, published in 1588, of his dealings with the peoples of this new territory, and marking him out as arguably the father of modern ethnology.

According to Dr. Allan Chapman, a renowned historian of science at the University of Oxford, and fellow Christian, whom this author has had the immense pleasure of conversing with on several occasions, Harriot could also be said to be the founding father of scientific education in North America. In his True Report, Harriot appeared to give a lecture, presumably in the Algonkian tongue, to a native American audience, who were dumb struck by the cleverness of the scientific instruments he brought with him from England:

Mathematicall Instruments, Sea Compasses, the virtue of the Loadstone in drawing yron, a Perspective Glasse which shewd manie strange sightes. Burning Glasses, wide fire woorkes, Gunnes…Spring Clocks that seem to goe of themselves, and many other things that we had.

Some historians have used the accounts of the various optical devices described in his True Report, as evidence that there may have been a ‘Tudor telescope’,significantly predating those eventually acquired by Harriot. Yet, as Chapman points out in his book, Stargazers, Copernicus, Galileo, the Telescope and the Church, this is a classic case of reading too much into the literature:

The strange sights and images which seemed to perplex and even alarm the Roanoke locals, I suspect were probably no more than the facial and other distortions that anyone can see in a convex or concave mirror.

pp 261

Thomas Harriot was an accomplished mathematician; one of the finest in England. Most notably perhaps, he introduced the symbols for less than (<) and greater than (>) which are used to solve inequations. Harriot also did original work on the binomial theorem, which is an eminently useful technique for the expansion of algebraic expressions raised to any power.

When Ralegh asked Harriot to investigate the science of gunnery in the 1590s, he applied a vector based technique to resolve the projectile’s velocity into horizontal and vertical components and was able to deduce that its path fitted that of a parabola; an essentially modern analysis. He did however retain some outdated (and completely incorrect) ideas on motion, adhering to the ancient Aristotelian idea that heavier objects fall to earth faster than lighter objects.

Having a life-long interest in optics, Harriot formulated a theory of refraction in 1601, noting that when a ray of light passes from a thinner to a denser medium, the angle to which it is refracted from the point at which it enters the glass is always in the same proportion to the angle at which the ray first strikes the glass. This result, known more generally as Snell’s Law, was independently discovered by the Dutch scientist Willebrord Snellus (1580-1626) in 1621.

After Queen Elizabeth I died in March 1603, ending the line of the Tudors, James VI of Scotland ascended to the throne as James I, uniting the crowns of England and Scotland in the process. The new King, unlike Elizabeth before him, strongly disliked Sir Walter Ralegh. Indeed, just a few short months after the passing of Elizabeth, James I had Ralegh put on trial for treason. Though many scholars now consider the evidence against him to be specious at best, he was found guilty, sentenced to death, inexplicably reprieved from the gallows and condemned to spending the rest of his days under house arrest in the Tower of London. Despite this change of events, Harriot visited Ralegh at the Tower on many occasions, remaining loyal to his friend and patron.

It is important to remember that though Ralegh were imprisoned in the Tower, he still enjoyed considerable liberties, uncannily similar to Galileo’s ‘house arrest’. A far cry from the dark, dank and rat infested dungeons, they were given comfortable lodgings, enjoying fine food and drink, and freedom to roam within its walls, attend Church, and carry out day to day investigations and studies. Even their families were permitted to live there. So, despite his ‘imprisonment,’ it was still possible for Ralegh to live out a reasonably fulfilled life.

Harriot himself was not immune to the suspicions of the new regime, having being imprisoned in the Tower for three weeks, cross examined but summarily released in November 1605. Harriot’s loyalty was rewarded when Ralegh recommended him to Henry Percy, the Ninth Earl of Northumberland (1564-1632), who was also imprisoned for 17 years in the Tower for being a Catholic sympathiser and for his alleged involvement in the plot to blow up the Houses of Parliament in 1605. Fabulously wealthy, the ‘exotic’ Percy was rumoured to have spent an unprecedented £50 a year on books and employed Harriot to carry on his scientific investigations. For this he was given a very generous stipend and access to Percy’s stately southern residence at Syon Park, Brentford, London and a comfortable residence at Threadneedle Street in the city. Overnight, Harriot not only became financially independent but was now the richest mathematician in Europe, commanding a salary estimated to be ten times greater than the best paid academics of the age!

According to his 17th century biographer, John Aubrey, Harriot waded into all of the pressing astronomical questions of his day. “He had seen nine Cometes,” wrote Aubrey, “and had predicted Seaven of them, but did not tell how.” Intriguingly, according to Dr. Chapman, Harriot may have co-discovered the elliptical nature of the planetary orbits traditionally ascribed to the work of the German astronomer and mathematician, Johannes Kepler. According to his friend and protégé, Sir William Lower, while pressing his master to compile a list of notable scientific achievements later in his life, left this tantalising snippet:

“……..long since you told me as much [of Kepler], that the motions of the planets were not perfect circles,” and that the planets made their, “revolutions in Ellipses”.

In this matter Chapman leaves us with a proverbial cliff hanger, raising the question: “One wonders exactly how long since?”

Ibid pp 265

What is certain, however, is that Harriot, being a geometer of some renown and thus intimately acquainted with the mathematics of orbits, would have had extensive correspondence with the other great intellectuals of the age, Johannes Kepler included. Furthermore, there is no evidence that Harriot cultivated the notion that he had arrived at the formula of the ellipse to explain the orbit of Mars. Indeed, in stark contrast to the vast majority of learned men of his time, Harriot never published anything after his True Report of 1588, which came as a source of considerable irritation to his patrons, who wished only to seek glory for his accomplishments, as well as to his friends, who watched in anguish as others trumpeted their ‘discoveries’, which were probably best attributed to Harriot himself. This was a characteristic that was to set Thomas Harriot apart from his contemporaries, who invariably identified knowledge with power. Perhaps a quote from King Solomon can help the reader grapple with this peculiar attitude to his work;

And I turned myself to behold wisdom, and madness, and folly: for what can the man do that cometh after the king? even that which hath been already done.

Then I saw that wisdom excelleth folly, as far as light excelleth darkness.

 The wise man’s eyes are in his head; but the fool walketh in darkness: and I myself perceived also that one event happeneth to them all.

Then said I in my heart, As it happeneth to the fool, so it happeneth even to me; and why was I then more wise? Then I said in my heart, that this also is vanity.

Ecclesiates 2:12-15

Despite vigorous researches over many decades and centuries, historians of science cannot unequivocally attribute the invention of the first refracting telescope to any one individual. And though rumours abounded that there were telescopic devices significantly earlier than those that came on the scene in the early 17th century, it is undoubtedly the case that the enterprisng spectacle maker, Hans Lippershey, based in the Dutch town of Middleburg, tried but ultimately failed to secure what would have been a lucrative patent in 1608 from the Dutch States General for the simple telescopes he constructed.

As a result, the device, which consisted of a matched pair of convex and concave lenses arranged in a tube, could be fashioned and sold by anyone once the proverbial cat was out of the bag. It is likely that Harriot acquired an early ‘dutch trunke‘ or ‘cylinder‘ from one commercial source in Holland early in the year 1609. Possible clues to the construction of the instrument can be viewed at the bottom of this Telescope 400 link

From the grounds of Syon Park, Harriot and his assistant, Christopher Tooke, set up the telescope, magnifying just 6 times, on the fair evening of July 26, and at 9pm turned his instrument on a five-day-old crescent Moon and began to sketch what he saw. Various mare are included in the sketch including the Mare Crisium, Tranquilitatis and Fecunditatis, as well as some rugged lunar features situated along the terminator, which modern scholars have identified as Theophilus and Cyrillus. Curiously, this first sketch, which can be seen in this link, does not record any craters, although 6x is certainly large enough to resolve several of the more prominent ones.

A spyglass like this launched the telescopic career of Charles Grover.

The author’s 6x achromatic spyglass used to substantiate Harriot’s observations.

Out of sheer curiosity, in a separate investigation, this author used a modern spyglass with an uncoated, one inch diameter object glass, also having a magnification of 6x, in the wee small hours (01:30h UT) of January 1 2016, to record observations of the last quarter Moon and Jupiter, as they cleared the treetops in the eastern sky. Like Harriot’s telescope, the spyglass gives an erect, correctly orientated image but enjoys a much larger field of view (~ 4 angular degrees). Nonetheless, this author could confirm that many lunar craters can indeed be observed with a steady hand, as well as clearly showing various maria. Turning to Jupiter, then just a few degrees above the Moon, the telescope could clearly reveal four Galilean satellites all to one side of the planet. The author made a sketch of this sight, shown below;

A quick sketch made by the author using a 6x achromatic spyglass showing the positions of the 4 Galilean satellites positioned to the northwest of the planet at 01:30h UT, January 1st, 2015.

A quick sketch made by the author using a 6x achromatic spyglass showing the positions of the 4 Galilean satellites positioned to the northwest of the planet at 01:30h UT, January 1st, 2016.

It will come as somewhat of a surprise to the modern reader not acquainted with a Galilean telescope that, despite its very low magnifying power, its field of view was very restrictive – typically 15 to 18 minutes of arc, or just over half the diameter of the full Moon. As a result, Harriot could not have seen the entire countenance of the crescent. Incredibly, though Harriot made many more drawings of the Moon, some of which display far more cartographic details than Galileo’s later drawings, were left undated. This has proved frustrating from the point of view of the modern historian, although when we take into account the radically different personalities of both Galileo and Harriot, we can see that both men had entirely different agendas. Harriot, having spent time in Virginia, was a draughtsman and well acquainted with map making. His methods were slow and methodical. Harriot was not seeking fame and fortune in the same way that Galileo was, and, according to Dr. Chapman, because Harriot had two high profile friends on ‘death row’ in the Tower, he had little desire to make himself ‘conspicuous.’

Ibid, pp  268.

By the winter of 1609, Harriot despatched Tooke, his able technician, to the residence of Sir William Lower at Trefenti, Carmarthenshire, South Wales, instructing him to fashion several other Galilean cylinders so that he and his philosophical friends, a one Mr. Vaughan and Mr. Protheroe (and possibly a few others), could begin their own telescopic investigations of the Moon and other celestial bodies. The surviving exchanges between Harrriot and the ‘Carmartenshire philosophers’, clearly reveal their avowed acceptance of the Copernican system as well as Kepler’s elliptical orbital theory. This is the earliest known record of an ‘astronomical society’, the members of which were to confirm Galileo’s monumental telescopic work by observing the Galilean satellites and the erstwhile invisible stars in the Pleiades.

Over the next few years, Harriot was to complete his now famous Moon maps as well as embarking upon a detailed study of the Sun. His method involved observing the Sun when it was near the horizon and veiled behind mist and thin cloud (the reader should, under no circumstances, attempt such an observation!!). Harriot was the co-discover of sunspots, recording them at or about the same time as Galileo, and possibly earlier than Christopher Scheiner (1573-1650) and Johannes Fabricius (1587-1616), which, in themselves, provided more evidence against the time-honoured cosmology of Ptolemy.

Christoph Scheiner( 1573-1650), the Jesuit priest and astronomer

Christoph Scheiner( 1573-1650), the Jesuit priest and astronomer, with his telescope featured to his left.

 

 

 

 

 

 

 

 

 

 

 

 

 

Over the next two years, Harriot was to carry out some 450 observations of the Sun, never once claiming their discovery, observing how they moved across its otherwise brilliant face, breaking up and sometimes even disappearing. Indeed, modern scholars were able to establish a solar rotation period of 27.154 days from Harriot’s drawings – uncannily close to the modern accepted value of 27.2753 days. This affirms the accuracy and attention to detail so central to Harriot’s modus operandi.

According to Dr. Chapman, Tooke may have made improvements to the basic Dutch ‘trunke’ and referrring to a study conducted by the distinguished historian of astronomy and cosmology, the late Professor John North (1934-2008), identified no less than six telescopes associated with Harriot and the ‘Trefentine’ philosophers, ranging in power from 6x to 50x.

ibid, pp 272

Tooke is likely to be the first bona fide telescope maker in Britain, an optical tradition that was to be continued over the following centuries.

Although Harriot embraced the Christian message from his youth, even writing the Lord’s Prayer in the Algonkian language, some scholars have suggested that he may have experienced a brief religious hiatus in his middle years. Doubtless, the revolution heralded by the application of the telescope to the celestial realm had raised new questions in the minds of his learned contemporaries. Why were the astronomical bodies puckered and imperfect? How did God create everything from nothing? Was His divine hand needed at every stage, from the formation of atoms to the completion of worlds? Was the allegory of the Universe even attributed to a personal God or was it merely blind chance?

Although Chapman acknowledges that nothing firm can be adduced from Harriot’s surviving notes and correspondences, he is inclined to the view that the world’s first telescopic astronomer re-embraced his Christian heritage in the final decade of his life, as evidenced by his 1615 correspondence with the King’s physician, Sir Theodore Mayerne, who assured Harriot of the certainty of the existence of ‘one all-powerful God’. From his days in Virgina, Harriot had taken to ‘drinking’ tobacco smoke, as the Elizabethans had referred to it. Earlier physicians had hailed the new wonder drug as an effective remedy to counter the ‘dangerous moist humours of the body.’ 30 years of heavy inhalation of tobacco smoke was to take its toll on Harriot’s health and he had developed a cancerous lesion on his nose.

Ibid, pp 273

Because many tumours of this sort have a tendency to metastasise, spreading to other organs of the body via the lymph nodes, Harriot was arguably history’s first clearly attested tobacco-induced cancer victim, dying on July 2, 1621. Receiving a full Christian burial, he was laid to rest at his local Parish Church of St. Christopher-le-Stocks, located in the heart of the City of London. And while the Church was razed to the ground by the Great Fire of 1666 and another resurrected on the original site by none other than Sir Christopher Wren (1632-1723), this too was eventually demolished in 1781 to make way for a grand new building that would became the headquarters of the Bank of England. In the 1970s however, the gravestone dedicated to Thomas Harriot was recovered and, in his honour, a new plaque carrying his gravestone inscription was unveiled inside the bank.

It is difficult to crystallize the legacy of Thomas Harriot, being so far removed from him in time, but these words come to mind; learned, diligent, enterprising, kind, loyal, uncompetitive, humble and God-fearing. Despite not marrying and raising children, he lived out a fulfilled life without a bad word to say about his fellow men, and rendered all the more remarkable owing to his great wealth and life-long connection with the rich and powerful.

England’s first telescopic astronomer, Thomas Harriot (1560-1621) gaudeamus!

Further Reading:

Chapman, A., Stargazers: Copernicus, Galileo,the Telescope and the Church, (2014), Lion Books.

North, J., The Fontana History of Astronomy and Cosmology, (1994), Fontana Press.

You can read more about the great visual observers of antiquity in my up-and-coming book, Tales from the Golden Age of Astronomy.

De Fideli

The Great Meudon Refractor

The 83cm Refractor at Meudon Observatory, Paris.

The 83cm Refractor at Meudon Observatory, Paris.

 

 

 

 

 

 

 

 

 

 

 

 

 

A Work Dedicated to the Sovereign People of France.

 

The great refractors always have their place in modern astronomical observation, through the purity and quality of their images. At Meudon, beneath the great dome, a resolving power of 14 hundredths of an arc second awaits the observer. Very few institutions in France can offer as much.

                                                                                              Dr. Paul Couteau (1923-2014)

At the beginning of the 21st Century, the stakes have changed: astronomers no longer count upon the Grande Lunette to open the way to new discoveries, but wish above all to utlise it to share with the largest number of people the passion of observation, the fascination with planets and nebulae; that will be the new career of this fantastic instrument.

                                                                                              Professor Daniel Egret

                                                           President, Paris Observatory.

