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