Observing the Super Blood Wolf Moon.

Keeping it simple for the January 2019 Lunar Eclipse.

 

Date: January 21 2019

Time: 00:05UT

Yeehaw! The skies have remained clear this evening and things are looking great for tonight’s total lunar eclipse. What a difference that makes to the total washout we had here for the last one, which occurred on the evening of July 27 2018!

Okeydokey. What exactly is a Super Blood Wolf Moon?

It’s a Super Moon because the event occurs when the Moon is significantly closer to us than normal, making our natural satellite bigger and brighter than at other times.

It will be a Wolf Moon as it simply denotes a full Moon in January. The connection with wolves is a little harder to pin down, as these largely nocturnal critters are often heard howling at night and often in the direction of the Moon.

Finally, a Blood Moon indicates the coppery colour the Moon turns in mid-eclipse as it enters the Earth’s shadow, when sunlight gets refracted (bent) as it passes through its atmosphere, casting an eerie ruddy hue on the lunar surface.

Timing of the Eclipse:

Starts 02:36 UT

Partial Starts 03:33 UT

Total Starts 04:41 UT

Maximum 05:12 UT

Total Ends 05:43 UT

Partial Ends 06:50 UT

Ends 07:48 UT

 

Conditions as of 00:13UT

Dry, no wind, very cold, 0 C, a wee bit hazy, reducing transparency just a tad. Moon currently transiting the meridian.

Instrument used: 10 x 50 roof prism binocular mounted on a monopod for additional stability and comfortable viewing. Binoculars were made for watching the full Moon, an activity I’ve been enjoying these last few months. I don’t normally observe the Moon when it’s full but binoculars have made it a very worthwhile exercise, especially on nights when some cloud banks cover it. Refraction of Moonrays often produces wonderful displays of colour which are thrilling to observe with ordinary binoculars. My family will join me later during mid-eclipse. My wife will likely reach for her compact 8 x 25 Opticron LEs and the boys will likely be making use of my general purpose, 8 x 42 wide-angle roof prism binocular.

The author’s 10 x 50 binos atop a lightweight monopod.

10 x 50 binoculars are ideal for watching lunar eclipses as they offer decent image scale and a wide field of view for observing stars in the vicinity of the phenomenon.

I hope to estimate the brightness of the mid-eclipse Moon by turning the binocular around and looking through the objective lenses. This reduces the size of the Moon to something much more like a bright star and so is a useful and simple way to compare it to familiar bright winter stars.

I also hope to rate the colour of the umbral shadow, using the five point system devised by the French astronomer, A. Danjon, who proposed the following schema;

L=0 denoting a very dark eclipse, with the Moon almost invisible at mid totality.

L= 1 denoting a dark eclipse, with grey or brownish colourations but with lunar details only discerned with difficulty.

L= 2 denoting a deep red or rusty colouration, with a darker central area and progressively brighter near the lunar edges.

L= 3 denoting a brighter, redder eclipse often with yellowish colours appearing  near the edge.

L= 4 denoting the very brightest eclipse, when the Moon is a coppery red colour, often occurring with prominent bluish shadow rims.

Are we learning Iblis?

Time: 02:28 UT

Conditions remaining good as the eclipse begins. Moon now high in the western sky, a light easterly breeze has started up, bringing some sparse cloud with it. Arcturus rising in the eastern sky; Capella sinking in the west.

Time: 03:37 UT

Partial eclipse now underway; darkening of the limb clearly visible. Thin cloud has moved in and the breeze is still here but lunar visibility still fair to good.

 

Time: 03:48

Moon looks like the Deathstar out of Starwars through the 8 x 25 compact.

Time: 04:02 UT

Some faster moving cloud has rolled in. Amazing display from the clouds in colour and in texture as they move across the face.

04:26 UT

Coppery glows readily seen now. Time to wake the troops.

05:00: UT

Just a few minutes from maximum eclipse. Visibility now very poor, looks like a L=1, but there is also significantly thicker cloud cover. No stars visible for brightness estimate.

Troops a bit underwhelmed.

05:11 UT

Prominent coppery tones from southern hemisphere, brighter near northern limb. Lunar regolith pretty difficult to discern. Visibility quite poor.

Away to bed.

January 22 2019

Postscript: Thoroughly enjoyed the long build up. But as mid-totality approached, the clouds had built up to such an extent that the Moon could only be seen intermittently. The boys found the eclipsed Moon to be quite eerie looking but seeing it well in binoculars or using the naked eye was always interrupted by the encroach of cloud from the west. This cloud formed the basis of a weather system which caused it to rain for most of the day yesterday. My wife thought the event was cool but, like me, she felt that she had witnessed better lunar eclipses in the past.

The apperance of the eclipsed moon looked very much this fine depiction created by veteran sky watcher, David Gray, who is based just a few hundred miles south of our location, only that the details on the lunar regolith were far more subdued owing to the smaller apertures (50mm in our case) employed.

 

De Fideli.

 

 

Resolving Close Double Stars in a 12″ f/5 Dob during Cold Winter Weather.

Doudecim: the author’s 12″ f/5 Dob with a 8 x 50 achromatic finder astride.

 

Description of the Instrument:

Revelation Dobsonian, 305mm aperture with a focal length of 1525mm ( f/5)

Secondary mirror: 70mm minor axis, corresponding to a central obstruction of 22.9%

Primary and secondary mirror origin:  GSO

Primary mirror thickness(measured): 36mm (1.5″)

Mirror cell design: 9 point floatation system.

Both primary and secondary mirrors re-coated with enhanced HiLux coatings each with 97 per cent reflectivity.

Tube: Rollled aluminium, internally lined with a thin layer of cork and overlaid with standard flocking material.

Focuser: 2 speed Crayford style

Length of acclimation from room temperature to ambient: ~2 hours.

Fans used: none.

Finder: standard, straight-through  Revelation 8 x 50 model.

Method of collimation: collimation cap and Chesire eyepiece, verified with Hotech laser collimator.

Time required for precise collimation: 2 minutes.

Introduction:

The reflecting telescope reigns supreme in the 21st century as the telescope of choice for serious students of nearly all disciplines of amateur and professional astronomy. The reason is simple; in the case of Newtonians in particular,  they are, far easier to fabricate and mass produce than any other kind of telescope on the market, and are offered at sensible prices, allowing many people to fruitfully engage with the hobby. Today, an amateur can acquire a truly large telescope thanks to great advances in material science, where a thin layer of aluminium is vacuum deposited onto a carefully figured parabolic glass substrate, avoiding the problem of chromatic and spherical aberrations almost completely.

These days, it is not uncommon for an amateur to own extremely large aperture reflectors – in the 12 to 30 inch aperture class – at prices that don’t cost the earth. The development of the refractor, in contrast, has been severely retarded by the great difficulty and huge expense in producing optics of even moderate aperture. How many amateurs own an 8, 10 or 12 inch refractor? A little researching will soon reveal that very few of us would be willing to shell out the relatively enormous sums of money demanded by the few opticians willing to make them and even professional astronomers would laugh at the suggestion of replacing a large Newtonian or Cassegrain reflector to fund the installation of say a 10 or 12-inch ‘state-of-the art’ apochromat. As a case in point, this author vividly remembers an especially zealous refractor nut who openly called for the alumni of Universities to fund the installation of one such refractor. Not surprisingly, his clarion call fell on deaf ears.

Folk ain’t stupid.

While the Newtonian reflector has deservedly enjoyed a huge following from dedicated planetary and deep sky observers, their use in double star study has been artificially stunted by three decades of nefarious propaganda, instigated by individuals who clearly have little clue about how they behave when properly adjusted and acclimated. Like I said before, it’s easy to get a small refractor to ‘beat’ a large Newtonian if the latter is not adjusted correctly or has not been given enough time to cool down to ambient temperatures, but that hardly constitutes a fair test. Worse still, a subsection of the amateur community dismiss the Newtonian merely because they don’t look as ‘sexy’ as a long, slender refractor. Such individuals have reduced the hobby to something more akin to pornography than anything else. And you don’t have to look long to find it; check out the hysteria over this peashooter, for example. Has anyone not told them that a good 130mm f/5 or 6″ f/8 Newtonian would leave it in the dust, and for about half the price? Like moths to a lamp, they always seem to attract the same motley crew.

As a keen student of the history of astronomy, I have come across many cases where large Newtonian reflectors were used productively to pleasurably observe, or in some cases, even discover new double and multiple star systems. One need only look at the work of such luminaries as Sir William Herschel, Warren De la Rue, Sir William Lassell, the Reverend T.W Webb, William Denning and T.H.E.C. Espin, to name but a few, to see that the Newtonian reflector has been a very productive telescope in the divination of double stars, both for pleasure and for scientific gain. The archives of these historical figures reveal many extraordinary feats of resolution achieved with the Newtonian telescope.  And it is to these individuals that this author has turned to for guidance and inspiration.

Having left the world of small refractors behind, apart from my fabulous achromatic binos and my little ShortTube 80, I set out on an ambitious program of field testing Newtonian reflectors of ever increasing size, having gained intimate experience with the behaviour of the said telescopes in the 3, 5 and 8 inch range, firmly establishing that they are excellent double star instruments. What is more, this author has found through his own experience that a good 8 inch f/6 Newtonian reflector is a much better double star telescope than an optically excellent long focus classical refractor of 5 inch aperture and f/12 relative aperture.

These personal discoveries have led me to more closely investigate the performance of an even larger Newtonian reflector, a standard 12-inch f/5 Dobsonian, which has not enjoyed nearly as much field use than it should have since it was first acquired a few years ago. The limelight was firmly stolen by the smaller instruments, which are easier to deploy in the field, acclimate faster and are less sensitive to the vagaries of the atmosphere, but no more so than with a refractor, or indeed, any other kind of telescope, of the same size. That being said, I have enjoyed many wonderful nights where the traditional bugs that attend Newtonians were either minimal or non-existent, allowing me to obtain truly spectacular views of a suite of double stars traditionally considered ‘tricky’ by my astronomical peers.

