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.

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.

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.

Using Small Newtonians in a Terrestrial Setting.

Snug as a bug in a rug, ken.

 

As I discussed at length in previous blogs, my chosen grab ‘n’ go telescope of choice is a high performance Newtonian reflector with an aperture of 130mm (5.1 inches) and focal length of 650mm (f/5). The telescope has an excellent Skywatcher primary mirror, the original secondary mirror was replaced by a higher quality unit with a slightly smaller semi-major diameter of 35mm, yielding a very modest central obstruction of just 26.9 per cent. Both mirrors received new, state-of-the-art ultra-high reflectivity coatings to increase both light throughput and image contrast. The interior of the tube is lined with cork and covered with matt-black flocking material to minimise stray light and more effectively deal with thermals. Best of all, the entire outlay was very economical, setting me back just a couple of hundred pounds.

In field tests, the instrument, once collimated and acclimated completely outclassed more traditional grab ‘n’ go telescopes, including a high-quality 90mm apochromatic refractor on lunar and planetary targets, double stars and a veritable pantheon of deep sky objects. In a series of more recent tests, it was shown to give better daylight images than a 5″ f/12 classical refractor and closely approached its light gathering power and resolution on a variety of nighttime targets.

The instrument is very light weight and completely stable on a sturdy Vixen Porta II alt-azimuth mount equipped with slow motion controls. The instrument is very easy to collimate using either a Chesire eyepiece or laser collimator and perfect results can be achieved in a matter of seconds. Its low mass ensures that it acclimates very quickly to ambient, allowing me to engage with celestial targets very quickly. For low and medium power views (up to 80x or thereabouts), the telescope can be used more or less immediately. For higher resolution targets, it’s fully equalised in about 30 minutes, even on the coldest nights. Tucked away in its lightweight aluminium carry case, it has travelled to many destinations in the British Isles where its excellent optics has enabled it to perform flawlessly.

As I explained earlier, I do as much daytime observing as I do at night and in this capacity, the telescope has thrilled its owner with crisp, high resolution details of the Creation, especially at powers in excess of 100x, where traditional spotting ‘scopes with their smaller apertures, rapidly run out of light. This is all well and good but Newtonian reflectors produce images that are both up-side down and right-left reversed, making traditional kinds of nature spotting problematical. Try observing a distant ship at sea using a Newtonian to see what I mean. These limitations led me on a quest to acquire and test a variety of products that promised to remedy this problem.

Product 1: SkyWatcher 10mm Erecting Eyepiece

The SkyWatcher 10mm Erecting Eyepiece.

 

Costing about £25 plus shipping, the unit also comes with an extension tube, which was not found to be necessary. It works by using an internal roof prism sandwiched between the field lens and eye lens. The eye lens is anti-reflection coated but its field lens is not. Examining the roof prism also indicated that it was not coated.

The coated eye lens of the SkyWatcher erecting eyepiece.

The field lens has no anti-reflection coatings.

 

The consequences of not coating all the optical components, even if perfectly executed are three fold; first contrast will be diminished, secondly, it will cause ghost images when observing bright objects. Finally, it will lose light producing images that are a fraction dimmer than conventional eyepieces with good coatings.

Optically, it delivers a power of 65x and the image is reasonably good and sharp, with a nice, hard field stop. It is very small and lightweight but it lacks the punch of a regular eyepiece that possess either fully coated or multicoated lenses and performs poorly when imaging bright daylight objects such as water reflections etc. Examining the bright planet Venus one evening, the eyepiece revealed prominent ghosting in the image which I found distracting. If you are looking for the best images from daylight tests, this is not a product I would recommend.

Product 2: Roof-prism based image rectifiers

Two such devices were purchased; one unit called “Angeleyes” and the other marketed by “Datyson”. Both devices enable one to use eyepieces interchangeably and cost about £30 plus shipping.

The Angeleyes and Datyson image rectifiers.

 

Both are 4.5 inches long, with only the upper bodies protruding above the focuser. Both have a multicoated Barlow lens placed ahead of an internal roof prism. The selected eyepiece is mounted inside the upper body and secured with a single screw.

The multi-coated Barlow lens at the bottom of the image rectifiers.

 

In what I consider to be rather nefarious marketing, one of the units was advertised as delivering a 1.5x amplification, while the other stated that the Barlow delivered 2x. In fact though, both products were identical apart from their labelling. Worse still, the amplifaction was more like 3x on both units. Examining the internal roof prisms showed that they were uncoated.

All eyepieces tested came to focus with these units. The lowest power oculars tested; a 32mm Plossl and 25mm Celestron X-Cel LX produced images that were quite good, but in order to see the full field of view your eye must be placed about an inch above the eyelens. In other words, the eye relief with these units is huge! This was not found to be an issue in and of itself, and indeed made the experience very relaxing. Still, they did not deliver the low power views that I was enjoying using these eyepieces on their own; they amplified the image too much. Instead of having a low power of 20x and 26x respectively, these units were giving images of the order of 60x; not low enough to enjoy wider fields of view during daylight hours.

Eyepieces are mounted into the upper stage of the image rectifiers.