Founding Days

Tucked away in a leafy southwestern suburb of Paris, amid rolling hills and valleys, and sleepy glades of chestnut and ancient oak, lies Meudon. Inhabited since Neolithic times, the Gallic incumbents called it Moldum. Under Roman occupation from the mid-1st century B.C onwards, it was known as Moldunum. The great natural beauty of the area attracted the elite in French society from these early times, its hills providing ready made vantage points for surveying and surveillance alike. During the decadent reign of Louis Quatorze, the Sun King, its most famous building, the Château de Meudon, became a favourite hunting retreat. Raped and pillaged during the Bloody Revolution, more misfortune befell the Château in 1795, when a fire all but razed it to the ground. By 1803, its demolition complete, one would be forgiven for thinking that anything good could come of it. But like the mythical Phoenix rising from its own ashes, the site had attracted many astronomers over the years and was ‘re-discovered’ by the great French astronomer, Pierre Jules Janssen (1824-1907), when he surveyed the area by balloon in the 1870s. After lobbying government officials, he persuaded them to dedicate the site to a new world power; scientific knowledge. Keen to maintain its imperial prestige, the French government commissioned Janssen with the ambitious task of building a state-of-the-art astronomical observatory on the ruins of the erstwhile stately grounds.

Demolition of the Château of Meudon by Hubert Robert.

Demolition of the Château de Meudon by Hubert Robert.

Under the aegis of Janssen, repair work commenced on the buildings, as well as the in situ restoration of astronomical equipment; kit that had been abandoned over the years and fallen into disuse. The offices and laboratories were lodged in the principal part of the estate, which formerly consisted of a modest château, stables, and an assortment of other outbuildings. A separate building, the Château Neuf, built by Mansart in 1706, was to be restored and topped by an astronomical dome 18.5 metres in diameter.

Building work commenced in 1890 and continued for five years. The chief architect appointed to the project, monsieur C. Moyaut, had all the upper wings of the château removed and restored the ground floor, being careful to preserve the stylized pediments created by Mansart at the beginning of the 18th century. In 1886, work began on the construction of a 20 metre-diameter circular space that was to form the lower walls of the observatory and upon which a rotating dome would be constructed. The obvious choice to build the dome was Gustave Eiffel, who had directed the construction of the large dome at Nice Observatory and was a personal friend of Janssen. However, it seems that Eiffel was too preoccupied with erecting the famous Parisian landmark which bears his name to commit to such a project. The contract to construct the 18.5 metre dome was thus awarded to the Anciens Etablissements Cail, a firm which specialised in large iron works and which had previous experience constructing a lesser, 12.5 metre diameter dome for the Observatory at Rio de Janeiro, Brazil. After many stops and starts and some serious injuries inflicted upon some of the workmen, the fully rotating dome was finally signed off on the morning of June 14 1895.

The state-of-the-art equatorial mounting of the refractor was erected upon a pedestal of cast iron, which in turn rested on a massive pier measuring 4.1 x 2.7 m in cross section and soaring 18 metres above the floor. The entire structure was designed and built by Paul Gautier (1842-1909) in his Parisian workshop at 56 boulevard Arago.  Structurally and mechanically, it was very similar to the mounting provided by Gautier for the newly completed 77cm (30-inch) Nice refractor, which saw first light in 1886. A spiral staircase wound its way upwards around the pier and led the astronomer to the observing platform, which could be adjusted in elevation to accommodate the changing altitude of the celestial object under study. The platform, which is 8 metres wide and 2 metres deep, is affixed to the rotating dome. The equatorial mount could subtend an arc length of 30 degrees ensuring vibration free movement for two hours, after which time an alarm sounded, summoning the astronomer to return the sector to the start of its travel, interrupting observations for a short time.

Side view of the great 77cm ( 30-inch) Nice refractor showing the design of its massive equatorial mounting.

Side view of the great 77cm ( 30-inch) Nice refractor showing the design of its massive equatorial mounting.

Dedicating the Instrument

By the end of the 19th century, the art of melting, homogenising and casting high quality glass blanks was in a relatively advanced state. Janssen commissioned the work of France’s finest opticians, the brothers Henry, to produce the crown and flint object glass for the Meudon refractor. Since 1882, they had moved their optical workshops to the Montrouge, a commune of southern Paris, and a conveniently short distance from the new observatory. Breaking somewhat with convention, the Henry brothers settled on a contact Littrow design for the main objective, which consisted of an equiconvex front lens followed by a negative lens of the same inner radius, with the last surface being flat. This design made it relatively easy to fabricate to very high standards. A second crown object glass of the same aperture was fashioned and kept in storage.

The distinguished French astronomer, Audouin Dollfus ( 1924-2010).

The distinguished French astronomer, Audouin Dollfus ( 1924-2010), who spent his entire professional career at Meudon.

According to the late Audouin Dollfus (1924-2010), resident astronomer at Meudon for 60 years between 1945 and 2005, the two large lenses had a measured diameter of 82.95 centimetres but when they were fitted inside their cell, the clear aperture was reduced to 80.6cm. The chromatic correction of the object glass was optimised at 594nm. With a focal length of 16.397 (~f/20) metres (measured at the green spectral line of mercury), it displayed some secondary spectrum at blue-violet wavelengths. That being said, according to Dollfus, this could be completely eliminated by using a simple yellow filter. The assembled object glass was mounted in its tube in 1893, a full three years before work on the revolving dome had been completed and was tested by pointing the telescope at stellar point sources that crossed the slit of the motionless dome. The quality of the images was very well documented, having being tested by some of the finest optical evaluators of the age. For example, in 1929, the famous optical tester Bernard Lyot wrote concerning the large Meudon object glass:

“When the atmospheric conditions are favourable, the objective gives perfect images, necessitating a magnification of 800.”

Dollfus, A., The Great Refractor of Meudon Observatory,pp 22

In another test, carried out on the night of May 22 1937 by staff astronomer Fernand Baldet, a star of magnitude 6.3 was examined with a power of 2,300 diameters, recording “a perfectly circular diffraction pattern surrounded by broken moving rings.”

According to Dollfus, in further tests conducted between 1966 and 1975, resident Meudon astronomer, Paul Muller, examined numerous double stars and could cleanly separate pairs as close as 0.15 arc seconds, and others showing strong elongation at 0.12 seconds of arc!

Jean Texereau, chief optician at the Paris Observatory, performed modern optical testing methods on the object glass.Wave testing showed the figure to be perfect over the central 68cm, reaching 1/4 wave P-V at its extremities. Texereau recorded a slight turned edge in the outer 5.5cm which he attributed to stress of the glass within the cell.

Collectively, these testimonies reveal that this 19th century object glass was performing at or very near the theoretical limits imposed by its aperture.

This will come as a considerable shock to contemporary amateur astronomers, who remain largely ignorant of the prowess of long focal length achromatic refractors. Furthermore, the testimonies of these professionals yet again flatly contradict the proclamations of some contemporary amateurs who have claimed that apochromatic refractors perform better. Self evidently, the latter remain an expedient luxury for double star astrometry and, as we shall see, many other enterprises besides.

Janssen was also mindful of the advances photography could bring to his science and because the 83cm refractor was designed for visual observations, he set about ways of mounting a second telescope which was to be devoted to photographic use. Thus, in essence, the Meudon refractor would not be singular but double! The best emulsions of the day – gelatin silver bromide – were sensitive to short wavelength (320-410nm) radiation and so the photographic telescope would have to have an optimum chromatic correction at 430nm. A second object glass of 62 cm aperture and focal length 15.9 metres was to be mounted alongside the visual instrument. This photographic objective saw first light in 1898 and was operated by Henri Deslandres and his assistants, who took some of the first long exposure photos of globular clusters and the enigmatic nebulae, as well as planetary surfaces. The same objective produced very high quality spectra of spectroscopic binaries and Nova Persei, which erupted onto the scene in 1901. The same instrument was used to deduce the rotation period of Uranus (via the Doppler effect) in the following year. And in 1903, the 62 cm astrograph delivered some spectacular images of Comet Borrely.

The drawtube of La Grande Lunette, equipped with a fine rack and pinion focuser, could accept six large, long focal length eyepieces offering magnifications from 220 to 540 diameters. A further half dozen short focal length oculars extended the magnification range up to an astonishing 2,300x! Remarkably, a specially designed low power, wide-angle ocular delivered an enlargement of 150x diameters and a field of view of about half an angular degree. Furthermore, an ingeniously designed metal stage equipped with two micrometer screws enabled the eyepiece to be moved up to 6 inches up or down, or from side to side, and in so doing, extending the field of view considerably. The workshops of Gautier fashioned a precision bifilar micrometer, with platinum wires to be used with the great telescope to measure the angular separation of double stars as well as planetary and satellite diameters. Sadly, the skill of the artisans who fashioned these pieces has waned in the modern psyche, being largely lost to the work-a-day world.  The effort and time lavished upon them, every last part, bit, appendage, preserves in the learned man’s eye, the true value of good work, an honest day’s grind.

And, of course, those perfect little imperfections!

These instruments were statements; they were built to last, made with human hands, hearts and minds!

To the left of the focuser was mounted a plate holder to rigidly hold the 24 x 24 cm square photographic plates which collected the focused light from the 62 cm astrograph and covered a field of view nearly three quarters of an angular degree in diameter.

La Grand Lunette was fitted with several auxiliary refractors serving a variety of purposes. The principal finder was a powerful, long focus 15cm (6-inch) achromatic telescope. It had two main functions. In the first instance, the instrument was used to assess the seeing conditions on any given night, which in turn would dictate what types of objects were to be studied and the magnifications to be employed in their pursuit. It also acted as a precision guiding telescope during long exposure astrographs taken with the 62 cm astrograph. In its earliest years of use, the astronomer would operate a handle to move the telescope in declination and a cord that enabled fine motion control in right ascension. The original clock drive, located at the base of the great double telescope, is controlled by a tangent screw which turned slowly and regularly and was powered by a heavy weight that slowly unwound from a cable affixed to a larger drum. When the weight had fallen through its maximum distance, it had to be rewound by means a large crank which demanded considerable muscle power from the astronomer who happened to be on duty.

The mechanisation of La Grande Lunette did not stand still. As soon as new technologies came to the fore, the directors of Meudon Observatory sought to assimilate them. We shall not dwell on such matters, but suffice it say that the dome and the telescope drive were eventually powered by electricity generated in situ by dynamos and gas powered motors. And thanks to the efforts of Dr. Paul Muller during the 1960s, the observing platform was eventually replaced by a moving floor, which could be precisely adjusted in height as the telescope was moved to observe objects of differing altitude. Such refinements were to maintain the great Meudon double refractor as one of the crown jewels of the French scientific establishment throughout the twentieth century.

The great double refractor at Meudon was dedicated at a time when new technologies were being employed to revolutionise our understanding of the Universe. In particular, the new science of spectroscopy was being applied to studying the celestial bodies, both in the Solar System and beyond. In January 1898, the brilliant French astronomer, Henri Alexandre Deslandres (1853-1948), was appointed as staff astronomer at Meudon and would spend the next six years applying his considerable skills at the telescope and serving as the Observatory’s Director later in his career. In particular, Deslandres had gained expert instruction in the use of the spectroscope during his time at the Paris Observatory (1889-97), where he had used the 1.2m reflector, as well as inventing the spectroheliograph, an instrument that served to greatly advance our knowledge of the Sun. Deslandres quickly set the Meudon telescope to work measuring radial velocities of stars and studying the dynamics of spectroscopic binary systems.

Since 1895, Deslandres had been devising new ways to use spectroscopy to garner information about the rotational characteristics of the planetary bodies. At the Paris Observatory, he had already obtained solid spectroscopic evidence for the rotation of the rings of Saturn, but owing to its much greater distance and smaller size, the rotational aspects of Uranus had not been elucidated. This was further exacerbated by the paucity of atmospheric features on the planet that could lend themselves to visual tracking, as well as its large axial tilt, allowing only a residual component (i.e. spectroscopically inclined) of its rotational velocity to be measured. The method was straightforward in principle but difficult to achieve in practice. Specifically, as a planet rotates, the limb approaching us displays spectral lines that are redshifted and, correspondingly, are blue shifted as they recede from us on the opposite limb. After many trials and simulations, Deslandres, together with his assistant Burton, managed to obtain high quality spectra of the planet’s limbs during the summer of 1902, and from these data, deduced something quite amazing:

“It is very probable that the planet Uranus rotates in a retrograde sense, like its satellites.”

ibid, pp 68

Using similar techniques, Deslandres measured the rotation periods of Jupiter and Saturn (and its glorious rings) to high precision.

Watchers of the Planets

Come, let us learn something of the culture of the great planetary observers of old.

To make his observations, Antoniadi installed himself behind the eyepiece of the refractor in darkness. Fixing upon a particular region of the planet’s disk, he watched the image, moving or quivering through the effects of atmospheric turbulence.He looked to seize upon the favourable moments in order to furtively catch the finest details and to engrave them upon his memory. Thus he practiced the exercise upon another region. After having thereby memorised the different configurations, he arranged them with respect to each other. Finally, leaving the eyepiece, he placed himself behind a table with an empty desktop upon the observing platform. With  pencil and eraser, he sketched upon paper at a single sitting all the memorised features of the planet.

ibid pp 77.

A time honoured sketch of Mars, made by Eugene M. Antoniadi using the Great Meudon Refractor.

A time honoured sketch of Mars, made by Eugene M. Antoniadi, using the Great Meudon Refractor.

 

 

 

 

 

 

 

 

 

 

 

 

While Meudon Observatory was never without a planetary observer from its inception, they were all eclipsed by the skilful eye of Eugene Michael Antoniadi (1870-1944). Born in Constantinople and of Greek nationality, the world was Antoniadi’s country. Cultured, refined, a man of letters, Antoniadi made his reputation in France after he had worked under the eccentric, Camille Flammarion(1842-1925), who had set up a grand private observatory at Juvisy. Flammarion, a Darwinist and leading member of the French spiritist movement, was, naturally enough, also an ardent supporter of the Martian canal theory, championed by Giovanni Schiaparelli (1835-1919) and Percival Lowell (1855-1916), having popularised in his voluminous writings, the notion that extra-terrestrial life was a cosmic certainty.

The great planetary astronomer, Eugene M. Antoniadi (1870-1944).

The great planetary astronomer, Eugene M. Antoniadi (1870-1944).

And though Flammarion was in possession of a formidable refracting telescope of 9 inch aperture (by Bardou), Antoniadi was keenly aware of the superiority of the 83cm Meudon refractor for the up-and-coming 1909 Martian opposition. Accordingly, he wrote to Deslandres, the then Director of Meudon Observatory, informing him that he would offer his services as ‘Astronome Voluntaire’. It was an offer Deslandres couldn’t refuse. Antoniadi’s most famous work on Mars began on the evening of September 20 1909, when he observed the Red Planet under exceptionally fine seeing conditions. La Grande Lunette showed him details that were hopelessly beyond the power of Flammarion’s instruments, and yet intriguingly, there was no sign of the canals. It was a revelation to the young planetary observer:

The planet appeared covered with a vast and incredible amount of detail held steadily, all natural and logical, irregular and chequered, from which geometry was conspicuous by its complete absence.

ibid pp73

Received wisdom insists that planetary sketching be done at the telescope, but that was not Antoniadi’s modus operandi. As recalled by Dr. Dollfus, he would rather commit his observations to memory before attempting a sketch. Curiously, this author ‘discovered’ the effectiveness of this method (at least for planets) whilst studying Jupiter in the 2014-2015 apparition using a 18cm Maksutov, and, more recently, using the author’s most powerful telescope.

King Solomon of old was most correct; there is nothing new under the Sun!

In so far as what is known, E. M. Antoniadi faciebat!

Antoniadi spent the next few decades, on and off, observing the planets and their principal satellites. By 1930, having amassed an astonishing array of detailed drawings of Mars, and having corresponded with other first-rate observers across the world using equally powerful telescopes, was able to lay the fabled Martian canals to rest; they were simply optical illusions. Antoniadi did however entertain a less grandiose vision of Martian life; he believed the seasonal waves of darkening that occurred during Martian Spring were tracts of vegetation. This idea was entertained right up until the advent of the Space Age.

Antoniadi’s fine drawings of Jupiter and Saturn reveal the workings of an exquisitely trained eye. The amount of detail visible through La Grande Lunette often necessitated sectional drawings of the turbulent atmospheres of the giant planets. Curiously, though the instrument could take much higher powers, Antoniadi’s sketches show that he preferred modest enlargements of 500x or so on bright planetary disks like Jupiter. This serves to remind the reader that excess powers can be counterproductive in the study of low contrast details on planetary surfaces.