In this capacity, this short blog will exemplify the techniques used and the results obtained in observing double stars with such a large, fast telescope.

Method:

What follows is a report of one night- January 8 2019 – between 22:00 and 23:10 UT

Ambient temperature: 0C at 22:00 UT falling to -1C by the end of the vigil at 23:10UT

Conditions: Slightly hazy, no wind, steady atmosphere (Antoniadi II), very cold.

The telescope was brought out from a warm, dry, indoor environment and left to passively cool for 2 hours before the commencement of observations. Though it is fully acknowledged that cooling fans can accelerate the acclimation process and help scrub away the boundary layer on the primary mirror, no such fans were used in keeping with the procedures of the aforementioned historical figures, none of whom had access to (or knowledge of) such fans.

Observer; suitably attired for cold weather observing; several layers of clothing; vest, jumper, overcoat, hand gloves, hat( me ole beanie). No dew shield used.

The following systems were examined in the 12″ f/5 Dob:

Theta Aurigae; a greatly unequal double, primary (A) , magnitude 2.6, secondary (B) magnitude 7.2. Separation 4″.

Iota Cassiopeiae: Triple system: AB- magnitudes 4.6 and 4.9 separated by 2.6″

AC: magnitudes 4.6 & 9, separation 7.1″

Eta Orionis: AB: magntidues 3.6 and 4.9; separation: 1.6″

Eta Geminorum (Propus): AB: magntidues 3.1 and 6, separation ~1.7″

52 Orionis: Classic Dawes pairing; AB equal 6th magnitude components, 1″ separation.

All systems observed either naturally or using a Baader single polarizing filter which cuts glare and increases contrast without imparting a colour shift to the stellar components.

Power employed: 277x throughout (Meade Series 5000 5.5mm UWA ocular).

Results:

The telescope resolved all 5 systems beautifully. The enormous resolving power and light gathering capability of the 30.5cm Newtonian made observing them especially thrilling. While there were many moments during the observations where the stellar images broke up or swelled slightly, there were also many opportunities where the images came together, producing text-book perfect results. As aperture increases, the size of the Airy disk shrinks, allowing the faint, close in companions to be more readily seen.

Iota Cassiopiae was quite simply stunning! All three stars appeared very bright and round as buttons in the 12 inch telescope at 277x. I have not personally experienced a better view of this triple system. Unequal pairs were always more challenging owing to the glare of the primary components, but still readily observed.

Propus(Eta Geminorum); is a particularly difficult system to crack, but on this evening the faint close-in companion presented better than I have ever seen it in my 8″ f/6 Newtonian at any power; the sheer resolving superiority of the 12 inch instrument clearly strutting its stuff.

A polarizing filter screwed into the bottom of the 1.25″ ocular significantly improved the aesthetic of the images by reducing glare and increasing contrast (read darker sky hinterland) very reminscent of a large refractor. Indeed, the filter made it significantly easier to prize the faint companion of Propus and Theta Aurigae in the same instrument.

The closest pairing observed on this evening – 52 Orionis – produced an image that was in a completely different league to any of the smaller Newtonians I have enjoyed testing. The components were much brighter, easier to see with lots of dark space between the components.

All in all; a very good short session under the starry heaven!

Discussion:

The Newtonian reflector has clearly come along way since it was first conceived of by Isaac Newton in the late 1600s. And while speculum metal allowed great gains to be made in both amateur and professional astronomy circles, it may surprise some readers just how far the reflector has been intelligently re-designed ever since those glory days of the past. Did you know, for example, that according to the studies of Dr. Wolfgang Steinicke, an expert on the telescopes at Birr Castle, that the 72 inch Leviathan of Parsonstown had a light gathering power equivalent to a modern, state-of-the-art 25 inch Newtonian reflector [see my book Chronicling the Golden Age of Astronomy,  as well as chapter 7 of William Parsons, 3rd Earl of Rosse: Astronomy and the Castle in Nineteenth-Century Ireland (Charles Mullan ed. 2016)]. Seen in this light, this author considers himself very fortunate indeed to have acquired such a great telescope as the 12 inch f/5 Dob for just a few hundred pounds( it was second hand).

The reader should note that these results are not at all exceptional. Indeed, the author has clocked up many similar nights where the full power of the 12 inch can be pressed into service. Neither is the author out to set any records; the closest pair thus far resolved has only been ~ 0.7″ but the same instrument is fully capable of resolving significantly closer pairs should he wish to pursue them. These results are wholly consistent with the historical archives of many of the early observers mentioned in the introduction, who managed to split extraordinarily close pairs with telescopes of broadly equivalent aperture. For example, T.W. Webb was able to resolve the components of Eta Coronae Borealis using his silver-on-glass 9.5 inch f/8 With-Berthon Newtonian, which had a separation of 0.55″ in the 1870s. Such results make it patently clear that such work can be acheived with larger Newtonians, with excellent results.

Focusing is very challenging in such a fast telescope as the f/5 Reveation Dob. The author very much appreciates the fine focus on the dual-speed Crayford that came with the ‘scope. At f/5 it is a very worthwhile tool in attaining the most precise focus possible.

Filters, such as the Baader single polarizer, are very useful in attaining the right balance between image brightness and contrast. The advantage of using the latter filter is that it does not impart a colour shift to the stellar images, allowing the observer to record the pure colours of the component stars. Using a blue filter will also help resolve the very tightest pairs, as the resolving power of the telescope scales inversely as the wavelength of light used to probe the system. When you have access to such a large telescope, it collects so much light that productive work with even deeply coloured(read low transmittance) filters becomes very worthwhile.

As always, the author would encourage others who have access to such a large Dobsonian to give such systems a try. When careful attention is givien to both collimation and acclimation, the sky’s really the limit!

Thanks for reading and keep looking up!

 

If you liked this blog and wish to support the author, please consider buying a copy of his new book: Chronicling the Golden Age of Astronomy, newly published by Springer-Nature(available in both hardback or electronic formats).

 

De Fideli.

 

 

The Lockyer Sequence

New year’s Day 2019: Plotina starting well on a trail first blazed by Sir Norman Lockyer(1836-1920).

On the evening of January 1 2019, I set up my 130mm f/5 Newtonian astride its Vixen Porta II mount. Conditions were cold, still, and frosty, with temperatures between 0 C and -2C. Seeing was judged to be very good (Antoniadi II).

My purpose this evening was to examine a half dozen double and multiple stars in Orion, as suggested by the distinguished Romanian observer, Mircea Pteancu, who kindly alerted me to a reference made by Norman Lockyer et al in their book, Stargazing: past and present (1878). On page 164 of that book, the authors describe a sequence of double and muliple stars in Orion, which present systems of varying degrees of difficulty for the curious telescopist. After careful collimation and adequate acclimation, the 5.1″ reflector was turned toward the Celestial Hunter, beginning at about 22:00UT and the following systems examined at magnifications ranging from 118x to 566x. The results are shown below:

The Lockyer Sequence.

 

Notes:

The times and magnifications employed are displayed beside the drawings, which depict their orientation in the Newtonian reflector. For all sketches, south is up and west is to the left.

Teasing the close companion to Zeta Orionis apart from its brilliant primary did prove quite tricky, but with a concentrated gaze during the stiller moments, it did yield to the 130mm telescope. The reader will also note the much fainter(10th magnitude) shown at the lower right of the sketch.

The most challenging proved to be 52 Orionis(1″ separation), but with its decent altitude at 22: 43UT, I was able to resolve this classic Dawes pair ( twin 6th magnitude components)  using very high powers. Intriguingly, I first attempted this system by coupling a Meade 3x Barlow lens to a 4.8mm T1 Nagler yielding 405 diameters but without much success. The image was quite dim and very difficult to see the components distinctly. As an experiment, I switched to a Meade Series 5000 5.5mm ultra-wide angle ocular, coupling it to the same 3x Barlow but I also screwed in a 1.6x Astroengineering 1.6x amplifier yielding a power of 566x. To my great surprise, I found the image of the system to be significantly brighter than with the old Nagler and it was much easier to prize the components apart. I can only suggest that the better (read more modern) coatings on the Meade 5.5mm ultra-wide angle allowed greater light throughput, despite the higher powers employed.

566x represents a power of 111x per inch of aperture.

The 130mm f/5 Newtonian continues to surprise and delight me. It’s small, high-quality optics, thermally stable (cork-lined) closed-tube design, and ease of attaining perfect collimation all contribute to its efficacy as a medium-aperture double star instrument.

I would encourage others who have similar equipment to give these beautiful systems a visit. What better way to entertain and challenge a dedicated observer on a cold winter’s evening!

 

 

De Fideli.

For the Record.

Plotina: raising the bar for grab ‘n’ go astronomy.

 

2018 was not an unusual year here in Scotland, as astronomical observing and associated note-making are concerned.

Total number of nights where observations were made in 2018: 137

Percentage of nights available for observation in 2018: 37.5 per cent.

This is in accord with the claims of several British historical observers; T.W Webb, William F. Denning & Charles Grover.

For more details on this interesting topic, see my new book: Chronicling the Golden Age of Astronomy.

De Fideli

A Winter Adventure with a 130mm f/5 Newtonian.

Plotina; the author’s 130mm f/5 Newtonian doing its stuff under a Christmas sky.

Sunday, December 23 2018

With the Christmas holidays now upon us, we were lucky enough to enjoy a beautiful  winter day, with clear blue skies illumined by a feeble Sun. This time of year, darkness falls very early, well before supper time, and as luck would have it, the sky remained clear after dark. I decided to field my trusty 130mm f/5 reflector, mounting the telescope on an old Vixen Porta II mount at about 4.00pm local time, and let it cool down to ambient temperatures, which had already reached 0 C by sunset. Accompanying the telescope was a 8 x 42 roof prism binocular, used for finding fainter objects more quickly than with the telescope and its finder alone.