 

Testing these units with higher power eyepieces showed that they produced far too high magnifying powers that were not as sharp as the equivalent eyepiece at the same effective focal length. This was confirmed in nightime tests, where one of the units did not resolve Epsilon 1 & 2 Lyrae as well as a normal high power eyepiece. Image sharpness was definitely compromised.

Though certaiinly useful, I would not recommend either of these units to those looking for the best daylight performance from a small Newtonian telescope.

Product 3: The Vixen Terrestrial Image Adapter

Schmokin; the Vixen terrestrial image adapter.

 

The Vixen terrestrial adapter was purchased from an authorized Vixen dealer within the UK. Costing £80 delivered, the unit is a three lens system and does not employ roof prisms. The product is very well engineered and executed in a quality, all-metal body. It has a modular design, with three sections that thread into each other. It was fun taking it apart. Examining all the lenses on either side of the various segments showed clear blooming. The lenses are all anti-reflection coated. The device is about seven inches long.

The top lens showing anti-reflection blooming.

The bottom lens showing blooming from anti-reflection coatings.

 

Like the previously discussed units, the Vixen adapter allows one to insert any eyepiece into the upper stage. But unlike the fomer, there is no amplification of the image, so the magnification you get from the native eyepiece is preserved using this device. Only 1.25″ eyepieces can be used with this unit.

Testing the device out on daylight targets, the Vixen unit delivered crisp, clear images across a field that maxes out at  ~1.5 angular degrees. Since my preferred low power eyepiece for the 130mm f/5 Newtonian is a 25mm Celestron X-Cel LX (26x), this results in a reduction in the true field available to the native eyepiece but it was still wide enough to satisfy this tester.

At the telescope; the Vixen adapter with the Celestron 25mm X-Cel LX eyepiece attached.

 

Like the prism-based image rectifiers, the Vixen unit has very large eye relief, with the result that you have to move your eye above the top of the low power eyepiece to see the full field. I found this arrangement to be very comfortable.

The Vixen unit produced excellent images with higher power eyepieces, including an 11mm ES 82, a Park Gold 7.5mm, a 4.8mm T1 Nagler and a 2.3mm Celestron X-Cel LX, delivering powers between 59x and 283x.The shorter the focal length of the eyepiece, the closer one has to place one’s eye above the eye lens. Comparing the views with the eyepieces used alone, there was very little light loss, with image sharpness and contrast remaining very high.

Switching to nightime use, examination of a bright waning gibbous Moon with the Vixen unit produced very satisfactory results. The lunar regolith was razor sharp at all magnifications between 26x and 283x and I could also confirm that the maximum true field delivered was 3 full Moon diameters, or about 1.5 angular degrees, as previously estimated. A brief test on Epsilon 1&2 Lyrae with the 2.3mm Celestron X-Cel LX ocular delivered much sharper images of the four components. Optical quality is clearly superior to the roof prism-based units previously described.

Based on these tests, I am very happy to recommend the Vixen terrestrial adapter to prospective buyers, as it will deliver very good, clean images of daylight targets in their natural orientation. That Vixen has developed and brought this product to market suggests that there is some demand for terrestrial viewing using small Newtonians. Why create such a high quality product if there is no demand for it?

Notes on field use:

Being accustomed to using the slow motion controls on the Vixen Porta II mount using eyepieces that naturally invert the image in Newtonian mode, it takes quite a bit of getting used to learning how to accurately manoeuvre the telescope using the same slow motion controls when viewing in terrestrial mode. This comes with the territory. Like everything else, practice makes perfect! Though the adapter looks awkward, it is very easy and comfortable to use. Close focus distance is ~ 20-25 yards.

Independent verification of these findings

I found one online review of the Vixen terrestrial adapter, which affirms the general findings of this tester;

Tried it tonight on the Moon. I thought it performed quite well. It made no major differences to the views through my 32mm and 20mm TV plossls. The image was exactly the orientation I see by naked eye and binoculars – just what I wanted! It was funny, however, moving the scope. I have trained myself well, so I kept heading the wrong direction :lol:. But I got the hang of it. Next to try it on a starhopping exercise. I’ll wait for dark skies.

Source here.

Comparison with conventional spotting telescopes

Preamble: Please consider this review of the Celestron 100mm aperture ED spotting scope. The reader is encouraged to consider its specfications, including weight, complexity of the design, magnification range, colour correction, twilight factor, field of view, close focus distance and cost. The reader will note that this is one of the more economical models on the market; the equivalent premium products are much more expensive.