Antoniadi also spent many hours drawing the various albedo features on the Galilean satellites using a routine power of between 500 and 800 diameters. Adhering to the tried and trusted culture of note making (which is sadly in great decline in the present epoch), he explained how the best details could often be made out while the satellites crossed in front of the planet, the bright background providing the contrast needed to pick off the finest details. Indeed, he claimed that observing the satellites against a dark sky was far less productive in this capacity.

The great stability of the images garnered by the 83cm Meudon refractor allowed extremely accurate micrometer measurements of the angular sizes of the Galilean satellites to be divined. What is more, the drawings he made of the surface features of these satellites enabled him to deduce that they were tidally locked, that is, presenting the same face to the planet as they orbit Jupiter. After Antoniadi’s retirement from active service, other astronomers at Meudon, including A. Dollfus, Bernard Lyot and Henri Camichel were able to assemble the first detailed maps of their surfaces in the early 1940s.

On the Physical Nature of the Planetary Bodies

The great Meudon refractor was also instrumental in advancing our knowledge of the physics and chemistry of many solar system bodies. One of the pioneering techniques developed by Meudon scientists was astronomical polarimetry. Ordinary sunlight consists of transverse electromagnetic waves that vibrate in every direction, that is, they are unpolarised. Upon reflection from a planetary body, certain planes of vibration are enhanced and others attenuated. The degree to which this occurs depends on the nature of the reflecting surface. For example, a smooth and polished surface produces a strong enhancement in certain directions, while a matt surface produces a comparatively weaker enhancement. Furthermore, opaque materials produce much stronger polarisations than that of a transparent material. What is more, the distribution of matter within a body also effects the polarisation profile obtained. For example, light reflected from a solid surface has a very different polarisation profile to that obtained from a cloud made of discrete, interspersed particles of ice or water say. By carefully studying the nature and degree of polarisation enhancement on a test object, one can also deduce the sizes of the particles comprising it.

Chief Astronomer at the Meudon Observatory in 1943 and received the Bruce Medal in 1947

Bernard Lyot ( 1897-1952) who became Chief Astronomer at the Meudon Observatory in 1943 and the recipient of the prestigious Bruce Medal in 1947 , as well as the Gold Medal of the Royal Astronomical Society.

In 1922, Bernard Lyot fashioned a prototype fringe polarimeter to be tested on a small 17.5 cm refractor, but later modified it for use with the great 83cm Meudon telescope. Once the object was centred in the telescopic field, one would look through the polarimeter and observe a series of jagged fringes representing the various polarisation enhancements, changing in intensity as the angle of inclination was varied. The device had a built-in ‘compensator’ which enabled the investigator to introduce an equal but opposite amount of polarization that nulled the individual fringes. Lyot steadily improved the sensitivity of the instrument to measure tiny polarisations, of the order of one part per thousand. The great image scale and stability afforded by La Grande Lunette enabled small sections of a given planetary body to be individually analysed, thereby recording regional differences in the physio-chemical makeup of the body.

Turning the great refractor upon the Moon, Dr. Lyot was able to reach a remarkable conclusion;

The Moon must be covered by dusts having a composition similar to that of our terrestrial volcanic ashes.

Ibid pp 97.

The planet Venus, long shrouded in mystery, also yielded some of her secrets under the watchful eye of La Grande Lunette. The polarisation curves obtained for this planet were strikingly different to those obtained for other bodies where the reflection came from a solid surface. Instead, Lyot deduced that the data was consistent with an upper atmospheric layer consisting of very fine droplets, some 2 microns in size, and having a refractive index  ‘within the range of water’ (1.33)

As the technique was refined and extended to other wavebands in later years, stretching into the infrared and ultraviolet, Meudon astronomers were able to detect innumerable transparent particles in the Cytherean atmosphere, spherical in form, with a radius of 1.05 microns, and a refractive index of 1.44. The substance that best fitted these data was concentrated sulphuric acid!

When Lyot applied these techniques to Mars, and in particular, having compared the polarimetry curves of the so-called ‘seas’ and ‘continents’ he concluded that there was little to choose between them and that if anything, they resembled the dusty surface of the Moon. Lyot’s pioneering polarimetry measurements also could distinguish between yellow dust clouds, and whiter clouds, often seen on the morning limb of the planet, composed of transparent particles, more characteristic of hoar frost or some such. Little by little, the unbridled machinations of mankind were being tempered by the unrelenting march of scientific progress.

Exploring the High Energy Universe
In the wee small hours of December 13 1934, the English amateur astronomer, Manning Prentice, observing from the small market town of Stowmarket, Suffolk, discovered a magnitude 3.4 star that was previously invisible in the constellation of Hercules. The nova reached its peak brightness of +1.5 just over a week later, on the evening of December 22. When the astronomers at Meudon were alerted to this nova La Grande Lunette was set to work to record its spectrum. During a three week period during March 1935, staff astronomer, Henri Camichel had managed to obtain 32 spectra of the object, which by then had faded back to magnitude 4.1, remaining so until month’s end after which it slowly faded out of view. The spectra revealed numerous emission lines, some known and some unknown, which were broadened with two equal maxima with a separation that corresponded to radial velocities from 590 to 870 km/s.

Visual inspection of the system by the staff astronomers at the Lick Observatory atop Mount Hamilton in California, revealed a stellar companion on the evening of July 4 1935. This was followed up by observations carried out by Fernand Baldet at Meudon, who charged the 83cm refractor with powers of 1600x to 2,300x confirming the duplicitous nature of the system. Baldet’s notes showed the stars to be of similar colour, separated by a mere 0.25 arc seconds but with no trace of nebulosity. By taking long-exposure spectra of the system into the autumn of 1935, Camichel was able to establish the essential nature of a cataclysmic variable star:

One can account for the particulars of the spectra by supposing that the star, at the moment of its peak brightness, ejected gaseous masses which were illuminated according to the excitation mechanism for planetary nebulae…. One could explain the doubling of the emission lines in terms of two very large masses moving in opposite directions. That hypothesis seems to be confirmed by the fact that the star was seen to be double.

Ibid pp 106

It is noteworthy how so many of the astronomers who, having used the great Meudon refractor for ultra-high resolution studies, spoke so highly of its virtues. Indeed, according to Dr. Dollfus, “It allowed visual scrutiny with very high magnifications, each time it was necessary.

ibid, pp 107

Once again, testimonies like these stand in sharp contradistinction to contemporary perceptions of the classical achromat, which unfortunately, are born of ignorance more than anything else.

Closing Years of Active Service

La Grande Lunette continued to be used though the latter half of the 20th century, its doors constantly opened to new generations of enthusiastic observers. Dr. Paul Muller, mentioned earlier, arrived at Meudon in 1956 after a spell at Strasbourg Observatory. Muller conducted a grand series of close double star measures with the telescope, collating his results in three publications. Systems as close as 0.12 seconds of arc were recorded in this archive. Another example is to be found in the work of the Japanese amateur astronomer, Shiro Ebisawa, who, beginning in 1968, travelled to Meudon to use the great refractor to continue his planetary studies for a few weeks at a time. A Mars specialist, Ebisawa made many fine drawings of the planet with the great refractor, as it progressed through its seasons. One new feature credited to Ebisawa’s impeccably trained eye is the so-called pre-polar hood, which manifests itself in the autumn of each Martian year and which preceded the deposition of fresh ice layers on the planet’s polar caps.

A very special event was celebrated at Meudon from July through December of 1988, when the Martian orb would once again swell to 24 seconds of arc, just as it did in that faithful year of 1909. The French Astronomical Society invited distinguished overseas observers to Meudon to conduct a series of commemorative visual observations of the Red Planet. Among them were Shiro Ebisawa (Japan), Dr. Richard McKim (future President of the BAA), from the United Kingdom, and the celebrated Italian observer, Marco Falorni, as well as a team of eight French-born observers, who enjoyed 100 clear nights out of 160 where the prodigious resolving power of the 83cm Meudon refractor was pressed into service. Many invaluable sketches of the planet were conducted during this time, in remembrance of the grand cultural tradition of visual observation conducted with such diligence in earlier decades. A similar but smaller scale program was carried out during the less favourable opposition of 1990, which yielded a further 45 detailed observations of the Red Planet.

The magnificent revolving dome erected over the historic telescope suffered terrible damage in the great storm of 1999, bringing to an abrupt end all work conducted at the observatory. But thanks to a generous grant awarded to the institution by the French Ministry of National Education, work on repairing the dome could commence, together with an ambitious program of telescope renovation. Such efforts will allow the great Meudon refractor to be enjoyed by an adoring public well into the 21st century. In the words of the late Professor A. Dollfus, “La Grande Lunettte makes people dream…..It has become legendary, an exceptional instrument symbolising a way of thinking and practicing Astronomy…. And the story is not over.”

Viva La France!

References & Further Reading

Dollfus, A. The Great Refractor of Meudon Observatory, (2013), Springer.
Sheehan, W., Planets and Perception, Telescopic Views and Interpretations, 1609-1909, (2015) University of Arizona Press; Reprint edition.
Sheehan, W. The Immortal Fire Within: The Life and Work of Edward Emerson Barnard, (2008), Cambridge University Press.


De Fideli

Tales from the Golden Age: The Life & Work of Charles Grover (1842-1921).

Charles Grover ( c 1907) at the telescope at Rousdon Observatory, Devon.

Promoted to Disability: Charles Grover ( c 1907) at the telescope at Rousdon Observatory, Devon.

                                                Dedicated to Andy Jackson (Plyscope)

Do the words of a poem lose their poignancy once its author departs this world?

Can the limp of ‘progress’ outshine the ‘grand procession’ of great accomplishment?

Can a culture, basking in the glory of its own achievement, be made mute by a faithless generation of technocrats?

Can an optical bench test inspire more than a night spent behind the eyepiece of a grand old telescope?

Let us venerate that which is deserving of veneration!

Whose crown shall we adorn with a laurel wreath?

Let us sing again of old dead men

 And clear the cobwebs from their medals.

For they have no equal in the present age

No muse to light their way.

 

 

Memory is one of humanity’s supreme endowments. Each of us acts today and hopes for tomorrow in the light of past experiences that have been woven into a life-story. When we want to know someone else, we ask that person to tell us something of the story of his or her life, for in this way personal identity is disclosed. To be a self is to have a personal history. This is what defines one’s uniqueness.

Bernhard W. Anderson : from The Living World of the Old Testament (1988).

Charles Grover faciebat

C.G faciebat

CGf.

The British Victorian era was, for the most part, the age of grand amateur astronomers – men of great personal wealth who erected large (for the time) telescopes on lavish country estates to observe the heavenly creation. But while it was certainly difficult to get on in scientific circles unless one were male and well connected, there were always exceptions, men and women with the right personal attributes – an admixture of natural curiosity, talent and diligence – who managed to break the shackles of their lowly social status, to gain the admiration of everyone, irrespective of class. Such is the story of the Englishman, Charles Grover (1842-1921).

                                                            Days of youth.

Charles was born on March 7 1842, the second son of John Grover, a shoemaker, and Eliza Benwell, a shoebinder. Misfortune struck early for Charles, when his mother died aged only 25 years, while the boy was still an infant only two months old. His father passed away when the boy had barely reached his 8th birthday. Grover’s memoirs state that he was consigned to the care of his grandmother, who lived at 37 Church Street, Chesham. Like all Victorians of lowly status, his early education was basic and often chequered. Attending the British School at Chesham, Charles received instruction in reading, writing and arithmetic, paid for by wealthy benefactors and Christian charities. And like so many impoverished Victorians, Grover supplemented his education by reciting the Holy Bible from home and reading, “with eagerness any books that came my way.” Yet it is unclear what other literature he could have gained access to. His biographer, Barbara Slater, notes that the young Grover might have benefitted from the new ‘Circulating Libraries’ and Mechanics Institutes that were being established up and down the country during the mid-19th century.

Whilst attending the British school, Grover was lucky enough to have a kindly schoolmaster, a one William Osbourne, who recognised Charles‘ latent talent for sketching and encouraged him to pursue it as best he could. But that modicum of security was to run out in 1854, when Grover’s grandmother, who acted as the boy’s guardian, passed away. It is unclear who took over the custody of the 12 year old Charles in the aftermath of his grandmother’s death, but some sources suggest that he may have been cared for by other relatives who lived in the catchment area.

What is clear is that boys of that age and social status, particularly from rural communities, more often than not ended their formal education to take up an apprenticeship. The young Charles Grover secured such an arrangement by being consigned to a local brushmaker, Henry Rose. In those days, such an apprenticeship was considered to be near the bottom of the heap of artisanal work available, but Grover accepted the position with graciousness, spending the next 15 years in Roses’ employ. During this time, Grover courted Elizabeth Birch and married her in August 1862.

Though undoubtedly Grover accepted his lot as a brushmaker, he longed for something better. In his memoirs he writes, “My mind was not in this and all my spare time was devoted to such books as I could get and the pursuit of general knowledge.”

Grover’s world changed utterly and forever in 1858 when he observed Donati’s Comet with feverish interest. Night after night, he traced its path against the background stars. On the evening of October 5, 1858, the comet passed near the bright star Arcturus in Bootes. It was at this stage that Grover committed himself to learning the constellations. On each available clear night, he would watch the stars and keep a diary of his experiences. On the night of May 8 1859, he observed a most curious phenomenon; a bright star had came very close to the Moon before disappearing behind it! Consulting an astronomical almanac, Grover discovered that the bright star was in fact the planet Saturn. It was at this stage that Grover realised that he needed a telescope.

A sketch of the appearance of Donati's Comet, as it appeared in 1858. Note it's head passing close to the bright star Arcturus and the Big Dipper asterism on the upper right.

A sketch of the appearance of Donati’s Comet as it appeared in the autumn of 1858. Note its head passing close to the bright star Arcturus, and the Big Dipper asterism on the upper right.

As one might expect, refined instruments were completely out of the question for a man of such modest means but he saved enough coin to purchase an old ship’s spyglass for the princely sum of 10/- . But where others would have soon discarded such a crude instrument, Grover embraced it with a boyish enthusiasm. “To me,” he later wrote, “ it was a wonderful instrument.” Indeed, he was to use it for two whole years, during which time, it showed him the ever-changing cadence of Jupiter’s large satellites, the battered lunar countenance with its multitudinous craters, the phases of the brilliant planet Venus and some of the brighter star clusters, most notably, the Pleiades in Taurus, as well the Beehive Cluster (Praesepe) in Cancer.

A spyglass like this launched the telescopic career of Charles Grover.

A spyglass like this launched the telescopic career of Charles Grover.

After seeing all he could with the spyglass, he sold it to raise funds for something a little better. But even the smallest achromatic telescopes of the day were prohibitively expensive. Indeed, the least expensive 2-inch achromat available at the time would have set him back £3 – a sum that represented more than a month’s salary. Undeterred, Grover resorted to making something from his own hand. After acquiring a biconvex lens of three inch aperture and five foot focus, he mounted the lens in a zinc tube and, at the other end, a crude eyepiece holder which slid along a makeshift ‘eyehole’. A modern amateur would have balked at such a contraption – which was more at home in the 18th century than the 19th- but not Charles Grover. Despite having  severe spherical and chromatic aberrations, he described its (low power) field of view as ‘brilliant’. With this instrument, Grover observed the Great Comet of 1861 and returned to the Pleiades cluster, carefully recording the positions of 52 members.

In 1862, Grover had knocked together enough funds to purchase his first ‘proper’ instrument, a 2-inch achromatic refractor of 36 inch focal length, made by the Mancunian telescope maker, J.T. Slugg & Co. The instrument was fitted with a pancratic ocular  delivering a range of magnifications of 50, 60 and 80 diameters. After testing it out, Grover proclaimed it optically excellent. Observing the Giant Planet with it, he declared:

“Though small in size this instrument performs well and the beautiful definition of its object glass cannot be surpassed. The appearance of Jupiter in this instrument with a power of 80 and a clear sky is truly beautiful, the belts and cloudy spots being seen with great clearness. Double, triple and quadruple stars are very clearly seen.”

With this new and greatly improved telescope, Grover embarked upon systematic observations of the Sun, Moon, brighter planets and the deep sky. During the 1862-3 apparition of Saturn, Grover recorded the gradual disappearance of the planet’s ring system as it came into the plane of the Earth’s orbit. In retrospect, this was a remarkable series of observations, made by such a young observer and modest instrument.