The cold weather was never a concern though; afterall, the telescope has strutted its stuff many times in sub-zero temperatures, as I’ve described in many previous blogs. At 4.45pm I began my observations with a look at the Red Planet, Mars, which by now had greatly receded from the Earth, but at least had now reached a very decent altitude in the south. Inserting a Parks Gold 7.5mm eyepiece coupled to a Meade 3x achromatic Barlow lens yielding a power of 260 diameters, I was greeted by a tiny little salmon-pink orb, quite obviously gibbous in cast, with a few dark markings visible across its surface. The view was good and steady and very satisfying given the great distance to which it had receded to since its glory days during the summer, when the planet swelled to an enormous size as seen through the same telescope.

But what I was really after this evening was a suite of double stars, my staple observational targets for many years now. Having abandoned small refractors and Maksutovs for the greater efficacy of the 5.1 inch Newtonian reflector, I turned the instrument on Epsilon 1 & 2 Lyrae, a summer favourite, but still suitably placed for observation in the early evenings of December. Keeping the same eyepiece and Barlow in the focuser, I obtained a wonderful, text-book perfect split of all four components. And though I had seen such an apparition more times than I care to remember, it still brought a broad smile to my face to see these old friends in a Christmas sky.

From there, I moved over to Delta Cygni, a much better test of atmospheric turbulence than the four stars of Epsilon Lyrae. Carfeully centring and focusing the bright white luminary, I obtained an excellent and stable image of the faint, close-in companion at 260x. It was at that point I knew that conditions were good enough to attempt the trickier targets that were lining up in the sky.

Moving the telescope further west, I could see bright Altair, so I tried my hands at the difficult and faint Pi Aquliae nearby, which I first reconnoitred with the 8 x42, before centring it in the 6 x 30 finder ‘scope of the main telescope. Keeping the power at 260x, I achieved a reasonable split of these fairly closely matched components but I could see that it was noticeably inferior to how it looked in the late summer and early autumn, when it was higher up in southern skies. Still, I was well chuffed to have bagged this system so late in the season.

Moving several degrees east into the diminutive but lovely constellation of Delphinus, I immediately aimed for the jewel of the celestial Dolphin; Gamma Delphini. The 5.1″ reflector made light work of this easy but fetching double star which was best seen at 118x using my Meade 5.5mm Ultra-wide angle eyepiece. From there, I sped over to Cygnus again and quickly located the multiple star, o^1 Cygni using the 8 x 42. Training the telescope on the system brought another huge smile to my face, as the beautiful and wide colour constrast triple system came to a perfect focus, their tiny Airy disks and faint first diffraction rings calmly presenting themselves in the frigid air.

After that, I panned the telescope eastward until I centred Almach (Gamma Andromedae) in the 118x eyepiece and was greeted with a beautiful split of this comely, colour-contrast double star. Even after all these years of observing it, it never ceases to inspire me! “That was easy,” I said to myself, ” but let’s have a go at a much more tricky system.” With that thought I trained my binocular at a patch of sky in eastern Cygnus, specificially looking for a faint pair of stars, the brighter of which was Mu Cygni. Quickly aligning the telescope on the same patch of sky, I inserted the 260x eyepiece-Barlow combination described earlier and carefully focused. Voila! There it was; a wonderful text-book perfect split of this very close binary system, with the wider, fainter star visible in the same field comprising the triple.

Finally, I visited the endlessly lovely Albireo, now fairly low in the western sky. Needless to say, it was a sight for sore eyes. It’s true; some of the most beautiful objects in the night sky are the easiest to access!

So far, so good. I took a break for a few hours, enjoying a good, traditional Christmas roast with my family, keeping the telescope in an unheated outhouse all the while, so as to allow me to quickly engage with the night sky. Beginning again around 10:15pm, with the bright Moon having risen in the sky and the temperatures having dropped to -2C, I  started in Orion, which at the time of observation, had still not culiminated in the south. Hoping for a continuation of the steady skies experienced earlier in the evening, I trained the 130mm Newtonian on mighty Rigel. Slightly anxious, I carefully focused the bright white luminary in the 118x eyepiece and was relieved to see that the primary Airy disc was small, round and virtually free of turbulence. And there beside it was the tiny spark from its feeble, close-in companion. It was a beguiling sight!

From there I moved a wee bit to the northeast and centred Eta Orionis.This is a more difficult pair to resolve and so requires higher powers to tease apart. But at 260x it was easy; the two stars, plain white to my eye, appeared roughly east to west in orientation.

By now, mighty Auriga, the Charioteer, had risen to a great altitude, high in the east, and so I turned the telescope on its most prestigious double star; Theta Aurigae. The telescope made light work of this tricky system, the faint, steely grey companion being stably held in the frosty air.

A night of winter double star observing could never be complete without a quick look at Castor A & B in Gemini. Just east of the bright, near-full Moon, I had to battle with the glare a bit before centring the system in my 6 x 30 finder ‘scope. But at 260x, the twin white stars, pure as the driven snow, was a msemerizing sight in the telescope; the Airy disks small and round as buttons, each surrounded by a single, faint diffraction ring.

Finally, I thought I would try my hand at 36 Andromedae, which was first found with a bit of ferreting around using the 8 x 42 binocular. And sure enough, I was able to split this 1 arc second, near equally bright pair in the telescope without much effort at 260x. However, it was better seen using the higher power of a 4.8mm T1 Nagler eyepiece coupled to the same 3x Barlow yielding 408x. I was mightily impressed with just how good and stable the image remained as it shot across the field of view at this ultra-high power.

Vigil ended shortly before 11pm local time.

What a great night!

Simple pleasures with a simple telescope!

The stuff dreams are made of.

 

De Fideli.

The Year in Review

Plotina: the author’s 130mm f/5 travelling Newtonian sampling the beautiful autumnal skies of Dumfries & Galloway, southwest Scotland.

Anno Domini MMXVIII

We’ve reached the end of yet another year; and boy do they come round fast and furious! It seems like yesterday when the freezing Beast from the East was upon us, and that gave way to a unusually warm summer. Our family ventured across the waters to visit my brethern remaining in the south of Ireland and to catch up with old friends and acquaintances. But it was also a year where I made considerable progress establishing how good the British Isles are for doing all kinds of astronomy, having completed a survey of a dozen or so different sites across the British Isles. Despite the prognostications of casual observers, Britain and Ireland possess many prime locations to conduct visual astronomy, and in particular, high-resolution double star astronomy using small and medium-sized Newtonian reflectors.

In August, I conducted a month-long observational program to establish to what extent the Jet Stream affected my ability to resolve a variety of double stars ranging from between 1 and 2″ angular separation, finding no real evidence in support of its alleged effects and that it need not deter a determined observer to enjoy visual astronomy. It was, to my knowledge, the first such survey to be conducted on the subject.

My scepticism concerning the virtues of small, expensive refractors grew ever stronger throughout 2018, when I finally rid myself of the last remaining apochromatic refractor in my stable. As I have exhaustively shown, a much simpler and less expensive 130mm f/5 Newtonian proved superior to a 90mm ED glass on all sky targets. The former instrument has become my grab ‘n’ go telescope of choice, based solely on optical performance.

I will not be updating my book on refractors, as my conscience will not countenance the continued cultivation of untruths about their supposed virtues in the field.

I’m a Newtonian convert!

In another project, I tested a variety of optical devices that enable observers to use Newtonian reflectors during daylight hours, finding that the 130mm f/5 Newtonian coupled to a Vixen erect image adapter to be a fine, cost-effective alternative to large, expensive ED spotting ‘scopes.

Schmokin; the Vixen terrestrial image adapter.

My continuing blog entitled: the War on Truth: the Triumph of Newtoniasm, I have collated the opinions of a large volume of observers and authorities in the field from around the world, both historical and contemporary, which clearly show that Newtonian reflectors in the 8- to 12-inch aperture class will outperform smaller refractors at a fraction of the price, in sharp contradistinction to two decades of nefarious promotion by so-called ‘experienced’ amateurs. One of the key reasons for this blurring of the truth pertains to my suspicion that many refractor enthusiasts either don’t know, or are unwilling, to accurately collimate these instruments and/or are too lazy to allow adequate thermal acclimation of the same.

That being said, I have been very encouraged by the response of the amateur community to this legitimate protest. It seems many more former refractor onlyists are willing to consider the Newtonian once more and that’s a good thing!

2018 has also been a year where I have re-discovered the considerable virtues of binoculars. As a series of recent blogs showed, I have found a range of optically excellent roof prism binoculars that suit the budgets of many more amateurs, enabling the hobby to grow and not stagnate. Although I have certainly not spent a small fortune buying every other model, as others have done, I quickly gravitated towards two instruments, both made by Barr & Stroud, a 10 x 50 unit for dedicated binocular astronomy using a monopod, and a most excellent 8 x 42 Savannah wide-angle instrument for casual stargazing and nature observation. The latter has become a constant companion on my long country walks. I sincerely wish that others will test these binoculars themselves and spread the love.

An amazing, general purpose binocular; the Barr & Stroud  Savannah 8 x 42 wide angle.

I intend to drastically cull my current crop of astronomy equipment in 2019 as it has weighed heavy on my mind of late. I have retired mighty Octavius, my 8 inch f/6 Newtonian reflector, as it has achieved everything I intended for it and much more besides. My intention is to eventually gift it to some keen amateur who will use it productively. My 5 inch f/12 refractor is similarly retired. The little Orion SpaceProbe 3 alt-azimuth reflector and my old 7 x 50s were bequeathed to Gavin, a very enthusiastic young man of 8, who showed unusual interest in astronomy, and uses them regularly to stargaze from his home just outside our village.

I plan to use just three instruments in the coming year:

A 12″ f/5 Newtonian(Duodecim)

A 130mm F/5 Newtonian(Plotina)

Binoculars.

These three instruments will enable me to enagage with the full gamut of amateur astronomy. They are all I could possibly want!

Duodecim: a fine 12″ f/5 Newtonian reflector.

I would like to produce more blogs on binocular astronomy in the coming year, Lord willing, as well as produce new reports with both the 130mm f/5 and 12″ f/5 instruments.

2018 marked the end of a long slog to get my new book into shape; Chronicling the Golden Age of Astronomy. It’s been five years in the making, but it was an enjoyable and worthwhile project, bringing together the selected works of many amateur and professional astronomers across four centuries of time, who used their telescopes, both great and small, to create the wonderful hobby we enjoy today. What I learned from their diligent adventures under the stars is incalulable and I have tried hard to capture the essence of their life and researches in this large, historical work. It is my fondest hope that it will be well received by my peers. Please check out the reviews as they appear.

A work dedicated to the heroes & heroines of our hobby.

Finally, I am in the process of writing a new book dedicated to the ShortTube 80 achromatic telescope which ought to be available at the end of 2019. I have amassed a large body of notes from several years of using this quirky little telescope in the field, which I hope will be of interest to the many amateurs, young and old alike, who use or have used the instrument in the past.

So, there it is!

God bless you all!

Neil.

 

De Fideli.

Another Binocular Review: The Barr & Stroud Savannah 8 x 42 Wide-Angle.

One of the best on a budget: the Barr & Stroud wide angle Savannah 8 x 42 roof prism binocular.

 

What’s in a name?

I found myself asking this question after taking a chance on a number of decently priced roof prism binoculars made by Barr & Stroud, which completely surprised me. Barr & Stroud have long since ceased from trading as an independent company but a name remains valuable, that’s for sure. Perhaps it’s the know-how they leave with the parent company who buys them out? Maybe it’s the work ethic associated with the name? Whatever it is, they sure know how to put together a quality optic!

My evidence for this rests in three binoculars I’ve tested from the line offered by Barr & Stroud; the Sahara 8 x 42, the Sierrra 8x 42 , and a larger instrument, the 10 x 50 Sierra used exclusively for astronomy. Indeed, user reviews of these instruments seem to be almost universally favourable, with many claiming that they shoot well above their weight, especially for their modest price tag. The experience with these units confirmed a suspicion I have entertained for quite some time; that in this day and age there is no need to opt for premium models costing upwards of £1000, as quality has improved so much as to render them largerly unnecessary for the vast majority of enthusiasts. Excellent optics need not cost the Earth.

I chose the 8 x 42 roof prism binocular because of its compactness and rugged design that is less prone to mis-alignment than the equivalent porro-prism models being offered. It is the ideal cross-over binocular, allowing one to enjoy fabulous views of the landscape by day and very satisfying casual observation of the heavens by night. The 8 x 42 reigns supreme among birders and hunters for some years now, as its decent light gathering power and ultra-portability allows viewing objects under low light conditions, as is often experienced at dawn and dusk, as well as the failing light of mid-winter.

I have been blissfully happy with the Barr & Stroud 8 x 42 Sierra, as it seemed to offer all the things I wanted in a versatile, multi-purpose binocular, but I was still highly intrigued by yet another model marketed under the same brand name which seemed to be garnering even better reviews from consumers; enter the  8 x 42 Savannah.

Being intrigued is one thing though; parting with my hard-earned cash was quite another. But how else was I going to find out? It was at this juncture that a compromise was reached; if I could get a lightly used Savannah for a good price, I could satisfy my curiosity and allow me to complete my survey of the full gamut of what Barr & Stroud were offering to the budget conscious consumer. An opportunity soon arose when my interest was piqued by an advert posted on the dreaded ‘fleabay’. The seller posted some high quality images of a 8 x 42 Savannah, indicating that it was used only a few times and that she had misplaced the little cap that covered the thread allowing the instrument to be mounted on a monopod or tripod. She was offering £80 for the unit plus £6 shipping. That represented a 50 per cent saving on the new price, so I bit the bullet and pulled the trigger on a sale.

As I explained in a previous blog, I was cautious about going for a binocular that offered an overly generous field of view, but when I read the reviews I noticed that no one was complaining about off-axis distortions in the Savannah, which sported a relatively huge perspective; 143 metres at 1000m, or an angular field of view 8.2 degrees wide! Afterall, this was a full degree wider than that offered by the 8 x 42 Sierra. Man, that’s a wide field, wider in fact than the vast majority of views offered even by premium manufacturers! For example, one of the widest models, the Zeiss Victory SF 8 x 42 offers a field of 148m at 1000m, so not far off the Savannah!

A few days after I made the purchase, the package arrived safely at my home. The owner had carefully packed it for transport up from England to bonnie Scotland. Inspecting the unit, I was relieved to see that all was well; I got the original hard case, the Savannah binocular with the ocular cups and strap attached, a lens cleaning cloth, the one-page generic instruction sheet, and of course, that valuable 10 year warranty. Cool.

The Barr & Stroud Savannah 8 x 42 roof prism binocular complete with stylish hard case, 10 year warranty card and single page instruction sheet.

I was quickly able to replace the missing B&S cap with the one borrowed from my 10 x 50 Sierra, which was now permanently affixed to the monopod adapter previously described in this link. So now, I had the complete binocular, cap an’ all.

Both the ocular lenses and the objectives looked pristine, with no defects that I could see.

Looking down at the ocular lenses. Note the specifications.

The pristine 42mm aperture objectives on the Savannah. Note the replaced B&S cap. Rubber objective lens caps come as standard with all the Barr & Stroud binoculars and fit  snugly and firmly in place so they won’t get dropped or lost easily.

The Savannah 8 x 42 has a number of different mechanical features in comparison to the Sierra model, including a slighlty larger focus wheel and a re-designed diopter adjustment mechanism situated immediately ahead of it. The binocular is a little heavier than the Sierra though, which I counted as a disadvantage, but that said, it is very solidly built with excellent fit and feel, courtesy of its tough, rubberised overcoat. I was surprised to learn though that even with its increased weight, it was about the same weight as many of the premium models on the market offering the same or similar specifications.Like the other Barr & Stroud models, the Savannah is weather proof, purged internally with dry nitrogen gas and O-ring sealed.

The twist-up ocular caps are slightly different on this model also, being slightly flatter and, dare I say, look a bit more elegant than on the Sierra and Sahara models. The Savannah offers the same generous eye relief to the user; 18mm, so are ideal for both eye glass wearers and those who prefer to observe without glasses.

The eyecups twist up securely in two clicks for use without eye glasses.

 

Like the Sierra, the Savannah 8 x 42 has an excellent close focus distance of just two metres. The diopter setting is not quite as rigid as the Sierra model though, requiring frequent checking to ensure that it remains in the desired position for optimal binocular performance. The Savannah is also fully multi-coated and the prisms are appropriately phase coated for the highest possible light transmission.

The Savannah comes with a much higher quality and more comfortable carrying strap, featuring the Barr & Stroud logo, which is a definite improvement over the basic strap accompanying the other models tested. This will be very much appreciated by those who use the instrument during prolonged field use.

A better padded carrying strap with the B&S logo comes standard with the Savannah range making their transport in the field more comfortable.

Optical Testing

Although the precise diopter adjustment can be closely approximated in daylight targets, I have learned to tweak it by focusing on stars at night. Specifically, what I’ve found is that the diopter position acheived during routine observations in the daytime are, more often than not, very slightly out when observing point sources like bright stars at night. This can be seen by a slight spiking of the starlight at best focus, which can thereafter be eliminated by making minute adjustments to the diopter dial. I would recommend this technique to others to get the best possible views out of their binoculars.

Focusing is very precise and intuitive and produces exquitely sharp images that display the objects in their vivid colours accurately and in very high contrast. In my research of some of the premium models, I discovered that in their quest to attain the highest levels of light transmission (95 per cent in this case), many experienced observers reported that the colour tone turned out to be a bit on the dull, or ‘cold’ side. Remarkably, the manufacturers opted to slightly reduce light transmission by a few per cent in order to generate more natural colour tones in their newer models. The Savannah suffers little from these problems however as the colour tones appear very natural and fully in keeping with a high quality field binocular. For more on this interesting development see this link.

Chromatic correction is excellent; you’ll only see it if you look very hard for it around high contrast objects when set against a bright overcast sky. No need for ED elements in a glass of this specification; an expedient luxury that adds practically nothing to the viewing experience. Of course, there will always be those who insist on having this feature; good luck with that!

The main reason I took a chance on the Savannah 8 x 42 is its prodigious field of view. Expecting to be a little underwhelmed, I was very pleasantly surprised to discover that the images remain very sharp across the vast majority of the field with only slight softening observed at the extreme edge. The same was true when I tested them out on bright star fields. The stellar images remained acceptably sharp over a field considerably larger than the 8x 42 Sierra, with negligible distortion at the extreme edge of the field. What absolutely blew me away though was an experience I had during the first week in December 2018, when I turned the Savannah 8 x 42 on the constellation of Orion which had now culminated in the south in the wee small hours. I was able to image the entire Sword Handle and the three bright belt stars of the Celestial Hunter with some room to spare! Both contrast and sharpness were very impressive and arguably one of the most immersive views I have ever enjoyed in any binocular! Internal reflections and flaring are also very well controlled.

The price one has to pay for this 25 per cent increase in field area over the Sierra model is increased mass; 819g as opposed to just 650g in the latter. Was the tradeoff worth it? I would have to say yes! The enormous, well-corrected field is quite simply awesome and worth experiencing despite the greater weight. I guess to create this brilliant wide field, one has to re-think the optics of this design and that necessitated adding different (or just more?) ocular lenses to the instrument.

Spiffing good.

So I wound up with two 8 x 42s. Now, as I’m no collector and don’t believe in hoarding stuff, I decided to gift the Sierra to a friend. I now have my ideal multi-purpose binocular and would unhesitatingly recommend it to anyone looking for a great, no-nonsense instrument at a very decent price (even new!).

Postscriptum: Check out what this youtuber had to say about the Barr & Stroud 8 x 42 Savannah binocular.

Full specifications of the instrument here.

 

Neil English is the author of Chronicling the Golden Age of Astronomy.

 

De Fideli.

 

 

Product Review: The Barr & Stroud Sierra 10×50 Roof Prism Binocular.

The Barr & Stroud Sierra 10 x 50 binocular with peripheral eyeshields.