Charles Grover's darwings of Saturn during the 1862-3 apparition during which time the rings were seen as edge on.

Charles Grover’s drawings of Saturn, conducted with a 2 inch achromatic, during the 1862-3 apparition, at which time the rings were seen as edge on.

.Apart from a brief interlude corresponding to his marriage, Grover was a regular observer, making observations on each available clear night. This is all the more remarkable as he was also keeping down a full time job which often involved early starts. Grover’s new found passion for astronomy reflected a general increase in the popularity of the hobby amongst the lower and middle classes. The underlying causes for this increased interest from the lower echelons of Victorian society may have been attributed to the launching of a number of new periodicals including the Astronomical Register. By 1865, Grover had published some observations of the lunar surface as seen through his small telescope. His records soon came to the attention of more established astronomers, particularly the ‘father of all amateur astronomers,’ the Reverend Thomas W. Webb, based at Hardwicke, Gloucestershire. It was about this time also that Grover began writing to the famous astronomer and was delighted to see that Webb would write him back, encouraging the young astronomer in his studies. Indeed Grover was to often speak of Webb’s ‘kind and genial nature.’ Moreover, Webb was to the gift another 2-inch refractor (of higher pedigree) to Grover to carry on his work. Grover was to use this instrument to conduct several impressive drawings of Mars during the Winter of 1868-69.

                                               Establishing a good name

Webb evidently saw in Grover the makings of a first rate observer, and upon calling attention to his work among his distinguished friends, was soon invited to the country estate of Dr. John Lee at Hartwell house, Buckinghamshire, the well-to-do barrister and keen amateur astronomer, who had erected a magnificent 16 foot revolving dome around the 5.9 inch Tulley achromatic refractor once owned by Admiral W. H. Smyth. Grover even got a chance to look through the famous instrument having vividly recalled the beautiful view of Saturn at 240x through the telescope.

Grover was fascinated with all the accoutrements Dr. Lee had acquired to fully equip his observatory. Like a kid in a candy store, Grover recalled seeing all manner of mechanical devices – orreries both large and small, and an antique 17th century non-achromatic telescope (c. 1650) furnished with a two inch singlet lens in a 10 foot tube made of vellum. In the room annexed to the main observatory Grover noted a 3.75 inch transit telescope of five foot focus. But the device that most attracted Grover’s attention was the precision micrometer used by Admiral W. H. Smyth. Indeed, it was to inspire Grover to construct his own primitive micrometer for use with his 2-inch achromatic to carry out some double star measures. The mechanical details of this device were published in the January 1866 issue of the Intellectual Observer, to much acclaim.

Despite what some contemporary amateurs have maintained, Dr. Lee and his distinguished astronomical acquaintances were not toffs out to reaffirm their own superiority over others in society. Grover’s diaries reveal the very opposite; that of a community which rewarded observers based on merit. In his memoirs Grover noted:

The Dr. received me with the greatest kindness, made the most minute enquiries as to my circumstances, instrument, books etc, and looked carefully through my manuscript observations which I had been asked to bring for his inspection, and before I left he expressed himself as much surprised and pleased by the accuracy of the work I had accomplished with very small and limited means, made me a liberal pecuniary present and gave me a large number of books.

Grover’s visit to Hartwell House allowed him to greatly broaden his circle of astronomical acquaintances, including the famous telescope maker, George With, creator of high quality silver-on glass reflecting telescopes. Indeed With gifted Grover a fine 6.5 inch reflector for his own use. Soon he was to begin work making a suitable mount for the instrument  supervised by the Reverend Cooper Key and George Knott. Before long, Grover had made a fine equatorial mounting for the telescope, an instrument that he would use for many years to come. Such an instrument must have represented a huge leap forward for Grover, accustomed as he was to looking through small achromatic refractors. Grover’s memoirs describe his initial reaction to his 6.5 inch silver-on-glass reflector. It had, he said, ” splendid definition” and ” great light grasp.”

It was around this time that Grover began a correspondence with another instrument maker of note, John Browning, who had set up a small workshop in London, and who invited Grover to join him as his assistant. Though the salary was still modest, it was considerably better than what he was earning as a brushmaker. It was an opportunity too good to let go and so, at the age of 27 (1869), Charles, his wife and five year old son, George, moved to the ‘Big Smoke’ in search of new adventures and fortunes.

The distinguished instrument maker, John Browning(1831-1925)

The distinguished instrument maker, John Browning(1831-1925)

 

 

 

 

 

 

 

 

 

The Grovers took the move to London in their stride. No longer would Charles have to endure working for long hours on mind-numbing tasks. Now he could put his back into a job that was very much closer to his heart, assembling, testing and repairing astronomical equipment, as well as travelling the length and breadth of the country in order to aid in the proper setting up of the instruments for Browning’s extensive clientele.

In 1867, Browning had published his influential work, A Plea for Reflectors, in which he enthusiastically endorsed the new silver-on-glass Newtonian telescopes, highlighting their many advantages, not least of which was cost.

An advertisement by Browning for one of his reflecting telescopes.

An advertisement by Browning for one of his reflecting telescopes.

Browning was also a keen and well established observer of his own, possessing a first-rate 12.25 inch equatorial speculum in his own back garden in Clapham. Charles’ memoirs recount many episodes using Browning’s personal instrument.

                                                            Maturity

During much of the 1870s, Grover attended many lectures delivered by distinguished speakers in scientific circles. Indeed, Grover operated a magic lantern at many of the most prestigious meetings of the Royal Astronomical Society (RAS), giving him a ‘ringside seat,’ as it were to the scientific content therein.

After moving to more comfortable lodgings at Wellington Buildings, Chelsea, their second son was born in February 1881 but sadly died on July 13 of the same year. Curiously, his own records show that he was busy observing Tebbutt’s Comet on the very evening his second son passed away. What are we to make of this?

Doubtless some would quip that this was rather cruel, indifferent or inhumane.  It must be remembered that Grover was a man of his time and Victorian fathers were expected to rule their hearts with their heads. What is more, infant death for much of the Victorian era was only marginally (if anything) better than the child mortality rate experienced in ancient Rome. Thus, the average Victorian was much more conditioned to death than we are today. That said, I suspect Grover coped with his loss in the only way he knew how:- by getting on with things. Going onto the roof to observe might have been his way of escaping the ordeal, at least temporarily. I would like to think that a tear came to his eye, concealed in the darkness of the night, as he set up his telescope for work.

Grover’s move to London greatly increased his circle of astronomical aquaintances, which included G.B. Airy, Warren De La Rue, J.C Adams, Charles Pritchard, Richard Proctor and William Lassell. Though many of the lectures of the RAS were fascinating to Grover, he found others dull and deliberately chauvanistic, orientated more toward the upper classes. Another member of the RAS known to Grover was Captain William Noble, who, having become totally disillusioned by the pomp and ceremony of the RAS, decided to found a completely new and more inclusive society. Called the British Astronomical Association (BAA), it held its first meetings in 1890 and was open to everyone, male and female, for a modest annual fee.

                                                         New adventures

With more connections than ever before, Grover found that further opportunities knocked. And his skill in the operation of sophisticated astronomical tools meant that his services were in great demand. In 1882 Charles left Browning’s workshop to go to Australia as assistant to the young Cuthbert Peek (whose father Sir Henry Peek was a baronet and a Member of Parliament), as part of a Royal Geographical Society (RGS) expedition to observe the transit of Venus, which was due to occur on December 7 1882. Accompanying Grover and Peek on board the Liguria was Captain William Morris of the Royal Engineers and a lower ranking officer, Gunner Bailey of the Marine Artillery, Lieutenant Leonard Darwin, son of the famous naturalist, Charles Darwin, and his wife, Elizabeth.

The 45 day journey by sea to Australia was, for the most part, comfortable. The well-to-do group enjoyed first class quarters, whilst Charles had to contend with second class accommodation, a situation that made him acutely aware of his standing in the social order, but which he accepted without complaint. His new employer, Cuthbert Peek, was a gentleman through and though and never made Grover feel out of place. But the diaries of Leonard Darwin reveal a moody and ingracious disposition, constantly complaining about the bad food on board, as well as expressing a general boredom with the journey. A racist, the younger Darwin had been a prominent member of the Eugenics Society back in England, something that did him no good in retrospect, basing his ideas on his father’s bogus theory of evolution.

Peek had arranged the transport  of a fine 6.4 inch f/12  Merz refractor (pictured above), which he purchased second hand from a one Mr. Lettsom of Lower Norwood. Its relatively short focus made it a good choice for transport and Charles was already intimately familiar with its set up. Peek also brought along a small portable telescope. Grover had to make do with  a good set of high powered binoculars. As luck would have it, the crew got a chance to see a remarkable apparition – the great September Comet of 1882 – discovered by the astronomer, W.H. Finlay, at the Cape of Good Hope on September 7, just ten days before perihelion passage. Charles made copious notes while on board ship of this famous sungrazer (it came to within 1.5 degrees of the Sun). Smaller equatorial telescopes were used by Gunner Bailey, Darwin and Captain Morris.

The Liguria arrived off Melbourne on October 8, where the crew enjoyed a few days leisure, exploring the harbour and the city of the New World. Charles, as usual, recorded his experiences with copious notes, which included a visit to Melbourne Observatory, that housed an 8 inch Cooke equatorial and the centre piece of attraction; the great Melbourne Telescope; a leviathan built by Grubb of Dublin and installed in 1868, with a 50 inch mirror made of speculum metal – the last great telescope to have been fitted with a metallic mirror. The enormity of the instrument – fully five feet across and 40 feet in length- amazed everyone but especially Charles Grover.

The Great 50" Melbourne Telescope, as it appeared c 1910.

The Great 50″ Melbourne Telescope, as it appeared c 1910.

 

 

 

 

 

 

 

 

 

Mechanically excellent, the 50 inch reflector had a great name but optically it was very suspect, having poor defining power on high resolution objects like planets and globular clusters. Despite these limitations, it was reputedly a most powerful light bucket, built to continue the study of the skies of the southern hemisphere, begun by Sir John Herschel in 1847 at the Cape of Good Hope, South Africa.

From there, the expedition team set sail on the Liguria for Sydney, where Charles again had time to visit the well endowed city Observatory overlooking the harbour. A keen sketcher, Grover recorded some fine details of its two vaulted astronomical ‘cathedrals’ on the afternoon of October 18. The main instrument  was a majestic 11.3 inch equatorial refractor, erected under a dome of Munz metal (a copper alloy), its green oxide veneer gleaming in the strong, austral Sun. Another smaller dome housed a 7.5 inch Merz achromatic and several transit instruments built by the British firm, Troughton & Simms. The party were shown round by the resident astronomer, Mr. H.C. Russell, who Grover remembers with affection. Russell had already set up 3- and 4-inch refractors for the up-and-coming transit of Venus.

After enjoying a week in Sydney, Grover had to supervise the safe transfer of the delicate equipment from the Liguria to a small steam boat, the SS Katoomba, to complete the short voyage to Brisbane, arriving on the evening of October 26. From there, the RGS expeditionary team had to take a train to Macalister Government Station. Finally,  a 4-horse drawn wagon carried them the last 12 miles across a flat, grassy plain to their destination at Jimbour, on the Darling Downs of Queensland. It was now early November, a good month before the eagerly awaited celestial event.

The expedition team enjoyed fairly comfortable lodgings in a 22 roomed mansion built by wealthy colonial landowners. Mrs Darwin took it upon herself to manage the day to day running of the house at Jimbour. By the evening of November 6, Grover re-assembled the 6.4 Merz instrument upon its heavy equatorial mount and was delighted to report that not a single screw was missing and the clock drive worked as smoothly as it had done back in England. Two other huts were set up by Captain Morris and Lieutenant Darwin, which housed smaller equatorial telescopes, connected by telegraph to Sydney Observatory. By November 12, all the instruments were up-and-running and ready to go.

No time was lost carrying out night time observations and the site was deemed excellent. “We soon have striking proof of the purity of the air at this place over 1000 feet above sea level,” Grover recounted, “and it proved an ideal place for observations, only two cloudy nights occurring in the six weeks we were here.” A large catalogue of double stars were examined with the telescopes but time was set aside to look at deep sky objects too, especially the nebula around the star Eta Argus, on which Peek would write an interesting memoir upon his return to England in August 1883. The bright planets, Jupiter and Saturn, were also intensely scrutinised by the British team. Grover was especially impressed with the view of Saturn as seen through the 6.4 inch Merz. The planet, “was seen with wonderful distinctness”, he wrote, “and it is not too much to say that all that is shown of this planet on the beautiful plates of De La Rue, the drawings of the late W.R. Dawes, or the figures of the Washington observers with their great telescope were well seen with this instrument.”

The makeshift observatories soon became the centre of curiosity for the local natives, who would come by the site to peer at the ‘strange’ equipment and get a chance to observe the heavens. Peek arranged for the observatory to be opened an hour or so before sunset to allow for public viewing of Jupiter and Saturn. Usually, serious observations only commenced after local midnight and continued until the break of dawn.

Grover revealed himself to be a man of his time in his record of the aboriginal people he had encountered. Though he does refer to them as ‘blacks’ and was rather taken aback by their relative nakedness and rumours of their cannibalistic tendencies, he never denied their basic humanity.

Cuthbert Peek seen looking through the 6.4 inch Merz refractor at Jimbour, with Charles Grover assisting.

Cuthbert Peek seen looking through the 6.4 inch Merz refractor at Jimbour, with Charles Grover assisting.

As the date of the transit of Venus approached, their luck with clement weather began to run out. On the eve of the event (December 6), a bright sunny morning gave way to thick clouds, followed by thunder, lightning and heavy rain. The deluge persisted into the morning of December 7, with the result that the transit could not even be glimpsed! Throughout that depressing morning, telegrams were received from observers based in Sydney, Brisbane and Melbourne disclosing a similar tale; a large swathe of Eastern Australia was clouded out for the event. In a cruel irony however, the next morning at Jimbour was clear as gin! The sense of disappointment was especially trenchant for Darwin, who had also failed to see the transit of Venus in New Zealand in December 1874 “….. we have nothing to show for all these weeks of work,” he wrote, “there are few people who have been twice round the world to see a thing without seeing it.

                                                            Homecoming

Throughout the long journey to Australia, Grover’s wages were paid directly to his wife Elizabeth in London, as all his expenses were taken care of by Cuthbert Peek. Grover’s son, who by now had reached adulthood, had already embarked on a career as a school teacher. Grover, together with the 6.4 inch Merz equatorial, was to return to England ahead of Peek, boarding the British East India steamship HMS Merkara on the third day of January 1883. The journey, which took a route across the Indian Ocean, stopped briefly at Batavia before passing through the Suez Canal into the Mediterranean, and onward to England. Around the same time, Peek had wrote to his uncle, highly recommending Grover for a post at the family country residence in Rousdon (acquired by the Peeks in the 1870s), Devonshire, where he had entertained serious thoughts of establishing an astronomical observatory. Peek was to offer Grover a permanent position so that he might carry out further researches from the pristine, dark skies of Rousdon, a sleepy little village by the sea. It was an offer too good to pass up.

So, shortly after his arrival back in England in February 1883, Grover, accompanied by one of Peek’s men, safely transported the astronomical equipment to Rousdon, and later that year, Charles and his wife took up residence in the eastern lodge of the estate, just a short walk from where a permanent astronomical and meteorological observatory would be set up. The Grovers were to remain there for the remainder of their lives.

                                                      ‘Observer in Charge’
A makeshift, wooden observatory with a sliding roof was established at Rousdon as early as 1884, together with a simple meteorological station, but by 1885 provision was made to establish a proper observatory, made of fine teak timber, and resting on a concrete foundation. It had a properly rotating dome where the main instrument – the 6.4 inch equatorial Merz achromatic – was housed. A photographic dark room was set immediately beneath the dome, with a flight of steps connecting the two. Provision was also made to house a small transit instrument, by Troughton & Simms, of two inch aperture and two foot focal length. As well as Grover’s astronomical duties, he also made a series of meteorological readings, twice each day, and twelve hours apart – at 9am and 9pm. These included air pressure measurements, reading off dry and wet bulb thermometers, wind speed measures using an anemometer, as well as the retrieval of data from a sunshine gauge.