 

There has never been a better time for the binocular enthusiast. Nowadays, a huge range of models are available that offer high quality optics for nature studies, birding and astronomy. Doubtless, this revolution is wrought by advances in technology; better glass, better coatings,  as well as steady progress in materials science. Greater competition among the various optics houses also helps drive prices down, so that many more people can take advantage of this new technological wave; and that is good news for a multitude of hobbyists.

I recently described my very favourable impressions of a new instrument; the Barr & Stroud Sierra 8 x 42 roof prism binocular, which offers excellent optics, good weather proofing, great compactness and very light weight compared with my old, well-worn 7 x 50 porro-prism binocular, which had served me well for three decades. The 8 x 42 is an ideal instrument for daytime applications, where its decent light gathering power and efficient transmission of light to the eye, yields images that have great colour fidelity and excellent contrast. As I also explained, the 8 x 42 can be used productively for night-time applications, where it offers good performance within the remit of its aperture.

Still, as good as the 8 x 42 is, I felt I was missing out a little were I to use the instrument for specialised deep sky viewing, compared with slightly larger instruments that have long been the staple of the binocular astronomy enthusiast; I wanted to be able to do binocular astronomy using only a binocular; under its own terms.

Enter the venerable  10 x 50. And that prompted me to seek out a high quality instrument that I could almost exclusively dedicate to night sky use. A good 10 x 50 would gain about about a half a visual magnitude over the 8 x 42 and its slightly higher magnification would be advantageous for pulling out faint deep sky objects that are not so well seen with the smaller binocular.  I had heard some great things about the Nikon Aculon 10 x 50 porro prism binocular and I seriously thought about acquiring it, since it seemed to offer a lot of bang for the buck, but when I considered its weight- 898g, it seemed rather on the heavy side. You see for me, weight is a brute fact: the heavier the binocular, the less I would likely use it.

Deeply impressed by the way the compact 8 x 42 handled various situations, I looked again for a roof prism model offering 10 x 50 specifications and it wasn’t long before my interest was piqued by the Barr & Stroud Sierra 10 x 50 roof prism binocular, which I felt was very reasonably priced. So I took the plunge and ordered one up.

Just like the 8 x 42, the 10 x 50 Sierra arrived very well packaged in an attractive box. The same soft, black carry case housed the binocular, as well as receiving the neat 10-year warranty card and single page instruction sheet.

The 10 x50 Sierra binocular in its soft carry case.

 

The binocular is very well built, with a strong, rigid bridge that is not easily moved once the proper interpupillary distance was set. Ditto for the diopter setting, which is quite stiff and thus not likely to budge in field use. Like the 8 x 42, the unit is o-ring sealed and purged with dry nitrogen gas making it fog and weatherproof (water resistant up to 1.5m for three minutes), Its weight is considerably lower than the Aculon; just 780g. The focuser is smooth and firm to the touch and offers an excellent close focus distance of just 2.5 metres (tested). It also has rubberised caps to protect both the objective lenses and the eyepieces. What’s more, they can be permanently affixed to the binocular so they won’t get lost in a hurry.

The 10 x 50 Sierra is fully multi-coated and the prisms are phase coated for optimum field performance.

 

Like the  8 x 42 Sierra, the 10 x 50 unit features fully multi-coated optics and the BaK-4 roof prisms are phase coated to maximise image brightness, contrast and colour fidelity.

Very nicely designed oculars ensure comfortable viewing, either with or without eye glasses. Note; the oculars are shown fitted with eyeshield peripheral shades (purchased separately).

The eyecups can be twisted upwards for use without eyeglasses, or can be kept fully down if oe decides to use them with eyeglasses.

Eye relief is very generous 17.8mm and the field of view offered is just under 6 angular degrees.

Full details of the 10 x 50 Sierra can be viewed here.

The very same afternoon the 10 x 50 Sierra arrived, I took off on my long country walk to see how they performed during daylight hours. The first thing I noticed was their additional weight; fully 130g heavier than the 8 x 42 Sierra. After a few miles of walking with the instrument hanging around my neck, I experienced significantly greater back strain than I was accustomed to carrying the lighter 8 x 42. This was fully expected however and affirmed my conviction that 8 x 42 would better serve me during daylight hours.

I fully expected a little more chromatic aberration, given the specifications of the 10 x 50 and this was confirmed by focusing on a distant hilltop against a bright overcast sky. Still, it was very minimal and perfectly acceptable. Certainly, it would never be enough for me to consider a model with ED glass; that would be overkill to say the least! The images served up by the 10 x 50 were beautiful, crisp and bright, with great colour fidelity and excellent contrast, although it was immediately acknowledged that I would be sacrificing some field of view over the 8 x 42.

While using the 8 x 42 for prolonged periods during my daily walks, I noticed that on bright days, light entering my peripheral vision was causing some annoying glare to seep in. This had nothing to do with the type or make of binocular but merely reflected an operational issue while using any binocular. Thankfully, I found a great solution; enter Eyeshields produced by a US-based company called Field Optics Research.

A good product for any binocular user. Eyeshields by Field Optics Research.

 

Costing £25 delivered, I received two pairs (one for the 8 x 42 and the other for the 10 x 50) of eyeshields which fit snugly onto the oculars and can be deployed at a moment’s notice. They remain permanently affixed to the eyepieces and fold down when not in use. Another neat feature of the EyeShields is that you can still use the rubberised dust caps with them on. They do a simple job, shileding your peripheral vision from stray light, but also stop wind-driven dust from accumulating on the oculars. They work really well, effectively eliminating the said glare I was encountering during my observations. Though a bit costly for what they really are- rubber eyeshields in a tin box lol –  I can certainly vouch for their effectiveness and would highly recommend them to any binocular enthusiast.

One thing caught my attention though: I noticed that the company state that the product is “patent pending”. I don’t know if something like this can really be patented though. I mean, I have similar eyeshields which came with some of my older orthoscopic and Plossl eyepieces, so it’s hardly something truly novel.

The eyeshields very effectively block peripheral light entering the eye while using binoculars in bright ambient light settings.

Ad Astra

Though I acquired the binocular at the start of November 2018, I was not able to conduct star tests until the evening of November 7, owing to a prolonged bout of cloudy, damp and misty weather, typical for this time of year, which all but extinguished the light from the stars. Seeing some breaks in the clouds after dark stoked deep feelings of joy, and I immediately grabbed the 10 x 50 to begin my observations. My first impressions were very favourable. This cost-effective instrument served up beautiful views of the Pleaides, my first target in northern Taurus. I immediately appreciated the wonderful contrast of the instrument and could instantly make out many more fainter members than I could see with the 8 x 42. The increased image scale was quite significant too, framing the asterism very well in the field of view.

Two tests of the size of the field were conducted; first with the Hyades, which was quite simply stunning in the 10 x 50 and I was delighted to see that the main ‘V’ shaped configuration was nicely framed in the binocular field with a little room to spare. The field came alive with many sparkling jewels, brighter and more numerous than in the 8 x 42. Star colours seemed even more vivid too.  Since the main part of the Hyades is in excess of 5 angular degrees wide, this comported well with the field quoted in the specifications table.

In the second test, I was able to get brilliant white Rigel just inside the same field as the Orion Nebula (M42), a distance I estimated to be about 5.7 angular degrees, so quite close to what the manufacturer claimed. It’s nice when the stated specifications agree with experience!

At tightest focus, brilliant yellow Capella in Auriga showed no fringing of any sort that my average eyes could detect, and moving the brilliant autumn luminary to the edge of the field showed that it remained agreeably sharp and tight; perhaps even a tad better than the wider field offered up by the smaller 8 x 42. I reasoned that this was not to be unexpected, as it is easier to get a better corrected field as the field shrinks in size.

Sweeping the binocular through the heart of Auriga showed its clear superiority over the 8 x 42. The 3 Messier open clusters were easier to pull out from the background sky and I was also able to more easily see a number of other fainter nebulae that were mere suggestions in the smaller Sierra binocular.

As a resolution test, I steadied the binocular on the side wall of my house and aimed it at golden Albireo, now rather low in the northwestern sky. I believe I was just able to pick off its companion, something I have not been able to achieve using the 8 x 42 after several attempts.

The weight difference between the Sierra binoculars is immediately obvious under the painted canopy of the night sky. It is harder to hold the 10 x 50 steady, but I find that this is less important for large deep sky objects than it is for studying smaller targets like individual stars, where the wondrous creation of the human eye-brain seems to act as a natural image stabiliser. I found it beneficial to move my hands further forward in order to get a better grip of the objective end of the instrument while in field use. This strategy definitely helps me to get the most stable images from the 10 x 50 during prolonged (greater than 20 seconds or so) observations.

In another test, I compared the binocular views of M 35 in Gemini, which had cliimbed out of the eastern murk, reaching a decent height just after local midnight. While both binoculars easily showed the large, roughly wedge-shaped open cluster, its sub-optimal altitude enabled only a few stellar members to be made out in the 8 x 42 but many more were discernible with the larger 10 x 50.

Some other daylight tests:

Many inexpensive binoculars often come with misaligned prisms which cut off some of the light reaching the eye. This is especially true when the product comes via courier. I’ve had a large 15 x 70 binocular in the past that came badly misaligned, which made me far more cautious about buying a binocular online. Thankfully, this was not the case with the Barr & Stroud binoculars, which were all properly and securely collimated in the factory prior to dispatch.

A simple way to test this is to examine the shape of the exit pupil of the binocular when pointed at a bright light source. A square or non circular shaped light shaft is an easy way to show if the prisms are undersized (thus losing some light) or misaligned. As the photo below shows, the exit pupils of the 10 x 50 are round, as are the 8 x 42s,  indicating that all is well.

No sign of a squared off exit pupil on the Barr & Stroud binocular.

 

Like the 8 x 42 previously tested, the 10 x 50 showed little sign of pincushion distortion while examining the profile of a horizontal roof located about 100 yards distant.