The Merz equatorial was outfitted with a series of eyepieces delivering powers of 64, 90, 136, 206 and 310 diameters. A Barlow lens afforded even higher powers up to 620x. A precision micrometer, by Hilger, could be coupled to the telescope for precise measurements.

Grover once remarked on the sheer elegance of the Cooke mounting for the main instrument;

A very simple and well-constructed clock movement carries the telescope with a motion so smooth and uniform that star remains for a considerable time bisected by the micrometer wire and by a regulating screw the rate can be at once made to coincide with Solar, Lunar or Sidereal time.”

The decade leading up to the dawn of the twentieth century was arguably the happiest and (certainly) the most productive years of Grover’s life. Here in this bucolic setting, far from the smog and filth of the Victorian cities, he enjoyed good health, better pay and ready access to a magnificent telescope, just a stone’s throw from his home. As well as carrying out occasional measures of double stars, as well as lunar and planetary observing, it was at Rousdon that Grover embarked on a systematic study of variable stars, inspired by a circular written by the famous American astronomer, E.C. Pickering, who actively encouraged more serious observers to take up the gauntlet.

Unlike many other kinds of astronomical observing, which can be enjoyed on a quasi-casual basis, specialising in long period variable star observing requires a concentration of will going well beyond the usual call of duty. Many hours must be dedicated to examining countless, different telescopic fields, carefully comparing the brightness of one star against other field stars and recording those observations. As a result, Grover had to memorise the appearance of many thousands of stars strewn across the heavens. In all, he completed a survey of 14,994 stellar systems with the 6.4 –inch Merz.

Though not as glamorous as the work of an astronomer who discovers a new planet or comet say, Grover’s work was routine, systematic and thorough, a far cry from the limelight – the kind of assiduity that makes possible steady advances in any sphere of human enquiry. When Charles Grover was born, scarcely 40 long period variable stars were known, but thanks to his efforts, dozens more were identified and studied, thereby contributing significantly to the grand corpus of astrophysical knowledge of our kind. He published much of his work annually, in some of the most prestigious journals of the age, including the JBAA and RAS.

Grover’s dedication to his calling was truly prodigious. His biographer, Barbara Slater notes, for example, that his diaries record observations carried out on 146 nights during 1886 (in its own right serving as some measure of the true frequency of clear skies in the UK, and in sharp contradistinction to what many contemporary amateurs may claim!!!), including 19 nights during December, where he must have endured freezing conditions for long periods of time (indeed temperatures as low as -19C were recorded in his journals!). I suspect that not many amateurs have since endured what Charles Grover did.

Like all experienced observers though, Grover’s notes reveal tantalising morsels of new insight, gained only by spending many hours at the telescope, and, often overlooked by later generations. For example, in one protracted description of the Hilger micrometer, and in connexion to double star measures he writes;

“A slide fitted with coloured glasses allows the field to be changed to red, white or blue, at pleasure, and I have found by careful experiment that the definition of certain stars is sensibly affected by the colour of light employed in their measurement.”

Could Grover have discovered that the wavelength of light can affect resolving power (or ‘defining power’ as he put it)?

Quite possibly yes! Certainly, this author knows of no earlier references to this phenomenon!

CGf c1882-95

King Solomon of old crystallised these sentiments well:

What has been will be again,
what has been done will be done again;
there is nothing new under the sun.

                                                                Ecclesiastes 1:9

We live in the shadow of our ancestors.

                                                       Old age & passing away

His employer, Sir Cuthbert Peek, died in 1901, which dealt Grover a great personal blow, as he had always held him in such high esteem. In the years after Peek’s passing, the estate was run by his son, Wilfrid. Now approaching 60 years of age, Grover’s notes reveal a growing awareness of his advancing age, but without any anxiety with the prospect of departing this world. “I never worry much about the future State,” he wrote, “for the good reason that of this we know nothing and never shall till we pass the line.

For the next ten years, Grover continued his routine work on variable stars but also obliged visitors to Rousdon with glimpses of interesting astronomical bodies though the telescope.
In 1916, tragedy struck the Grover family, when their only son, George, fell ill and died in London, aged 52. This was a time of great mourning for the British people in general. World War I had decimated the lives of so many families across Europe, rich and poor alike. Even the Peeks were not exempt from the sceptre of human conflict.

Throughout these troubled times, Charles continued to use the telescope enthusiastically, maintaining his observations whenever he could. In addition to his duties as resident astronomer at Rousdon, Grover encouraged many a young observer, writing a variety of articles for popular journals aimed at the general public. Grover’s last report on variable stars covered the year 1920 and was published by the JBAA in January 1921. On the 16th of February, Charles Grover died, just a few weeks shy of his 80th birthday.

The funeral of Charles Grover was very well attended, with a long list of obituaries. The locals came out in their droves, the Peeks included, as did many men of distinction; for he counted professors and plumbers, men of titles and commoners alike, as his friends. The Rector who conducted the funeral service was a little lost for words, as he had only known him for four years. Still he recalled Grover’s quiet faith, attending service without fail every Sunday, and always seating himself at the back of the church, far from the pulpit. Grover was buried next to Sir Cuthbert Peek, his old master, whom he faithfully served and earnestly loved.

Lizzy outlived her husband by six years and by a strange twist of fate, gave up the ghost within an hour of her master’s (Wilfrid Peek) death on October 12 1927. Shortly thereafter, the house was sold and turned into a school. The observatory too was left to fall into disrepair and was never again used for the purposes it had been built for. The famous 6.4 inch Merz equatorial now lies in the London Science Museum, preserved for the benefit of future generations.

Charles Grover reviewing his observing notes in his garden at Rousdon ( c. 1907)

Charles Grover reviewing his observing notes in his garden at Rousdon ( c. 1907)

What better way to honour a life than to continue in his footsteps? The astronomical legacy of Charles Grover inspired others to carry on the survey of the heavens. In particular, England’s latent talent for bringing forth exceptionally gifted and dedicated variable star, comet and nova hunters continued throughout the 20th century with the life and work of George Alcock (1912-2000).

Find out more:  You can read a great deal more about the life of Charles Grover by  acquiring a copy of Barbara Slater’s book, The Astronomer of Rousdon: Charles Grover (1842-1921), Steam Mill Publishing, (2005).

De Fideli

A Short Commentary on R.G Aitken’s “The Binary Stars.”

The Great Lick Refractor.

The Great Lick Refractor.

 

 

 

 

 

 

 

 

 

 

R.G. Aitken faciebat, Anno Domini 1918

 

Some biographical notes on the author:
Robert Grant Aitken (1836-1951) was born in Jackson, a small mining town in California, in the years after the gold rush. He developed a serious middle ear infection as a child, which led to his partial deafness and the use of a hearing aid for the rest of his life. The illness meant that he was unable to begin his schooling until age nine. Nonetheless his considerable academic abilities ensured that he received a reasonable school education, after which time he embarked on a journey across the American continent, where he initially had planned to study for the ministry at Williams College, Massachusetts. There his career took a new twist when he was introduced to the influential astronomer, Professor Truman H. Safford (1806-1901), who encouraged him to also study for a BA in mathematics.

After graduating, Aitken took an academic post at the University of the Pacific (San Jose) where he taught mathematics and theology to prospective undergraduates. After many years dedicated to his teaching post, Aitken began to look for another career allied to research astronomy and by 1894 soon found himself corresponding with Edward S Holden, the first Director of Research at the newly dedicated Lick Observatory atop Mount Hamiliton.

Holden agreed to take him on and in 1895, Aitken and his family took the horse drawn stage coach up Mount Hamilton. There he would begin a trial period of work as a ‘summer student’ but only after two weeks in the job was offered a longer, one year appointment. Aitken actually stayed there for a further 40 years, acting as the Observatory’s Director between 1930 to 1935.

Aitken married miss Jessie Thomas, who bore him four children, eight grandchildren and nine great-grandchildren. Shortly after enduring a nasty fall, Professor Aitken fell ill and died on October 29 1951, aged 87 years.

                                              The book and its contents

From the beginning, Aitken was set to work using the 12- and 36 inch Clark refractors to measure binary stars. At first he concentrated on confirming measures made by Burnham but soon Aitken was making discoveries of his own. Together with his colleague William J. Hussey (1862-1926), they added a 1000 new pairs to Burnham’s magnum opus; The General Catalog of Double Stars. Over his entire career, Aitken discovered 3,087 new double stars and performed measurements of 26,560 pairs!

Aitken at the telescope.

Aitken at the telescope.

 

 

Aitken’s book begins by summarising the work of his predecessors – from Ricioli in the seventeenth century to the monumental work of his illustrious colleagues – S.W Burnham et al. Indeed, the author dedicates the book to Burnham.

By this time, double star astrometry was being conducted with great diligence across the United States, in Britain and on the continent of Europe. The majority of this work was done with classical refractors of long focal length.

Magnifications employed at the 36 inch: Aitken doesn’t mention the particular types but it is assumed that either Huygenian or the achromatic Kelner models were employed. Though not used widely today, they work superbly well with instruments of f/12 relative aperture or slower. Their minimalistic design would have generated images of high contrast and good definition. The lowest working power employed with the 36 inch was 502 diameters for pairs wider than 2 arc seconds. For one arc second pairs, twice that power was found to be ideal. And for pairs of 0.5 arc seconds or less, Aitken used magnifications up to 3000 (83x per inch of aperture) to good effect.
In general, Aitken advocated the maxim; use the highest power that the seeing will permit. On lesser nights, when the air was unsteady, lower than average powers were employed.

Stopping down, diaphragms and all that:
Aitken has formed the definite opinion that stopping down the aperture is more often than not, a hindrance and not a help to the study of double stars. Stopping down was commonly used by observers such as Percival Lowell et al in the erroneous view that finer details could be made out. But while Aitken points out that some of the Lick astronomers – including Barnard and Burnham – occasionally practiced such an activity in the worst conditions, full aperture was almost invariably preferred.

Use of filters

Aitken states that coloured filters can help reduce the glare round a bright primary star making faint companions easier to pick off.

Measurements and Telescope Aperture
On page 55 Aitken reminds us that, “It is hardly necessary to add that an hour in the dome on a good night is more valuable than half a dozen hours at the desk in daylight. Everything should therefore be done to prevent loss of observing time.”

On page 63, Aitken reveals that he and other observers of double stars tended to over-estimate the separation of close pairs especially when a smaller aperture telescope was used. Comparing the micrometer measures of a statistically significant number of stars conducted with a 12-inch refractor and the great 36 inch Lick telescope reveals this trend clearly.
No of stars               Separation in the 12-inch ( “)             Separation in the 36 inch(“)
20                                                0.52                                                            0.42
25                                                0.62                                                            0.54
24                                                1.07                                                            1.03
21                                                1.38                                                            1.39

Aitken notes that this discrepancy is seen in pairs, the separations of which are less than twice the resolving power of the instruments but become negligible in wider pairs. This result was also noted over half a century earlier by the Reverend William Rutter Dawes, which he attributed to the difficulty of superimposing the micrometer wires on the swollen sizes of the Airy disks.

G.P. Bond managed to photograph and measure the wide pair Zeta Ursae Majoris (then 14.2” apart) as early as 1857 while others working with the classical refractor in other observatories had reported getting photographs of separated pairs down to an impressive 1.0″. That said, Aitken admits that such techniques have limited application over the eye in the case of sub arc second pairs – a fact that remained true until recently.

During Aitken’s day, enough data had been amassed by double star observers using various instruments of greater and lesser glory to begin to answer a fundamental question that still eludes binary star astronomers today. Can a formula be found that links the telescope’s resolving power to its aperture? For over half a century, the Dawes Limit was widely touted as the best general formula available. Specifically, it relates to a pair of sixth magnitude stars of equal brightness, and is given as 4.56″/D, where D is expressed in inches. It is noteworthy that Dawes had established this formula mainly from significantly smaller aperture instruments than those which were consummately familiar to Aitken.

In 1914, T. Lewis published a study of double star measures made by a variety of observers employing telescopes with apertures ranging from 4 to 36 inches. His results showed large variations from observer to observer but seemed to gravitate around a maximum resolution given by 4.8″/D for bright equal pairs (> magnitude 8) and 8.5″/D for faint (< 8th magnitude) equal pairs.

Upon analysis of data accumulated by Burnham, Hussey and Aitken using the 36 inch Lick refractor (see page 56), he offers the following formulae:

For bright equal pairs:  4.3″/D (mean magnitudes 6.9 to 7.1)

For equal faint pairs:  6.1″/D ( mean magnitudes 8.8-9.0).

All the Lick astronomers were able to resolve at least five systems that were as low as 0.11″ and one system -the ‘minimum for each observer’ as Aitken himself put it – as low as 0.09″. Aitken goes on to stress that they had found many equally bright pairs that were actually discovered with the 12 inch refractor and shortly thereafter measured by the larger 36 inch to have separations only 0.25″-0.2″ apart!

The resolution results with the large Clark refractors are remarkable and may well represent the limits to which a telescope can resolve given our comfortable existence at the bottom of a shallow sea of air. As a curious aside, in considering what the optimum aperture might be for visual observing, a result was obtained which puts apertures of the order of 0.75 metres (~30 inches) as near the maximum that might achieve these resolution feats.

A note on secondary spectrum and its connexion to resolution

Whatever the benefits a colour free image might be have to viewing extended objects,  it is clear from the data provided by Aitken et al with the 36-inch Lick Refractor that they were able to reach the traditional resolution limit in regard to separating double stars. This provides an interesting historical backdrop to understanding to what extent (if any) secondary spectrum (chromatic aberration) had on the efficacy of any instrument. According to contemporary received wisdom, a single number – the Chromatic Aberration (CA) index arrived at by diving the relative aperture (f ratio) of the instrument by its diameter in inches – is a ‘useful’ parameter in predicting optical performance. Here is a table showing the various CA indices for telescopes of varying f ratio and aperture.

The CA index table showing the putative efficacy of achromats of various relative aperture.

The CA index table showing the putative efficacy of achromats of various relative aperture.

The reader will note that instruments displaying a CA index less than unity are considered to have ‘unacceptable’ levels of secondary spectrum. Yet, this presents a real dilemma; the CA index for the Lick refractor (with a presumed focal length of 694 inches) is a mere 0.52, yet it was clearly able to resolve to the theoretical limit constrained by its aperture. The majority of large classical refractors from the same genre (such as the 26 inch Clark refractor at the US Naval Observatory) would fair similarly in such an analysis although  ironically they performed equally well to the 36 inch Lick.

An instructive way forward is to consider a completely different type of achromat, in particular, a 8″ f/6 rich field refractor recently put through its paces in the field for a  magazine review. This telescope has a CA index of 0.75 and thus should perform better, within the remit of its aperture, than the 36 inch Lick refractor. But this author has discovered that an 8″ f/6 achromatic is an exceedingly poor double star splitter and will not resolve pairs to its resolving limit based on its aperture alone. Specifically, in field tests, the same 8″ f/6 was unable to resolve the triple star Iota Cassiopeiae when a 80mm f/5 achromat could (as an aside, for those who have no experience with an ultra-fast 8″ lens, consider for a minute using a 4″ f/3 object glass to resolve tricky doubles)!

The explanation, in the opinion of this author, lies in the severe spherochromatism – the change in the degree of spherical aberration as a function of wavelength – inherent in even a very well executed 8″ f/6 achromatic doublet. The long focus classical refractors of old, while undoubtedly throwing up proverbial ‘gobs’ of secondary spectrum around bright objects, would have had much reduced spherochromatism at peak visual wavelengths (510-550nm) which would have allowed them to resolve pairs at or near the limit for their aperture.

In short, the CA index, as illustrated above, is simply not credible when applied to double star astrometry. The late professional double star observer, Paul Couteau, who had accrued many years of first hand experience measuring binary pairs with the large refractors at Meudon and Nice in France, suggested that much of the secondary spectrum would have been “lost in the depth of focus of these instruments”. In this capacity, an 8″ f/12 refractor (CA index 1.5) would be vastly superior to a 8″ f/6 when applied to resolving double stars. An instructive example in this regard is to to consider the superlative work by Bob Argyle, based at the Institute of Astronomy at Cambridge University, who has used the 8″ f/14 Thorowgood refractor (1864 Cooke vintage) for many years to measure pairs down to its resolving limit. Thus, caution must be exercised in ‘predicting’ optical performance based on a single figure involving f ratio and aperture. In addition, the work with these large classical achromats clearly demonstrates that better colour correction has no significant effect on resolving double stars; a fact that professional double star astronomers have clearly heeded over the decades. That conclusion also agrees with this author’s extensive experience with these instruments in the field.

The resolution of pairs as low as 0.09″ is remarkable! How can we make sense of this? One has to remember that angular resolution is wavelength dependent and, as such, could create significant inter-individual differences in acuity.

Another possibility is that the Dawes formula is in some ways too restrictive, as it pertains to equal, 6 magnitude pairs. Fainter, tight pairs, with correspondingly smaller seeing discs (and less glare) might be expected to be better resolved. The author notes that the formula 4.3″/D was established from systems at least one stellar magnitude fainter than Dawes.

Resolving power is wavelength dependent as this superlative sequence of images made by Damian Peach show.

Resolving power is wavelength dependent, as this superlative sequence of images made by Damian Peach show.

 

 

 

 

 

 

 

 

 

Chapter IV of the book delves into the mathematical analysis of the ellipse ( which need not concern us further here) and how this can be applied to establishing the true orbit of a binary star system, using the data reduction techniques available to the author in his day. Several methods of analysis are discussed, including that of Kowalsky and its modification by Glasenapp, and Zwier’s method. These techniques are then applied to a number of binary systems to illustrate how raw data can be used to establish the orbital elements. The chapter ends by taking a look at the interesting phenomenon of deducing the existence of very close, invisible companions my observing measurable perturbations in the proper motion of the star as it moves in its Galactic orbit. After discussing the first such case –  Sirius B by Friedrich W. Bessel in 1845 – Aitken briefly discusses some other  examples ‘suspected’ of having analogous companions – Beta Orionis, Zeta Cancri and 70 Ophiuchi – to name but a few.

Chapter V is written by one of Aitken’s colleagues – Dr. J.H. Moore – who discusses the phenomenon of radial velocities of stars. The history of this subject began with the development in the 19th century of the theory of wave mechanics and the exploration of phenomena associated with the Doppler effect. Imagine you are watching an ambulance approach you at speed with its siren blasting. As the sound waves are moving with their own velocity, the waves are compressed in the direction of motion, causing their frequency (pitch) to increase. Conversely, as the ambulance recedes from you, the waves are stretched out and their pitch accordingly decreases. This effect was so named after the Austrian scientist, Christian Doppler (1803-1853), who offered the first known physical explanation for the phenomenon in 1842. The hypothesis was tested and confirmed for sound waves by the Dutch scientist Christophorus Buys Ballot in 1845. Doppler correctly predicted that the phenomenon should apply to all waves, and in particular suggested that the varying colors of stars could be attributed to their motion with respect to the Earth. Specifically, pitch is to sound as colour is to light. Before this was verified, however, it was found that stellar colors were primarily due to a star’s temperature, not motion. Only later was Doppler vindicated by verified redshift observations.

The first Doppler redshift was described by French physicist Hippolyte Fizeau in 1848, who pointed to the shift in spectral lines seen in stars as being due to the Doppler effect. If the star is moving away from us, then the spectrum of Fraunhofer lines would be shifted to lower frequencies, that is, ‘redshifted’. Conversely, if the star is moving towards a stationary observer, those same spectral lines shift to higher frequencies, that is, ‘blueshifted.’

The physical quantity called red shift (z) is provided by the simple formula:
z = (Lambda (observed) – Lambda(rest))/ Lambda (rest)

Furthermore, for stars or galaxies moving at speeds much less than the speed of light, the
velocity of the star (v) can be calculated using the formula:
v = zc
where c is the speed of light in a vacuum (300 million metres per second).

Positive values of z indicate relative motion away from the observer, whilst negative z values indicate relative motion towards the observer.

The effect is sometimes called the “Doppler–Fizeau effect”. In 1868, British astronomer William Huggins was the first to determine the velocity of a star moving away from the Earth by this method. In 1871, optical redshift was confirmed when the phenomenon was observed in Fraunhofer lines using solar rotation, about 0.1 Å in the red. In 1887, Vogel and Scheiner discovered the annual Doppler effect, the yearly change in the Doppler shift of stars located near the ecliptic due to the orbital velocity of the Earth. In 1901, Aristarkh Belopolsky verified optical redshift in the laboratory using a system of rotating mirrors.

It is noteworthy that Dr. Moore still entertains the possible existence of the lumeniferous aether – a hypothetical medium through which light waves were believed to propagate. An aether of kinds seemed like a reasonable proposition at that time since all known longitudinal waves required a medium in order to propagate through space. Moore doesn’t offer a firm opinion one way or the other on this matter, but is silent on the results of a series of experiments conducted by Michelson and Morley in the 1880s and by Michelson and Miller between 1902 and 1904, all of which produced a null result for the aether.

Although all modern spectra are obtained using high resolution diffraction gratings, Moore explains that the spectrographs recorded with the large refractors employed the simpler, prismatic technique.Chapter V and VI cover quite a lot of technical detail discussing the orbits of binary stars and their geometries.  At the time of writing (1918), the orbits of 112 visual and 137 spectroscopic binaries had been determined.

In order to obtain spectra, the large refractors had to be carefully fitted with spectrometers which could accurately record the radial velocities of the components in a binary system – whether it be a visual or spectroscopic. Plate IV shows the Mill’s spectrometer attached to the 36 inch Lick refractor. The spectra were recorded photographically and this required for long, guided exposures often lasting 60 to 90 minutes  for moderately bright stars ( magnitude 5) and longer for fainter pairs. In addition, the telescope had to modified to focus the rays on the photographic plates. This required placing corrective optics (of 2.5 inches aperture) between the object glass and spectrograph, which further reduced the light gathering capability of the telescope. The reason for this is due principally to the lack of anti-reflection coatings on the glass elements and increased absorption of light by the corrective optics.

Dr Moore explains in Chapter VI that the long focus refractors were particularly well suited to the task of taking these spectra owing to their ability to naturally produce large enough image scales to measure the positions of those lines in relation to those obtained from a known laboratory source. Dr Moore explains that to accomplish this, the light from a suitable source (such as an iron arc) is made to pass over the same light path that the star takes. This acted as a so-called comparison spectrum, by which the redshifts were measured. The spectrograph had to be temperature controlled to obtain the highest quality spectra and so the Mill’s spectrometer was enclosed in a special wooden box that was lined with felt. A string of resistors were arranged along the length of the felt and were activated by a very sensitive mercury-in-glass thermostat, which kept temperatures constant to a few hundredths of a degree C throughout the night.

On page 120, Moore concedes, from practical experience, with the 36 inch refractor and the 37.5 inch silver on glass reflector in Chile, that the former is less temperature sensitive  and naturally better suited to obtaining high resolution spectra. Moore concedes that for high dispersion work (such as at H alpha wavelengths), the refractor is better suited than the reflector. For low dispersion work, the reflector is to be preferred. Since the introduction of aluminium coatings (with their near constant and high reflectance across the visible spectrum)  in 1932 however, reflectors have greatly exceeded the results of the giant refractors of yesteryear.

Although the earlier spectral classification scheme of Cardinal Secchi is mentioned in passing, Aitken adopts the Harvard Classification Scheme throughout the book, the same  basic scheme used by contemporary astronomers.

Chapter VII deals with the fascinating topic of eclipsing binary stars. Aitken mentions that Professor E.C Pickering made a detailed analysis of Algol’s light curve as early as 1880, who presumably only had access to primitive photometers. By Aitken’s time however, technology had improved considerably and on page 168, we are informed that his contemporaries could measure dips lower than 0.1 stellar magnitudes. Aitken then provides an overview of the various models developed just a few years earlier by the pioneers in this field; Henry Norris Russell and his assistant, Harlow Shapley, then at Princeton University.

Chapter VIII deals with the actual determination of stellar masses, again a matter of some technical difficulty. Aitken assumes the reader is familiar with the basic principles, citing relationships without proof. Here, we shall work through the simplest example; that of a pair of stars in circular orbits, the orbital plane of which lies along our line of sight.

Consider a system consisting of two stars seen edge on, M and N, orbiting their common centre of gravity C , at a distance x and y metres, respectively, from C.

The problem is illustrated here:

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Star N experiences a centripetal force given by Fn = NVn^2/x. Star M experiences the same centripetal force given by MVm^2/ y, where Vn = the velocity of star N about C, and Vm is the velocity of star M about the same locus, C.

But the velocity of each star can be expressed as the circumference of the orbit divided by its orbital period, p:

Vn = 2.pi.x/p and Vm = 2.pi.y/p
So squaring these expressions gives Vn^2 = 4pi^2x^2/p^2 and Vm^2 = 4.pi^2y^2/p^2
Thus, we can express the centripetal forces as
Fn = 4 pi^2 Nx/p^2 and Fm = 4pi^2My^2/p^2
By Newton’s third law we have;

Fn = Fm

Hence , we obtain Nx = My
Or N/M =y/x ( Eq1).

This important result states that the ratio of the masses in this binary system is given by the ratio of the distances of each component from the centre of mass at locus C. But we have two unknowns here, so we require another equation to solve for both stellar masses.

Let the sum of x and y be a, the linear distance between the centres of the stars.

So x + y = a
So x = a –y
And since x =My/N and y = a-x, we have x = M(a-x)/N
So M(a-x)/N = x
(Ma-Mx)/N =x
Thus x = Ma/(M+N) (Eq2)
Finally, equating the gravitational and centripetal forces
4 pi^2 Nx/p^2 = GMN/a^2
Substituting the expression for x in Eq 2 gives:

p^2 = 4pi^2 a^3/G(M+N)
So M+N = 4pi^2 a^3/Gp^2
This is one form of Kepler’s third law ( or the harmonic law as referred to by Aitken)
If we choose to express the period in years, the masses (M and N) in solar masses and the distance, a, separating their centres in astronomical units (AU), the relationship simplifies to:

M+N = a^3/p^2 ( Eq 3)

So using Equations 1 and 3 (the ratio and sum of masses, respectively), double star astronomers can work out the masses of both components.

Although we may observe the period, p, directly from measurement, we need to convert the angular separation in arc seconds, a”, so that Eq 3 is modified to:

M + N = [(a”/pi”)]^3/p^2.

Note that this is only the simplest system to analyse. In reality, astronomers are often not sure about the inclination of the orbit from our line of sight nor its eccentricity. This is discussed at great length in Chapter V and VI.

This method works well for systems whose distances are known using trigonometric parallax. But how does one come up with a way of finding the ratio of the stellar masses as shown in Eq 1? Fortunately, there is a straightforward way to do this that involves  the redshift results mentioned earlier.

Picture the pair of stars once again, orbiting the common centre of gravity (barycentre) in simple, circular orbits as before. If high resolution spectra are obtained of the two stars as they orbit the barycentre, and accounting for their natural proper motion as they orbit the Galactic centre, the astronomers would obtain a curve showing how their radial velocities change as a function of time. These will be sinusoidal curves (at least in this simple case) with different velocities but, crucially, exhibiting the same period.

From our previous considerations, we can equate the periods of both stars about the barycentre.

Thus p = 2piy/Vn = 2pix/Vm
Thus y/x = Vn/Vm

And from Eq1 we already have y/x = N/M

So, we arrive at the eminently useful result:

N/M = Vn/Vm (Eq 4).
Simply put, the ratio of the masses of the component stars of a binary system is in the same proportion to the ratio of their radial velocities about the barycentre.

Putting it all together; two relationships enabled double star astronomers to deduce the mass of both components of a binary star system. These involve their mass sums and ratios.

M + N = a^3/p^2 (where a is expressed in AU, M & N in solar masses, and p in years).
N/M = Vn/Vm.

A worked example will help firm things up.
Consider a binary system, seen along our line of sight, with a measured orbital period of 10 years and have measured radial velocities of 10 and 20 km/s. If 5 AU separates the pair, find the individual masses.

M + N = 10^3/5^2 = 40
N/M =10/20 = ½

So 2N =M and substituting this result into the first equation gives
2N + N = 40
So 3N = 40, thus N = 13.3 solar masses.
M is given by 40 – 13.3 = 26.7 solar masses.
In this way, the successful coupling of the spectrograph to the classical refractor enabled the masses of the distant binary stars to be divined.

Sums and ratios.

And the structure falls.

Man and his symbols!

Chapter VIII ends with a discussion on specific types of star. On page 219, Aitken opens up with a fascinating remark made with respect to the Cepheid variables;

The Cepheid variables entered in Table II have been omitted from the later tables because, considered as binary systems, they seem to belong to a class by themselves…..

Aitken outlines the problems in interpreting Cepheids as a type of eclipsing binary star and concedes that some astronomers had questioned whether the observed spectral line displacements were attributed to bona fide orbital motion. Certainly, no mathematical model based on binary star orbits could adequately match their observed properties, as Aitken acknowledges. That said, he asserts on page 220 that this was a minority opinion:

The majority of astronomers, however, still hold to the opinion that they are binary systems.

The regularity of the light curves of Cepheids were found to match their radial-velocity curves almost perfectly. Subsequent studies of the light amplitude of Cepheids showed typical variations between 0.5 and 2 magnitudes in visible light and velocity amplitudes in the range 30-60 km/s. The first Cepheid velocity curves were measured toward the end of the nineteenth century and at first were assumed to be the result of orbital motion. Only after more of their ‘orbits’ had been computed that it would became clear that they were physically implausible..

Aitken goes on to say that:

some astronomers have raised the question whether the observed line displacements in the spectra of these stars really indicate orbital motion in a binary system or whether they may not have their origin in physical conditions prevailing in the atmospheres of single stars.

The pulsation hypothesis gained increasing acceptance after 1910. Sir Arthur Eddington’s theoretical work from 1917 onwards showed that Cepheids are single stars that undergo radial pulsations because they function as enormous heat engines. The radial velocity curves of Cepheids represented the expansion and contraction of the star via a mechanism known as an Eddington Valve. This is caused by differences in opacity between singly and doubly ionised helium, which causes the star to undergo cyclical heating up, expansion, cooling and eventual contraction under gravity.

In calling our attention to Table XII, Aitken does show that Cepheids all appear to have later spectral types – F and G – whereas those of visual and eclipsing binaries were scattered across the entire spectral sequence; a point of interest no doubt, but Aitken does not see much significance in it.

Aitken’s belief that Cepheids were a type of eclipsing binary star might also explain why he does not mention the work of Ms. Henrietta Leavitt, who uncovered a curious relationship between the Cepheid’s absolute visual magnitude and its pulsation period. Her work was published in preliminary form as early as 1908 – fully ten years before Aitken’s book – and in more robust form in 1912. That said, it is evident that other astronomers, most notably Harlow Shapley, was using Leavitt’s discovery to develop the first standard candle to measure distances far beyond that which could be achieved (at the time) using trigonometric parallax.

The final chapters of the book  (IX, X and XI) deal quite a bit with more speculative aspects of binary and multiple star astronomy. In Chapter IX, Aitken describes what is known about some of the more famous double stars in the sky. In Chapter X, he uses tables to illustrate how the numbers of double star vary by spectral class, distance, mass distributions and so on. Aitken cautions that these data is a work in progress though, and that future surveys would show up more comprehensive statistical results. For readers who may find this kind of work of interest, this author would recommend the later book by Dr. Paul Couteau: Observing Visual Double Stars (1984), where a greater number of pairs are analysed in a similar way. These data show that over half of all stars in the Galaxy are either binary or belong to multiple star systems. It is most interesting that although measuring techniques had improved in the generation of astronomers after Aitken, the same instruments were used to make those measurements.

The subjectivity of star colours is also mentioned in passing by Aitken on page 264. In particular, he notes that Professor Louis Bell (author of the respected book on telescope optics), had noticed that when two stars of unequal magnitudes were seen close together, the fainter member was, more often than not, reported as bluish in colour and, in general, had little to do with its actual spectral class. As ever, we tend to think of these issues as being contemporaneous, but a little digging tends to show that they have their precedents in the literature of earlier generations.

The final chapter delves into the curious question of origins: specifically, how do binary and multiple star systems come into being?