Attaining binocular stability without sacrificing mobility

As I stated previously, binocular astronomy, for me, generally means hand-held viewing, without the need for tripods or other more elaborate kinds of mounts that just get in the way. That’s one of the reasons why I eventually grew disillusioned with large and heavy binoculars. But any 10 x 50 unit, whether roof- or porro prism-based, will eventually show its limitations in regard to attaining rock steady views of star fields, or for teasing apart tighter binocular double stars, or even for seeing the most detail on the Moon. One way round the problem is to stabilise the binocular on a fence or a wall, but this convenience is not always practicle, especially if you’re on the move. The best compromise is to use a lightweight monopod and it is to this device that I turned to in field testing.

One thing the reader must be made aware of is that roof prism binoculars will not, in general, be compatible with standard porro prism binocular tripod adapters. Many of these adapters might fit the roof prism binocular but the stalk will more often than not be too wide to attain the optimum interpupillary distance so important for the most comfortable, immersive views. To that end, I ordered up a smaller adapter especially designed for medium sized (up to 50mm aperture) roof prism binoculars. I elected to go for a well machined, high-quality unit marketed by Opticron (shown below).

The Opticron tripod adapter designed for medium sized roof prism binoculars.

Having acquired a monopod some time ago for use in landscape photography, I was eager to see how the binocular would fare using this configuration, so I began a set of field tests using this device to see if it would tick all the boxes.

The Opticron adapter mates to the 10 x 50 Sierra very well, enabling the correct interpupillary distance to be maintained.

A good fitting: the Opictron tripod adapter mates to the binocular perfectly and will allow the user to re-adjust the interpupillary distance for optimum field performance.

 

The binocular with its adapter readily screws into the monopod. The whole configuration is still very lightweight, ultraportable and is now ready for testing under the night sky.

The 10 x 50 Sierra securely mounted on the lightweight monopod.

To what degree will the monopod stabilise the images in the 10 x 50? Off the bat, it will yield images that are more stable than an image-stabilised (IS) binocular, without the attending arm strain, high cost and need for battery power, but will fall short of that generated by a tripod.

Shortly before local midnight on the evening of November 15 2018, I stuck my head out my back door to discover that the sky had cleared somewhat after a rainy spell. The air was grand and mild, and the Moon had set shortly after 11pm, yielding a fine, dark sky. Pleasantly surprised, I ran in and fetched the 10 x 50 atop the monopod. The Pleiades was very high up in the south; ideally placed for binocular viewing. Settling into my recliner, I was able to negotiate a very comfortable position with the monopod securely held against the ground. Centring the asterism in the field of view, I was dumb struck by how good the view was; a blizzard of blue white stars piercing through the canopy of night in a blaze of glory! The effect of stabilising the view makes an enormous difference to what you see. Some highly experienced binocular users claim that you can go up to a magnitude fainter if the image is stabilised. I don’t know whether that’s accurate or not, but what I can say is that it was a supremely joyful experience. I just lay there for twenty minutes in the dark feasting my eyes on the celestial apparition before me. During the spell, cloud patches of varying thickness marched across the sky, diminishing the brilliance of the Pleiads by varying degrees, but as they passed through the full splendour of the cluster reasserted itself.

I will add a strong ball & socket adapter to the monopod so that I can make angular adjustments to the binocular. That way, I will increase the viewing comfort that little bit more.

That was my first experience with the monopod; a first step. In time, I’ll take another.

November 17 2018:

After rummaging around in me ole box of tricks, I selected a good ball & socket adapter for the 10 x 50 binocular. Although I had a few of these handy, I elected to use one that could carry the 780g instrument with ease. My best one, shown below, can carry cameras and other equipment up to 2 kilos in weight.

An all-metal ball & socket adapter mated to the monopod with a 2 kilo carrying capacity.

 

It worked really well with the binocular in daylight tests. Indeed, it will give me yet another degree of freedom whilst conducting my observations of the night sky.

Another view of the ball & socket adapter mounted on the monopod.

 

So, there it is; I think I’m ready for another session under the stars. What attracts me to this arrangement is its sheer simplicity; increased stability, easy to carry, easy to manoeuvre, easy to store away!

Simplicity itself.

Round about 6pm local time, I ventured out to see if the clear spells we enjoyed during the afternoon had persisted. I was in luck. The 10 day old gibbous Moon was low in the southeast, still a couple of hours before meridian transit. Eagerly, I turned the 10 x 50 astride the monocular mount at it, focused, and then carefully assessed the image.

I was very pleased! Our 70 per cent illuminated satellite showed some wonderful detail, easily superior to the smaller 8 x 42. The prominent ray crater, Copernicus, stood out a mile, as did Clavius and Tycho in the southern highlands. Eratosthenes, Plato and Archimedes proved easy too. The Apennine Mountains were clearly seen running from northeast to southwest and the various maria; Tranquillitatis, Fecunditatis, Serentatis, Nubium and Imbrium were all beautifully presented. Some faint stars in the vicinity of the Moon were easily seen in the 10 x 50. Thin, whispy clouds often ran across the lunar countenance, acting like a natural filter and increasing contrast. The upper edge of the Moon had a very thin bluish hue, whereas its southern counterpart was similarly tinged yellow. I attributed this in the main part to atmospheric refraction owing to its fairly low altitude (20 degrees) at the time the observation was made. Even at its brightest, glare was really well supressed, just like the 8 x 42 Sierra.

The Moon really comes alive in the image-stabilised 10 x 50!

The observations were conducted just standing up with the monopod, and I was able to tweak its pointing accuracy by making small adjustments to the ball & socket bearing. Turning over to the east, I aimed the binocular at Alpha Persei and made some more adjustments to the ball & socket so as to obtain the most comfortable standing observation of the binocular field. Even in bright moonlight, the rich starfields around it were wonderful and sharp almost all the way out to the edge, with excellent contrast.

Final testing: November 18-20 2018

Guid graith.

With unsettled weather being the rule rather than the exception over the last few days, my final tests were mainly conducted on a bright gibbous Moon, now rising much higher in the sky than previously reported on November 17. Whether seated, reclining or standing, the monopod is an excellent platform for image stabilised binocular astronomy, as it’s very easy to find a supremely comfortable position to conduct observations for all altitudes, from the horizon to the zenith. The lunar images remain sharp, with high contrast and very little in the way of glare evident to my eye. The extra image scale (25%) over the 8 x 42 is immediately appreciated, allowing lunar details to be more easily discerned at a glance. Some brief spells observing star fields in bright moonlight also produced very satisfying results. Suffice it to say that I cannot wait for the Moon to get out of the sky so that I can enjoy the wonders of the winter dark with this little instrument.

I have just one quibble with the 10 x 50; the soft carry case is identical to that which came with the 8 x 42. The case is ideal for the latter but is a little too small for the larger 10 x 50. Not a big deal but it should be said.

The Barr & Stroud 10 x 50 is the ideal astronomy binocular, offering exceptional perfromance at a price that meets most folks’ budgets. It’s solid construction, quality optics and very attractive price makes it an exceptional value in today’s market. Indeed, in an age where it is so very easy to get carried away by gimmicks and clever marketing ploys that pressurize individuals to depart with relatively large amounts of money, it is very reassuring to know that one can acquire this level of performance for a very reasonable financial outlay.

I heartily recommend these binoculars to stargazers everywhere and hope that they will give the reader as much joy as they have given me.

Thanks for reading.

 

Neil English is writing a new book dedicated to the ShortTube 80 achromatic telescope.

 

De Fideli.

A Visual Extravaganza Under Dark Scottish Skies.

Looking east: sunrise over Wigtownshire.

 

The heavens proclaim the glory of God.
The skies display his craftsmanship.

                                                                              Psalm 19:1

 

Contrary to what you may have heard in the past, the British Isles offer many outstanding places to observe the heavens. Sure, we don’t have vast deserts or majestic mountain ranges that ascend for miles into the sky, but we are truly blessed with many sparsely populated regions, where the activities of human civilisation are minimal. Having lived in Scotland for more than half of my life, I have been fortunate enough to discover many fine locations that offer both very dark skies and good seeing conditions. One such region lies in Wigtownshire, in the extreme southwest of Scotland, in the district known as Dumfries & Galloway.

Not far as the crow flies from the Scottish Dark Sky Observatory, situated to the north of the Galloway Forest Park, the site offers nearly unobstructed views of the heavens from zenith to horizon in all cardinal directions. The gardens are decorated with beautiful beech and cherry trees, the leaves of which vibrantly radiate the rich colours of autumn during sunny spells. By day, there are many places to visit nearby, including the little town itself, famous for having more bookshops than any other in Scotland, as well as rugged country walkways and picturesque seaside villages that adorn the coastline all around the peninsula.

The nearby fishing village of Portpatrick on the west coast of the Rhins of Galloway.

 

During the four nights we spent there in mid-October 2018, we were fortunate enough to encounter long clear spells every night, and with a low-lying harvest Moon setting early, the skies became wonderfully dark, allowing the full glory of the northern heavens to manifest itself. Owing to its location near the sea, the skies here are regularly swept clear of particulates, which makes for exceptionally transparent conditions, ideal for astronomy.

The shores of Loch Ken, near Castle Douglas.

I took along my best travel ‘scope; a modified 130mm f/5 Newtonian, which has proven superior to a string of other, more traditional, travel ‘scopes I have enjoyed in the past, including a TeleVue 76 & 102, a classic TeleVue Genesis Fluorite F/5,  a PrimaLuceLab ED 90 and a variety of smaller Maksutovs in the 90 to 102mm aperture class. With very generous light grasp and resolution, the 5.1” Newtonian has proven to be an enormously versatile instrument for exploring the landscape by day and by night. I also brought along my recently acquired Barr & Stroud 8 x 42 roof prism binocular to soak up ultra-wide field vistas of the northern heavens that perfectly complement the more restricted field offered up by the telescope.

Plotina: the 130mm f/5 Newtonian travel ‘scope used to explore the northern heavens.

 

To get an idea of how good the skies are here, 8 members of the Pleaides are clearly visible to my average eyes once it rises to a decent altitude, as is the North American Nebula in Cygnus. In addition, a string of Messier objects in Auriga, Perseus, Cassiopeia and Pegasus are much more easily discerned visually than at home. The glory of the Milky Way, snaking its way roughly from east to west, is intensely bright here, so much so that at times I considered it a form of light pollution lol.

The patch of land where most of the observations were conducted, looking northeastward.

 

Clear skies come and go here all the time. For a few hours, they remain resolutely clear, then the clouds roll in off the Irish Sea, occluding the celestial realm for a spell before being swept away to the east. Although many calm spells occur at this site, watching the direction of smoke billowing upwards from the chimney of the cottage’s wood-burning stove, indicates that the prevailing winds are gentle and southwesterly in direction. In addition, the site is very quiet and peaceful, naturally arousing deep spritual feelings from within. In the wee small hours, only the sound of gentle breezes whistling through the trees breaks the silence.

The first night proved profitable for outreach. Although this was our third trip to the cottage, a change of ownership occurred earlier in the Summer, when a married couple with a young family underwent a home-coming of sorts, returning to the land of their youth. Their two boys instantly struck up a friendship with our lads, and so the evening started by showing them the rugged beauty of the Moon, now at first quarter phase, through the little telescope. Nearby Mars proved a little underwhelming though, as by this time it had receded greatly from the Earth in comparison to how it looked in August last, but they were still thrilled to see its little pink disk broiling in the low altitude air close to the southern horizon.

After enjoying some supper, I ventured out later in the evening when the Moon had set to show our guests, which now included the boys’ father, some of the showpieces of the deep sky with the 8 x 42 binocular and the telescope. The Andromeda Galaxy and its spooky satellite systems – M32 and M101 – made a big impression on them. For these objects I used the 25mm Celestron X-Cel LX eyepiece delivering a clean 2.3 degree true field at 26x. The dad was deeply moved with the Perseus Double Cluster, as were his sons, but I also gave them an opportunity to see M57 in Lyra and the beautiful colour-contrast double star, Albireo, well positioned high in the northwest sky in Cygnus. The owner was very surprised to learn that the telescope I had brought was quite inexpensive and seemed genuinely interested in acquiring one for himself.

The telescopic views were complemented by carefree scanning of the heavens with the 8 x 42 binocular. Showing them where to point the instrument, they gasped with sheer delight as they beheld the riot of stars centred on Alpha Persei, now high in the southeast, as well the way the binocular broke up the frothy Milky Way into myriad pinpoint stars against a coal-black sky. I don’t think the father had realised just how good the skies over his farmstead could be. I made it clear to him that he was very fortunate indeed to have such outstanding natural beauty on his doorstep!

The second day of our trip (October 16) started cloudy with some light drizzle, but as the day progressed the rain ceased and the clouds began to break up to leave a fine evening. I waited until the Moon was out of the sky before setting up the 130mm f/5 to observe M 15 in Pegasus. Having the 8 x 42 binocular hanging around my neck at all times, I was able to quickly zoom in on this fairly bright Messier object, first with the binocular, which presented the structure as a reasonably bright fuzzy star. By using averted vision, the size of M15 nearly doubled in size to more than half the size of the full Moon. Using averted vision with binoculars is a new activity for me but it certainly pays dividends! The great darkness and transparency of the air at our observing site enabled the decent light grasp of the telescope to be used productively and I was able to resolve a few dozen of its outlying stars using a 4.8mm T1 Nagler yielding 135x; a very tiny eyepiece by modern standards but a true marvel of optical engineering. Much more compact than M 13, the core of M 15 remained very bright and highly condensed, but as it floated through the huge field of view of the eyepiece with its fairly tight eye relief, I brought to mind its prodigious distance; 34,000 light years, far out in the halo of our galaxy.

From there I sped eastwards into Perseus to see how an improved sky would present the large open cluster M 34. Again, the binocular was used to locate the cluster first before centring it in the field low power (26x) field of view of the telescope. Even at 26x, the view was very impressive, with a sprinkling of 60 or so stars haphazardly strewn across a field of view roughly the same as the full Moon. The view was immeasurably improved using my trusty Parks Gold 7.5mm eyepiece (87x) which framed the entire cluster with just a little room to spare.

At 22:36UT I recorded an extraordinarily bright fireball, which was extremely long-lived, darting across the sky from north to south. At its brightest it was maybe twice the size of the full Moon and took approximately 4 seconds to fizzle out.

The 8 x 42s also made light work of tracking down the rather elusive face-on spiral galaxy, M 33 in Triangulum. At 26x in the 5.1″ the galaxy took on a ghostly cast in an interesting field of mostly 8th and 9th magnitude stars. To my eye, it looked for all the world like a planetary nebula more than a galaxy, with a slight greenish hue. Still, the extra darkness and improved transparency of the Wigtwonshire sky certainly added to the enjoyment of the view. I was particularly delighted by how well the little roof prism binocular could pick it up, as this object has a notoriously large size and low surface brightness.

With the time rapidly approaching local midnight, it was time to have a closer look at the magnificent Pleiades asterism in Taurus. For this target, the binocular proved the superior instrument, with its low power and generously wide field of view (7.33 angular degrees). Riding high in the eastern sky, it was quite simply stunning! Much of the cluster appeared to be enveiled in a fog-like nebulosity which gave it a rather life-like translucent appearance to my eye. No words come close to describiing the full glory of this extraordinary natural beauty and I spent several silent minutes just enjoying the spectacle.

I ended the vigil that evening by examining just a few double stars in the telescope. My notes from earlier years showed how good the site is for conducting high-resolution double star observing during the Summer months, but I wasn’t out to break any records. Suffice it to say that systems that have traditionally been described as ‘difficult’ in more conventional grab ‘n’ go telescopes are beautiful and easily rendered in this instrument. For example, I achieved a most excellent split of the triple system, Iota Cassiopeiae, now very high overhead, using my favourite tools in this telescope for carrying out such work; a 7.5mm Parks Gold coupled to a Meade 3x achromatic Barlow yielding 260x. The three stars were pinpoint sharp (a result of precise collimation using my Cheshire) and the subtle colour differences easily discerned to my eye. Almach (Gamma Andromedae) was gorgeous too at the same power, as was Polaris A & B and  Delta Cygni A & B.

Simply superb for tight double stars; the author’s 7.5mm  Parks Gold eyepiece coupled to a 3x Meade achromatic Barlow lens.

 

Newtonian telescopes are excellent diviners of double stars, an attribute that still appears to be lost on many contemporary amateurs. I have cultivated a theory to explain this anomaly. I suspect that many refractor enthusiasts (onlyists?), accustomed to the hassle-free observing with small refractors, never properly learn how to collimate Newtonians(it does take a while to fully learn the skill!) and, as a result, they attribute their mediocre performance in this regard to other factors and not to badly aligned optics. It’s just a hunch, but I have good reasons to believe it!

With the Moon setting later in the evening of October 17, I gave the telescope a rest and just enjoyed the 8 x 42 binocular. Up until fairly recently, I had forgotten just how wonderful it is to use such a small and lightweight instrument on its own terms. My first target was the magnificent Double Cluster (Caldwell 14) now very high in the eastern sky, as well as the less well-known open clusters surrounding it including the fairly large Stock 2(~1 degree), found by following a curvy chain of stars northwards, away from the twin clusters, and the small and compact (~10’) NGC 957. The binocular view provides a unique perspective that just can’t be replicated in even the smallest rich field telescope.

From there I sought out Kemble’s Cascade, tucked away under Perseus in neighbouring Camelopardalis. A steady hand is a great virtue when deriving the most out of this remarkable linear arrangement of mostly 8th and 9th magnitude suns. Though the cluster is well seen from my home further north, the darker and more transparent skies here made it all the more thrilling to study. For me, binoculars are almost always about hand-held instruments, but I found it beneficial to steady the view on the wooden farm gate on the grounds, where I was able to distinctly make out the small foggy patch denoting the open cluster NGC 1502, where the cascade abruptly terminates.

A little achromatic pair.

 

Though not the best season to explore M 81 and M82 in Ursa Major (they are much higher in the sky in the Spring as seen from the UK), they were very easy to locate in the 8 x 42 binocular despite the constellation’s fairly low altitude in the northern sky at this time of year.  Considerably more challenging though was M51, the famous Whirlpool Galaxy, across the border in Canes Venatici, and even lower down in the sky, which presented in the binocular as a slightly elongated fuzzy patch.

Over in the west, about 8 degrees due south of golden Albireo and on the border with Sagitta, the Coathanger (Collinder 399) asterism was also a joy to observe with the 8 x 42, albeit ‘upside down’ in comparison with the low-power view in the 5.1” reflector. The sense of unity among the stars which comprise the asterism is a pleasant illusion however, as they are actually situated at varying distances from our Solar System. Also nearby, the binocular made light work of tracking down the large planetary nebula M27, which looked like a tiny, incandescent cloudlet against a sable background sky.

Later in the evening, the large and prominent constellation Auriga, represented by a great pentagon traced out on the sky, gained altitude in the east. At its heart, the 8 x 42 presented the three open clusters M 36, M 38 and NGC 1893 very well indeed as foggy patches in a beautiful, rich field glistening with myriad, faint Milky Way stars. M 37 was easy too, just east of the pentagon. About one third of the way in a line from M38 to brilliant yellow Capella, the binocular also swept up the small and faint open cluster, NGC 1857.

As local midnight approached, Taurus had risen to a decent height and it was the ideal time to examine it with the binocular. The generous 7.33-degree field of the 8 x 42 presented the Hyades asterism in all its wondrous detail. Brilliant orange Aldebaran(not a true member however) proved to be a mesmerizing sight, as did the many binocular doubles the instrument picked up immediately to its west. Again, telescopes can’t really do justice to this asterism, as its full glory is hopelessly lost in their much smaller field of view.