Aitken briefly discusses three theories of ontogeny:

1. The capture theory: where one star captures another while passing too close to it at some time in the past.

2 The fission theory: where a single star in the process of forming divides into two or more smaller fragments, which in turn evolve into bona fide stars in their own right.

3. The fragmentation theory, which holds that  two or more fragments ‘condense out’ from a single cloud of gas and dust, and which later evolves over time to produce a new binary or multiple star system.

Aitken concedes that all of these theories have merit  and discusses the astronomers who originated these models. Suffice it to say that the chapter makes for fascinating reading in the 21st century!

What the book means to double star observers in the 21st century;nothing new under the Sun!

The determination of the orbital elements of binary stars involves quite a bit of mathematical analysis. But unlike today, the professional astronomers of yesteryear, together with their assistants, had to make do with primitive calculating machines, slide rules and the like, in order to carry out their complex calculations. Today, computer programs make much lighter work of this.

A question for modern graduate students: can you follow the mathematics covered in this book?

We have seen how the classical refractor reached the theoretical limit of its resolving power, even in the larger apertures. Despite the advent of more exotic types of glass (short flints and the like) in the early twentieth century,  the astronomers did not feel the need to upgrade them in any way. Self evidently, this would have been overkill; cheap and cheerful crown & flint was more than up to the task. For example, why haven’t the double star astronomers using the 26 inch Clark at the US Naval Observatory ‘upgraded’ the object glass with FPL 51 or FPL 53 or some such?

Because it is not necessary to do so!

The current obsession with small apochromatic refractors is entirely an amateur phenomenon; a solution looking for a problem.

The work described by Aitken in this book should provide a lot of encouragement to those who wish to take up the fascinating hobby of double star observing. If the large classical achromats could reach their resolution limits, so too can their modern equivalents, especially in the smaller apertures available on today’s market. These days, small achromatic refractors are available for very little money and other (equally ergonomic) designs show great promise even in larger apertures e.g, the Maksutov and Schmidt Cassegrains, as well as the venerable Newtonian reflector (preferably f/6 or slower).

Last but not least, the work described in this book reminds us that no matter how well informed we think we are today, our forebears never ceased to come up with ingenious solutions and amazing surprises.

They too were people, just like you and I.

We can still learn something from them today.

Nota bene:

A 1919 review of the Binary Stars

A 2007 review of the same text.

De Fideli

The Dubious Career of Leo Brenner.

Spiridion Gopchevic aka Leo Brenner (1855-1926?)

Spiridion Gopchevic a.k.a. Leo Brenner (1855-1926?)

We do love our scoundrels!

To get ahead in astronomy it takes dedication and truthfulness in equal measure. Unfortunately, Leo Brenner( 1855-1926?) had neither.

Here was a man who’s whole life was a lie. Brenner’s father was a wealthy ship owner and merchant based in Trieste (then administered by Austria), but his business went bankrupt. Still, Brenner wished the world to believe otherwise, claiming (falsely) that he was a Count and descended from the ancient kings of Serbia. Brenner – a high-school drop-out – married a very wealthy lady and suddenly took a fancy to astronomy in his thirties. In a bid to outclass his learned peers, Brenner built a lavishly equipped observatory with a first-rate 7-inch refractor (made by the prestigious makers, Reinfelder & Hertel) in 1895 at his villa in Manora, overlooking 20 acres of picturesque gardens. He then bought up the finest astronomical books of his age – 4,000 volumes in all – storing them in a grand library annexed to the observatory.

He looked the part.

It was here that he suddenly came to the fore as an ‘authority’ on some of the most contentious astronomical issues of the day. And for a while he fooled everyone; great and good alike. But as time progressed, and his publications became ever bolder, more incredible and more voluminous, the community began to see through him.

Where Percival Lowell in the New World saw a few dozen canals on the Martian surface, Brenner recorded no less than 164! Indeed, Brenner claimed to have seen 34 such canals with only a 3-inch glass! In 1897, he reported micrometric measures of Sirius B even though the great double star astronomers of the day – S.W Burnham and the like – reported that it was, at that time, hopelessly lost in the glare of the Dog Star!

The grand 7-inch Reinfeld & Hertel refractor used by Brenner at Manora Observatory.

The grand 7-inch Reinfeld & Hertel refractor used by Brenner at Manora Observatory.

An honourable scoundrel would have retreated quietly from the limelight, perhaps gaining some more experience at the telescope before moving on. But that wasn’t Brenner’s style. When confronted about these and other issues, he viciously turned on his critics to reveal more of his true character. He upset a lot of people. For example, when Lowell expressed his disagreement with Brenner over his (erroneous) claim of a 24-hour rotation period for Venus, he spent the next few years publicly humiliating his erstwhile hero. Indeed, anyone who as much as raised a sceptical eyebrow in the astronomical literature regarding Brenner’s ‘work’, became his mortal enemy. Soon, he hadn’t a good word to say about anyone.

One of Brenner's Martian maps displaying a riot of canals.

One of Brenner’s Martian maps displaying a riot of canals.

 

 

 

Eventually, the editors of the various journals Brenner (whose real name was Spiridion Gopchevic) contributed to flatly refused to publish any more of his observations. Thick skinned, his reaction was to launch his very own journal and fill it with his own fictitious observations. It even featured ‘contributions’ from some of the most respected astronomers of the day – E.E. Barnard to name but one – but these too were faked, no doubt in a desperate attempt to maintain his ‘prestige.’ Most telling of all though is that Brenner became disillusioned with astronomy almost as quickly as he had gained an interest in it. He sold his grand telescope at Manora and all its auxiliary equipment.

It was all over by 1909.

Brenner’s rather tragic life holds water for us today. You see, you can’t buy yourself a reputation in astronomy; it can only be earned. There is no App for true experience, and no place for foul play. Cheat and you’ll be found out!

More on Leo Brenner here.

De Fideli

The Telescopes of the Reverend Thomas William Webb

TWWebb

 

 

 

 

 

 

 

 

 

 

 

 

Working for work’s sake, and that from the highest motives.

T.H.E.C. Epsin

 

Brief Biographical Details:

Thomas William Webb was born on the 14th day of December 1806 (it is noteworthy that in Reverend Epsin’s A Reminiscence, in the introductory pages of Celestial Objects for Common Telescopes [1962] his birthday is quoted as December 14, 1807), in the county of Hereford, England, one of two children to his parents, the Reverend John & Sarah Webb. The elder child, a girl, Anne Frances (born 1801) died tragically when Thomas was just a few years old and thereafter remained an only child. Thomas’ mother, who had long struggled with mental and physical illness, was unable to provide the usual maternal guidance to her son. Some sources state that she died when Thomas was just a boy, but in fact she survived to see her son marry and finally gave up the ghost in July 1849. It is difficult to gauge how Thomas dealt with his mother’s mental health issues. Perhaps the pain he felt made him somewhat upset or ashamed (a typical Victorian attitude), thus explaining why he rarely spoke about her. Breaking with the tradition of the time, young Thomas was home schooled by his father, together with a few other children from the local gentry, who instilled in him a great and abiding reverence for the workings of the natural world. His was a classical education; mastering mathematics, the natural sciences, ancient history, Latin, German, French and even some Hebrew. Such an upbringing made him a prolific maker of notes, preternaturally curious and studious – attributes clearly in evidence from the voluminous literature he left behind to posterity(1).

In 1826, Thomas entered Magdalene College, Oxford, reading mathematics for which he received a second class honours degree in 1829. Whilst at Oxford, he also studied divinity and was ordained an Anglican minister in the same year. In 1843, he married Henrietta Montague, a woman he later described as “having rare gifts and a most generous heart”. The marriage was a happy one but sadly, childless. Henrietta died of apoplexy (a stroke) on September 7, 1884, which dealt him a severe blow. The following year, his health failing rapidly, the Reverend T.W Webb passed away on May 19.

Early Days with the Telescope
Webb’s first recorded astronomical observation was of a meteor made on January 5, 1818(1), when he was just eleven years old. Just a few weeks later, he made observations of the Moon with telescopic aid. What is clear is that Webb had access to small astronomical telescopes, lent to him by friends of the family. The first identified telescope used by Webb was a small 1.3 inch refractor by Bates, which he made use of in the early 1820s. But by this time, he was dabbling in making his own optical devices, mostly small speculum metal mirrors of 3-6 inches in aperture. Though he endured many failures in casting good metal specula, he finally achieved success in 1827, where his diary dated September 9, showed that he had managed to make “a small Newtonian with fixed specula and eyepiece… extremely satisfactory and immensely improved, seemed to bear a power of 60 or 70.”

Over the coming months, he was able to make further improvements to the instrument, finally exclaiming with some excitement on August 23, 1828 that. “….my telescope is a superior one by Herschel’s own tests!!!

The 1820s marked a crossroad in astronomical instrumentation. The achromatic refractor, employing a doublet objective of crown and flint glasses was, with very rare and notable exceptions, confined to small aperture telescopes (rarely in excess of 4-inches) because of the difficulty of obtaining sufficiently high quality glass blanks that were free from bubbles and striae. This led to vigorous researches into devising other means of overcoming these technological problems. Two avenues of research were pursued; the dialyte and the fluid lens. In the late 1820s, A. Rogers (2) proposed using a full sized Crown singlet coupled to a smaller piece of flint glass placed well back in the focal plane, with the result that adequate achromatism could be obtained. Rogers managed to couple a 3 inch flint lens retro-focally with a 9 inch Crown object glass of 14 foot focus. Around about the same time, other amateur astronomers considered using liquid lenses. Organic fluids such as carbon disulphide were deemed particularly suitable, owing to their perfect transparency, relative stability and high refractive index. Webb actually built and used a telescope with a liquid lens for four years between 1830 and 1834 and to good effect.

Neither the dialytic or the liquid lens refractors achieved much in the way of popularity though. In much more recent times, the British inventor, John Wall (the as yet poorly acknowledged inventor of the Crayford focuser), managed to construct a 30-inch dialyte (3). Intriguingly, in recent times, there has been renewed interest in the construction of liquid lenses. See here for more information.

Webb’s ‘Common Telescope’; the 3.7 inch Tulley Refractor
In the summer of 1834, Webb’s father purchased a ‘capital telescope‘ for his son built by the younger Tulley, with a 3.7 inch  doublet object glass and a focal length of five feet ( f/16). The instrument duly arrived on July 3 and by July 22, Webb had subjected it to “a thorough trial, to do which I sat up, & knelt down in the gravel path till past 1. The result was most and completely unexpectedly satisfactory….. for very little did I think I had got a first rate instrument when I received it.” (1)

Remarkably, this telescope was to be Webb’s main instrument for the next 24 years and served as the ‘common telescope’ which he used to compile his now universally lauded Celestial Objects, first published in the same year as Charles Darwin’s  Origins (1859). Using his Tulley achromatic, Webb carried out unsystematic observations of the solar photosphere, the Moon and the major planets, double, multiple and variable stars, as well as the brighter deep sky objects.

A small Tulley refractor from the mid 19th century.

A small Tulley refractor from the mid 19th century.

Ever since 1844, Webb had been enthralled by Admiral W.H Smyth’s A Cycle of the Celestial Objects, a masterful survey of the night sky conducted with a substantially larger (and not at all common for the era) 5.9 inch refractor also by Tulley. Although Webb openly acknowledged the greater suitability of Smyth’s Cycles to the most advanced amateurs, he (correctly) surmised that his work would be better served by what could be achieved with a smaller telescope.

We can glean some information on the optical performance of the 3.7 inch Tulley refractor by exploring how well it performed on double stars he observed in compiling his Celestial Objects. The Dawes limit (expressed in seconds of arc) for such an instrument is 4.56/D, where D is the diameter of the object glass (in inches). This yields 1.23”. Double star astronomer, R.W. Argyle, based at the University of Cambridge, found that Webb was able to observe that Zeta Cancri and Sigma 1517 Leonis were slightly elongated (both 1.0” splits in 1849 and 1851, respectively), whilst Sigma Canis Majoris had ‘discs in contact’ (1.3” in 1856). These data indicate that the Tulley refractor Webb used for nearly a quarter of a century was operating at or very near its theoretical resolving power.

The 3.5 inch Triplet Dollond Achromatic
Apart from the instruments which he owned outright, Webb lived at a time where there was a culture of sharing instruments among a large circle of friends and astronomical acquaintances. We know that Webb also borrowed at least one other instrument – a 3.5 inch Dollond refractor with a triplet objective. First constructed back in 1771, it had a focal length of 44.5 inches (relative aperture 12.7) and was purchased by William Wollaston, who  then passed it down to his son, William Hyde Wollaston. In turn, the younger Wollaston bequeathed the instrument to the Astronomical Society of London (later the Royal Astronomical Society) in 1828. Wollaston stipulated that the instrument should not gather dust but be lent to ‘some industrious member’.

Wollaston achieved his aims and the instrument was used by a succession of observers, finally arriving at Hardwicke (then Webb’s parish and place of residence) in 1856. It is difficult to see how the 3.5” Dollond would be of any advantage to him over his (larger) Tulley refractor. Indeed, he later expressed some degree of ambivalence about the same telescope. In a letter dated January 5 1857 to the secretary of the RAS, Webb said of the Dollond triplet, “I cannot pronounce it first rate” but later said in his notes that the same instrument was “very fine against my Tulley, and though there is no very wide discrepancy, I think mine beats it.”

It may be of interest to the reader that the self-same Dollond triplet was subjected to a more thorough optical assessment by the famous British optician, Horace E. Dall, in 1980. His report showed that the instrument had a few small errors mainly related to stress- induced astigmatism owing to slight warping of the lens elements arising from over-tight mounting. The instrument is now exhibited in the Science Museum, South Kensington, London.

While one might expect an observer that became so intimately acquainted with the a small achromatic refractor, using it regularly over the course of nearly a quarter of a century, might have held onto it for sentimental purposes, we learn that in January 1858 Webb sold his Tulley, making temporary use of a smaller refractor by Bardou, which belonged to his wife, Henrietta, and which had an aperture of just 2.2 inches and a focal length of 27.8 inches. But a few months later, Webb took delivery – no doubt on the recommendation of his friend, the Reverend William Rutter Dawes – of a 5.5” object glass of 7 foot focus made by the talented American telescope maker, Alvan Clark of Cambridge, Massachusetts.

After it finally arrived in June of 1858, Webb employed some workmen in Birmingham to make a tube for it but having seen their shoddy workmanship, sent it back to them. By September of that year, he had made his own makeshift tube to assess the quality of the American object glass:

First Trial of the Great Object Glass by Alvan Clark, 5.5 inches clear aperture, fitted up temporarily in an old square deal tube. Its performance, in the utter absence of centering, appeared to be admirable.

In another note made in 1859 he claims that having examined the images of Zeta Cancri through Admiral W.H Smyth’s 5.9 inch Tulley refractor, Webb judged this famous instrument to ‘appear inferior to my own’ [Clark] (1).

A year passed but Webb still did not secure a suitable tube to mount the Clark object glass. Why he didn’t is somewhat of a mystery. Perhaps he was having second thoughts about dealing with such a large and cumbersome telescope? In addition, the optical tube would have required a very substantial mount. We see other clues as to why Webb delayed resolving these problems. The great telescopist always observed in the open air and from the serenity of his own garden. He never had an observatory like many of his gentleman astronomer chums. Perhaps he found that a long focus 5.5 inch Clark might simply have been too large and unwieldy an instrument to use regularly in the field?

J.C.D Marsh(1) offers us further insight;
Webb was certainly aware of the micrometric work being carried out by Dawes, Smyth and others, and he would certainly have been able to afford a large telescope and micrometer had he so wished.

Marsh goes on to cite other reasons for his avoidance of that particular modus operandi, including the demands of his clerical duties and his deteriorating eyesight owing to advancing age. But this author suggests that it was the ‘general’ or ‘non-specialised’ nature of his observing practices – wandering from the endless delights of the Moon to a bright planet and onwards to an auspicious cometary interloper, and from there to the far distant stars – that might have given him pause to follow the paths of his closest astronomical acquaintances. Compared with many of his peers, Webb was a ‘jack of all trades’ observer, uncommitted to any particular astronomical ‘cause.’ His was a spirit more than happy to get ‘lost’ in the glories his little telescope presented to him. For example, take this excerpt from the section on Cygnus in his Celestial Objects;

I had at one time conducted a survey of the wonders of this region with a sweeping power, but want of leisure, an unsuitable mounting, and the astonishing profusion of magnificence, combined to render this task hopeless for me, which, I trust, may be carried through by some future observer.