As a test, I tried my hand at locating the rather elusive M1 (Crab Nebula) centred on a spot roughly 1 degree to the northwest of the bright blue-white star, Zeta Tauri. I was unable to see anything of this Messier object just hand-holding the binocular, but I believe I achieved success by steadying the view a little on the wooden fence post. Considering that M 1 is a rather lacklustre telescopic object in small and medium aperture ‘scopes, just glimpsing the tiny, roughly 6’ x 4’ smudge was considered a notable visual achievement by this author!

I ended the binocular vigil by welcoming Gemini over the eastern horizon. Though not quite visible to the naked eye owing to its very low altitude at the time of observation, my tiny 42mm ‘double achromat’ made light work of picking up the lovely telescopic open cluster, M35, at the northwestern-most foot of the constellation, together with the fainter open cluster NGC 2158 just next door. This ‘double cluster’ of sorts will look far more impressive when the constellation gains altitude in the coming months.

By half past midnight local time, and with more of the lights from the small, sleepy town nearby having been extinguished, the sky became maximally dark. “The constellations look just like they do in my observing guide!“ I wrote in my logbook.  At the zenith stood majestic Cassiopeia, and ahead of it, Cygnus, now sinking low into the west. Behind it, as if in some kind of grand procession, came Perseus, Auriga, Taurus and mighty Orion looming large in the southeast. The view was so awe-inspiring that I set my binocular aside and just sat in silent contemplation of the lightshow presented to my weary eyes. This, I thought to myself, is the view of the heavens that was accessible to the vast majority of people who ever lived. It had a singular beauty all of its own; just the way the Creator intended it!

And that’s where it all ended on the penultimate night of our stay.

After spending our last day out at Portpatrick(October 18) and a nice family dinner at Bladnoch, we returned to the cottage after dark and to rather more overcast skies. I did venture out to have a look at the waxing gibbous Moon which culminated in the south about 20:00UT when the clouds began to break up once again. Though not a dedicated lunar observer by any measure,  the telescope delivered lovely high contrast images at low and medium powers (up to about 135x). The Moon would not be setting until much later this evening however, so I set the telescope up for work that would not in the least be affected by the encroach of lunar light; double stars.

Plotina; ready for a night of casual double star observing.

 

For this work, I charged the instrument with my Parks Gold 7.5mm eyepiece coupled to a good 3x achromatic Barlow lens yielding 260x and off I went to assess how well the telescope would do this evening. After obtaining lovely splits of Delta Cygni, Iota Cassiopeiae and Epsilon 1& 2 Lyrae, I knew conditions were very good indeed; as they are in many other places in the British Isles. The 1.5″ pair, Pi Aquilae, was a little bit more suspect though, owing to its much decreased altitude in the western sky at this time of year.

A little later, I enjoyed text-book perfect images of Gamma Andromedae, its beautiful colour contrast never faiing to bring a smile to my face. The stellar images in this telescope hardly ever fail to impress. It’s a combination of perfect collimation, modest aperture, good thermal management, adequate light baffling and high-quality optics, but it also requires clear and steady skies, which are accessible to far more observers than has been reported in the recent forum literature.

Two systems in Perseus also proved profitable; Epsilon Persei, with its very faint close-in companion which, of itself, acted as an excellent test of telescopic contrast, and Eta Persei, a lovely wide open, colour contrast double, with a magnitide +3.5 orange supergiant primary and turquoise secondary shining much more feebly at magnitude +8.5.

Finally, this was the evening that I also obtained my first clean split of the tricky system, Theta Aurigae, which was perfectly resolved in the 5.1″ reflector at 260x; my first such splitting of the new season! The difficulty with such a system is the great brightness differential between the components (+2.6/ +7.5) and close angular separation, but the 5.1″ f/5 Newtonian managed it perfectly well as it has done in previous seasons.

I made a quick sketch of how it appeared in the telescope at 22:25 UT (shown below).

An old friend: Theta Aurigae.

 

Note added in proof: On the frigid evening of October 29 at 22:15 UT, in an ambient temperature of -2C, this author took advantage of excellent seeing (Ant I) to obtain his second perfect split of Theta Aurigae of the season using the 130mm f/5 reflector at 260x from his home in rural central Scotland. The Airy disks were round as buttons with a single faint Fraunhofer diffraction ring. Almach (Gamma Andromedae) was spell-bindingly beautiful and calm in the same telescope when examined just a few minutes later.

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Concluding Comments:

The intensely curious & friendly little hens on the farmstead that cannot help but entertain the visitors!

 

It was good to get away.

The weather was settled and mild throughout, with only the occasional spot of rain. All four nights proved to be good and clear for long spells and the days were filled with worthwhile family activities out and about. This is a great place to observe the preternatural beauty of the night sky, tucked away as it is far from the cities and their horrendous light pollution.

We will certainly be visiting again!

We packed up the car early next morning with the intention of getting a good head start on the road back north. Inevitably on such trips, we always leave stuff behind. Sure enough, the owner emailed us later the same evening informing us that he had found a ” telescope cover” aka my flexi dew shield, and a set of earrings belonging to my wife. The boys were not immune to absent mindedness either, as a pair of ankle socks were found inside one of their beds. He kindly offered to post the items back in the week ahead. On Wednesday, October 24, a large yellow package arrived at our home with the said items inside. I emailed him back later the same evening, thanking him for his prompt attention to this matter but also with the offer to reimburse him fully for his efforts. He replied that there was no need:

“The astronomy lesson with the boys and myself was payment enough!”

Fair is fair I suppose lol!

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Appendix: Olber’s Paradox Redux: A Brief Mathematical Treatment of the Consequences of a Dark Sky at Night.

 

In 1823, the German physician and astronomer, Heinrich Wilhelm Olbers (1758-1840) considered an interesting question; why is the night sky dark? At the time, many scientists considered the Universe to be either infinitely old or large, or both. But Olbers considered the logical consequences of this pre-supposition. In an infinite Universe, Olbers reasoned, every line of sight should eventually meet up with the surface of a star. So, the night sky should actually look like the surface of a star. Indeed, the whole sky would appear the same; uniformly bright as a consequence of an infinitely large number of stars. This interesting conundrum is known as Olbers’ Paradox.

A system of stars (or galaxies) arranged in concentric shells with the Earth at the centre.

 

Words can only go so far though, so let us consider the problem from a simple, quantitative point of view.

Suppose we start dividing up the Universe into an infinite number of concentric shells, illustrated in the sketch I’ve made above(apologies for the crudeness of the sketch, as I’m no artist lol), centred on the Earth, with each shell having a uniform thickness, dr. Thus, the volume of each shell (dV) would be the surface area of a sphere of any considered radius r multiplied by its thickness(dr);

So dV = 4πr^2dr.

Now, if there are n stars per unit volume (denoted by asterisks in my sketch), then the total number of stars, N, in each shell will be:

N = 4nπr^2dr.

It is easy to see that the number of stars per shell will scale as r^2. However, the irradiance of each star will fall inversely as r^2, which has a cancelling effect on the overall brightness of each shell and so each shell ought to be uniformly bright.

We must slightly amend the above conclusion, as each star actually has a finite size, with the result that the nearer stars will eventually occlude the light from the more distant stellar members. Still, this would not happen until the entire sky looks as though it is covered with stars. And that returns us to the original conclusion.

Nota bene: The reader will note that each star in the diagram could be replaced by a galaxy with precisely the same consequences!

Let’s now look at possible ways to reconcile Olbers’ Paradox with what we actually witness when the Sun falls out of the sky.  For example, we might consider if the absorption of distant starlight by interstellar (or intergalactic) dust might provide a means of escaping the paradox. Unfortunately, if the Universe is infinitely old, or even existing for just a very long time (say for argument several orders of magnitude older than 13.87 Gyr), then we would expect that such dust particles would have absorbed enough radiant energy to raise their temperature to the same temperature as the surface of a star. And even if it became hotter than the surface of a star, it would merely radiate the excess energy, which the stars would absorb. The consequences are the same though; the sky would look uniformly bright in all directions.

Now consider an expanding Universe, where light is redshifted. In such a case, the energy of each photon of light would decrease as a function of radius, r, so this would help attenuate the brightness of each shell considered above. What happens when we add up individual contributions from each shell? At any fixed radius, the brightness would scale as ∫dr/r, which computes as the natural logarithm of r, i.e. ln(r). But one can readily see that if we choose an arbitrarily large radius, even the quantity ln(r) can become very large indeed, so not ultimately helping us to resolve the problem.

One way out is to consider a Universe that is not infinite in extent, so we can cut off our integral at that finite radius. But there is one other way to achieve the same result, by considering a Universe that has a finite age. Let this age be denoted by t. In this scheme of events, we will only observe stars that are close enough for their light to have traversed the Universe at the speed of light, c. Thus, the radius of that Universe is simply ct. In either scheme; a finite age or finite size, there will exist a limit to the number of concentric shells that could contribute to the brightness of the sky and so the paradox can be resolved!

I find it amazing that from the simple observation that the sky is dark at night, we can arrive at a rather profound conclusion. That said, this analysis cannot, by itself, distinguish which of those scenarios, finite size or finite age (or even both), is the ultimate reason for the darkness of the night sky, but its consequences raise other philosophic/theological questions; if the Universe had a beginning, which has long remained the consensus amongst cosmologists, who or what brought it into existence?

You can’t have an uncaused cause!

To my mind, there is little doubt that the God of the Bible provides the best and most complete answer.

 

In the beginning God created the heavens and the earth.

Genesis 1:1

 

Thus says the Lord who stretches out the heavens, lays the foundation of the earth, and forms the spirit of man within him.

Zechariah 12:1

 

Neil English discusses the work of hundreds of astronomers from the annals of history in his new book, Chronicling the Golden Age of Astronomy.

 

De Fideli.

The Venerable ShortTube 80 Refractor.

The author’s versatile ShortTube 80mm f/5 achromatic telescope.

 

In my next literary project, I’ll be dedicating my time to discussing the venerable ShortTube 80 f/5 achromatic refractor; an affordable, ubiquitous telescope that enjoys a 30 year + pedigree.

 

Tune in soon to find out why such an instrument deserves a book-length treatment……….

 

De Fideli.