Whatever the reasons, we do know that Webb‘s interest in refractors waned somewhat as he heard word of new technology that was sweeping the British amateur community during the 1860s. Still, Webb made use of his ‘makeshift ‘ Clark achromatic, observing a variety of objects, including the exploration of the Great Comet of 1861 (1861 J1), where his surviving drawings show clear evidence of jets and dust shells reminiscent of recent comet apparitions, such as Hale-Bopp or Hyakutake.

Ever since the first reflecting telescopes were made in the late seventeenth century, astronomers had used speculum metal (an alloy of mostly copper and tin) for their mirrors. But these had many issues. For one thing, metal is difficult to grind and figure into the required parabolic shape necessary to get the best images. It had a reflectivity of only 68 per cent at 450nm (blue) rising to 78 per cent at 650nm (red). However, when exposed to the elements, it tarnished rather quickly, losing an estimated 10 per cent after just six months in the damp British air (5). Removing the mirror for polishing also changed its figure, requiring a complete regrinding of its surface. Furthermore, because of the high density of speculum, even fairly small mirrors were very heavy and cumbersome to mount.

All these issues impelled a number of scientists to redouble their efforts to look for better ways of making telescope mirrors and, accordingly, experiments were set up to establish whether substances like silver could be deposited onto glass substrates. In 1855, the great German chemist, Justus von Liebig, produced metallic surfaces refined enough to use in optical devices but never applied it directly to telescope mirrors. Within a year of Liebig’s findings though, C.A. von Steinheil in Germany and Leon Foucault in Paris had independently demonstrated that silver could be deposited on a pre-figured glass substrate, the latter producing a fine speculum some 20 inches across. This was the game changer astronomers had wished for, because it suddenly made available large glass-based primary mirrors that maintained their reflectivity longer and could easily be re-silvered and polished as and when required. What’s more, because these silver-on glass mirrors were much cheaper than the lens-based object glasses that dominated until then, many more amateurs could afford to acquire them.

By 1859, the British amateur astronomer, Reverend Henry Cooper Key, succeeded in fashioning a fine 12 inch f/10 mirror and shortly afterwards produced an 18.25 silver-on -glass mirror with a focal length of 11 feet. After publishing his methods, Key’s work came to the attention of George With (1827-1904), who managed to make four such mirrors ranging in aperture between 5 and 6.5 inches. With also corresponded with Webb and supplied him with a 5.5 inch silver-on-glass mirror that he subjected to tests.

In August 1863, Webb wrote to the secretary of the RAS informing him that he had, “a 5.5 inch silvered Newtonian on trial… and it does its duty well. I think it must be fairly equal to a 4-inch achromatic or more & he will yet, I am persuaded, do better yet.”

Soon after, another British mirror maker came to the fore – a young George Calver (1834-1927)(6). Calver’s appetite for astronomy was whet after his local vicar, the Reverend Matthews of Great Yarmouth, showed him some of the splendours of the heavens through his newly acquired silver-on-glass reflector with a mirror supplied by With (6). Matthews is said to have set a challenge to Calver to see if he could make a mirror as good as the one he had in his possession. Luckily, Calver accepted the challenge and soon found him-self hard at work, fashioning, gifting and selling his own specula. England now had three choice mirror makers and amateur astronomy across the country flourished. A quiet revolution was underway.

In 1864, Webb purchased a 8-inch mirror from With but there are not many surviving records of him using it. However, in 1866, Webb’s father (then aged 90) bought a larger telescope for his only son; a 9.25 inch f/8 Newtonian reflector on an ‘equestrian’ mount manufactured by the Reverend Edward Lyell Berthon (1813-99). This was to be Webb’s final and largest telescope that he would use regularly for the last two decades of his life.

Webb's 8 inch Newtonian with optics made by George With. Image credit: D Buczynski.

Webb’s 8 inch Newtonian with optics made by George With. Image credit: D Buczynski.

Owing to the large size and massive mounting of the With/Berthon Newtonian, Webb was compelled to change his observing habits; no longer could he observe in the open air freely, like he had done for decades. He would have to build an observatory of sorts for his new instrument. With a large number of astronomical friends and acquaintances to call upon, Webb had many architectural genres to choose from. He could lavish huge sums on a brazen, domed observatory, like those erected by the Reverend Dawes at Haddenham, Buckinghamshire, or the tycoon, George Bishop, in the Inner Circle of Regent’s Park, London.

The observatory of George Bishop ( c 1850) housing a 7-inch Dollond refractor.

The observatory of George Bishop ( c 1850) housing a 7-inch Dollond refractor.

Instead he went for the much more economical Romsey type observatory (shown below), so named because it was first devised by E.L Berthon in his home parish of Romsey and was constructed relatively cheaply and quickly from wood, with a rotating canvas roof. It was situated a few yards south-southeast of the vicarage and served its purpose perfectly well for over 15 years when it began to show its age all too easily. In a letter to Arthur Ranyard, dated 2 February 1883, Webb confessed:

My telescope roof is all to pieces. I’ll put on another roof with two pairs of opposite shutters, not only saving time in turning, but as the one side rises more steeply than the other, giving relief in position where now it cramps the head awkwardly. There was a bright thought.

Denis Buczynski inspects the With/Berthon reflector ( BAA# 83) at his home in Lancaster.

Denis Buczynski inspects the With/Berthon reflector ( BAA# 83) at his home in Lancaster. Image credit: D. Buczynski.

 

A 'Romsey type' observatory. Image credit: D. Buczynski.

A ‘Romsey type’ observatory. Image credit: D. Buczynski.

 

 

 

 

 

 

 

 

 

 

 

 

 

The optical quality of his 9.25 inch With-Berthon reflector was undoubtedly excellent, as judged by the many exquisite drawings of the moon and planets he left behind in his notebooks. Webb achieved a clean split of Eta Coronae Borealis, which, at the time, had a separation of 0.55” -satisfyingly close to the Dawes limit for such an aperture (0.5”). In addition, his 9.25 inch speculum resolved Gamma 2 Andromedae at powers of 225x. Webb also reported seeing marked elongation in Omega Leonis (0.52″ in 1878). This provides further evidence that when properly executed, Newtonian reflectors can be very effective double star splitters (at least for near equal magnitude pairs). This also dovetails well with this author’s ongoing observations with a modern 8” f/6 Newtonian.

Webb discovered 10 new double and multiple stars mostly with his 9.25 inch reflector, its considerable light gathering power doing especially well with wide and faint companions. He did not conduct measurements on these systems, leaving that delicate work to more specialised double star observers, such as S.W Burnham, W.R Dawes and Baron Dembowski, who employed large and well mounted refractors.

Veteran BAA member, Denis Buczynski, informed me about the telescope’s history after Webb passed away:

“Webb was a friend of George With,” he explained, “and I am sure he sky tested mirrors for With. Webb used a 9 inch f/8 on a Berthon Equatorial, an unusual mount. The BAA mount was not a commercially produced mount, it was a one off. It was a cast iron pedestal tilted to accept a polar disc (this disc was made of slate covered by a circular sheet of brass), containing four brass rollers and the half circle which held the declination circle. The declination axis was in the plane of the polar disc above two of the rollers and held two curved arms which connected to the tube and also supported the steady rods. The mirror was definitely a With and was signed by him accompanied by a Latin inscription [Withus Herefordensis me ad astra investiganda fecit(1)]. The only commercial mounts sold as Berthon mounts were made by Horne and Thornthwaite. The BAA mount was not one of them. I asked Horace Dall about the small discrepancy between the two sizes Webb had quoted for his telescope (9.25 and 9.25 inches) but he did not consider it significant. He said the quoted aperture was sometimes measured from the very edge of the mirror and sometimes from the interior of the edge chamfer. Also it was possible that Webb had in his possession more than one 9 inch mirror from With. After Webb’s death, his instruments were passed onto the Reverend T Espin (who edited later editions of the Celestial Objects) at Tow Law, near Durham. After Espin’s death in 1935, the observatory at Tow Law continued to be operated by William Milburn who was Espin’s assistant. In 1938 Milburn offered the Webb 9 inch for sale in an advert in the JBAA. The BAA accepted the donation of instrument 83 in the late 1940’s from Charles Waller. It is very possible that Waller had purchased the 9 inch from Tow Law and then it was eventually donated to the BAA ten years later. The link between Tow Law and Waller is the only link needed to firmly establish that BAA instrument number 83 was the 9 inch With reflector used by Webb.”

An edge-on Saturn as drawn by D. Buczynskusing Wbb's 9 .25 inch speculum. Image credit: D. Buczynski.

An edge-on Saturn as drawn by D. Buczynskusing Wbb’s 9 .25 inch speculum. Image credit: D. Buczynski.

In the late 1970s and early 1980s, Buczynski used Webb’s With/Berthon as his main lunar and planetary telescope, having had both mirrors re-aluminised. He was kind enough to provide some drawings he made through it (shown below). He also confirmed that the optical figure on the mirror was first rate [as was another 18 inch With mirror tested by Buczynski and used by Nathaniel Green(8)].

Jove as recorded by D. Buczynski using Webb's large Newtonian. Image credit: D. Buczynski.

Jove as recorded by D. Buczynski using Webb’s large Newtonian. Image credit: D. Buczynski.

 

Mars as observed by . Buczynski using Webb's large newtonian. Iage credit: D. Buczynski.

Mars as observed by  Buczynski using Webb’s large Newtonian. Image credit: D. Buczynski.

There are some subtle differences between the images used in modern Newtonian reflectors that employ aluminium as compared with their silvered counterparts. This is best illustrated by means of a graph showing how the reflectance varies with wavelength (see Figure 1). Specifically, silver absorbs blue wavelengths much more strongly than Aluminium. Thus, objects would be appear slightly red enhanced in the silver-on-glass reflector, whilst modern aluminium coated mirrors would be better colour balanced (perfectly achromatic).

Figure 1: showing the reflectance of silver, aluminium and gold as a function of wavelength.

Figure 1: showing the reflectance of Silver (Ag), Aluminium (Al) and Gold (Au) as a function of wavelength.

 

 

 

 

 

 

 

 

 

 

That said, Webb considered his reflector essentially achromatic. In his discussion on telescopes in Volume One of his Celestial Objects, he seems to have grown more partial to the images produced by his specula:

An achromatic, notwithstanding the derivation of its name, will show colour under high powers where there is much contrast of light and darkness. This ‘outstanding’ or uncorrected colour results from the want of a perfect balance between the optical properties of the two kinds of glass of which the object glass is constructed; it cannot be entirely remedied, but it ought not to be obtrusive……… Reflectors are delightfully exempt from this effect; and as now made with specula of silvered glass, well deserve, from their comparative cheapness, combined with admirable defining power, to regain much of the preference which has of late years been accorded to achromatics.

According to science historian, Thomas Hockey(4), based at the University of Northern Iowa, Webb entered into a long standing debate concerning the perceived colours evident in the massive Jovian atmosphere. Specifically, one issue raised was the relative fidelity of the Jovian image garnered in achromatic refractors compared with those derived from the then (relatively) novel silver-on-glass reflectors. Blue light is led astray in the achromatic doublet but was absorbed by the silver and has an ‘overabundance’ of red.

But which was worse?

Webb finally came out on the side of the reflector,” writes Hockey, “which, at least, eliminated the blue altogether, rather than producing an annoying blue fringe.”(4)

A brief Commentary on Webb’s notes: The Christian Apologist
As was the custom of observers of his age (and which, sadly, has much declined in the modern era), note keeping was an integral part of observing culture. A note-maker became a man or woman of letters. His observational books and other writings are laconic and factual, containing maxims, often expressed in correct Latin (in contrast to some examples of Admiral W.H Smyth’s use of the Roman language in his Cycles). Webb paid very close attention to his observing conditions, his writing neat and tidy.  Unlike many other observers, Webb had a fondness for observing star fields; indeed he thought of these as new objects in their own right. He would observe on a Sunday. His notes were most often brief, well structured, and not without a sense of humour. Webb published many of his finest works in Nature, its founder and first editor, a one Sir Norman Lockyer, rewarding the diligence of his long-time friend.

Throughout his writings we gain many glimpses of his sincerely expressed reverence for the universe around him. For Webb, this reverence did not upwell from any deep understanding of the objects he visited with his garden telescopes. After all, the nature of the many nebulae he observed was not known at the time. Rather, that same reverence was derived from a trenchant sense of ignorance concerning the objects his eyes met with.

Albert Einstein put it well when he said:

The most beautiful thing we can experience is the mysterious!

Despite the growing power of scientific naturalism within later Victorian society, Webb couched everything, with firmness and  gentleness, in terms of the Biblical God he knew existed. Seen in this light, his astronomical writings, his devotion to exploring the wonders of Creation with his telescopes, were more like prayers than anything else.

What T.W. Webb’s Legacy Means for us Today

Phil Jaworek's cool Towa Model # 339 upgrade. Image Credit: Phil Jaworek.

An excellent yet inexpensive Towa Model # 339 upgrade. Image Credit: Phil Jaworek.

 

Elisabeta Regina. A more expensive but more ornate 80mm f/15 achromat.

Elisabeta Regina. A more expensive but more ornate 80mm f/15 achromat.

 

Octavius: the author's economical 8" f/6 reflector on a Dobsonian mount.

Octavius: the author’s economical 8″ f/6 reflector on a Dobsonian mount.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In the early 21st century, obtaining telescopes like those used by Webb is not difficult, nor necessarily expensive. What Webb’s legacy has shown us is that the kind of telescope you choose is far less important than what kind of observer you ultimately become. Webb’s small refractors, which he used profitably for nearly a quarter of a century, would optically be similar (or inferior) to a modern long focus achromatic. One can choose from an economical model or one that is more ornate. The same is true for Webb’s large Newtonian reflectors. The telescope maketh the man. Choose your telescope, carve your path through the starry wilderness and create your own legacy “til the dappled dawn doth rise.” (1)

References
1. Robinson, J. & M., The Stargazer of Hardwicke; the Life and Work of Thomas William Webb, Gracewing, (2006)
2. Rogers, A. On the Construction of Large Achromatic Telescopes, M.N.R.A.S 1 (1827), 71.
3. Wall, J. Building a 30-inch Refractor, J.B.A.A. 112 (2002), 260.
4. Hockey, T., Galileo’s Planet: Observing Jupiter Before Photography, Institute of Physics Publishing, (1999).
5. http://iopscience.iop.org/0950-7671/24/9/308/pdf/0950-7671_24_9_308.pdf
6. http://www.oasi.org.uk/History/Calver.shtml
7. Webb, T.W., Celestial Objects for Common Telescopes Vol One and Two, Dover, (1962).
8. Nathaniel Green life and works

 

My sincere thanks to Denis Buczynski for providing some of the images in this essay, as well as sharing some invaluable insights into Webb’s large reflecting telescope.
Find out more about the life and work of T.W Webb in our up-and-coming book, Tales from the Golden Age of Astronomy.

                                                                                                        De Fideli                                     

 

 

The Life & Work of Dr. William Doberck (1852-1941)

The Makree refractor erected in Hong Kong.

The 13.3 inch Markree refractor erected in Hong Kong.

It gives me great pleasure to present an essay written by my compatriot, Dr. Kevin MacKeown (now at the Unversity of Hong Kong) on the life and work of the Danish astronomer, Dr. William Doberck (1852-1941), who, amongst other things, dedicated his professional career to double star astrometry.

Dr. William Doberck ( 1852-1951).

Dr. William Doberck ( 1852-1941).

Most significant for me was his spell at Markree Observatory, Co. Sligo, Ireland (my homeland), where he used a magnificent 13.3 inch refractor, with a lens fashioned by Robert A. Cauchoix of Paris, which was privately owned by a wealthy British gentleman, Edward J. Cooper. There the telescope was used to catalog 60,000 stars. After leaving the west of Ireland, Doberck moved the telescope to Hong Kong Observatory, where he served as its first director between 1883 and 1907.

You can view this essay here.

 

Neil English is working on a new book – Tales from the Golden Age – honouring the life and work of the greatest telescopic observers in history.

De Fideli.