Let’s compare the specs for a 130mm f/5 Newtonian and the Celestron 100ED spotter

                                              Newtonian                                                       Refractor

Aperture                               130mm                                                              100mm

Resolving power                   0.89″                                                                 1.14″

Colour correction               Fully apochromatic                                 Pseudo apochromatic

Twilight  factor                               58                                                               46.9

Field of view (max)                     1.5 degrees                                               1.9 degrees

Magnification range                      26-300+                                                        22-67x

Close focus distance                      20-25 yards                                                  25 yards

Length                                              23.5″                                                                 20″

Weight:                                           3.8 kg                                                              2.52kg

Cost:                                             ~£350                                                                £1,180

Interchangeable eyepiece           yes                                                                   no

 

You can see at a glance that the Newtonian will offer brighter, higher resolution images at high magnifications than the ED spotter. It’s not rocket science. Think pixels. The 130mm has more ‘pixels’ than the 100mm ED spotting ‘scope. The Newtonian will also work considerably better in low light conditions (better twilight factor) compared with the refractor. I especially appreciate this during the very short days of winter, where light is often at a premium here at 56 degrees north latitude. It was very noticeable last winter when I was conducting tests comparing a 90mm ED refractor and the130mm Newtonian.

The spotting ‘scope is more rugged than the Newtonian but that’s because it must be by necessity; it has to protect all of the components that make it work well. No such fussing is needed with the Newtonian, which can be knocked about and whipped into perfect collimation as and when required .It’s the ultimate low-stress ‘scope! Best of all, the price differential is huge. I’ll leave it up to the reader to decide if the 100mm ED spotter represents genuine value for money, but I can say with certainty that the Newtonian most definitely is.

Having said all of this, for many objects I view during the day, an erecting adapter is quite unnecessary and when I don’t need to use one, I don’t. For night use, the Vixen terrestrial adapter sits pretty in its box. I’m happy with a topsy-turvy cosmos lol.

Moral of story: Improvements are costly!

Neil English explores the history of four centuries of  visual telescopic astronomy in his new book; Chronicling the Golden Age of Astronomy.

 

Postscriptum:October 23 2018

After conducting all of the above tests using the various image-erecting  devices, I found this recent thread on the same topic. The reader will note that some of the posters have conducted their own tests which affrm the conclusions I have drawn in my own work. See here for full details.

Thank you for reading!

 

De Fideli.

Chronicling the Golden Age of Astronomy: A History of Visual Observing from Harriot to Moore.

 

This is an excellent book and will complement Ashbrook’s Astronomical Scrapbook and therefore have wide appeal to both amateur and professional astronomers.

Wayne Orchiston, Professor of Astrophysics, University of Southern Queensland, Australia.

 

Book Content:

Introduction & Acknowledgements

  1. Thomas Harriot, England’s First Telescopist
  2. The Legacy of Galileo
  3. The Chequered Career of Simon Marius
  4. The Era of Long Telescopes
  5. Workers of Speculum
  6. Charles Messier; the Ferret of Comets
  7. Thomas Jefferson and his Telescopic Forays
  8. The Herschel Legacy
  9. Thinking Big: The Pioneers of Parsonstown
  10. The Astronomical Adventures of William Lassell
  11. Friedrich W. Bessel: The Man who Dared to Measure
  12. W.H Smyth: The Admirable Admiral
  13. The Stellar Contributions of Wilhelm von Struve
  14. The Eagle-Eyed Reverend William Rutter Dawes
  15. The Telescopes of the Reverend Thomas William Webb
  16. The Astronomical Adventures of the Artistic Nathaniel Everett Green
  17. Edward Emerson Barnard, the Early Years
  18. William F. Denning; a Biographical Sketch
  19. A Modern Commentary on W.F. Denning’s “Telescopic Work for Starlight Evenings (1891)”
  20. The Astronomical Legacy of Asaph Hall
  21. The Life and Work of Charles Grover(1842-1921)
  22. Angelo Secchi; Father of Modern Astrophysics
  23. John Birmingham, T.H.E.C Espin and the Search for Red Stars
  24. A Historic Clark Receives a New Lease of Life
  25. A Short Commentary on Percival Lowell’s “Mars as the Abode of Life”
  26. The Great Meudon Refractor
  27. A Short Commentary of R.G. Aitken’s “The Binary Stars”
  28. S.W. Burnham; a Life Behind the Eyepiece
  29. Voyage to the Panets: The Astronomical Forays of Arthur Stanley Williams( 1861-1938)
  30. Explorer of the Planets: The Contributions of the Reverend T.E.R. Philips
  31. Highlights from the Life of Leslie C. Peltier
  32. Clyde W. Tombaugh; Discoverer of Pluto
  33. A Short Commentary on Walter Scott Houston’s “Deep Sky Wonders”
  34. A Short Commentary on David H. Levy’s  “The Quest for Comets”
  35. George Alcock and the Historic Ross Refractor
  36. What Happened to Robert Burnham Junior?
  37. The Impact of Mount Wilson’s 60-inch Reflector.
  38. Seeing Saturnian Spots
  39. John Dobson and His Revolution
  40. The Telescopes of Sir Patrick Moore (1923-2012)
  41. A Gift of a Telescope: The Japan 400 Project

Appendix:

Achievements of the Classical Refractor: A Timeline

Index

 

Available now for pre-order!

 

Thankyou for waiting!

 

De Fideli.

5-inch Shootout: 5″ f/12 Refractor vs a 5.1″ f/5 Reflector

Battle o’ the 5-inchers. Tiberius (laevo); a 127mm f/12 achromatic refractor versus Plotina; a 130mm f/5 Newtonian reflector.

 

Introduction: Many telescope reviews conducted on forums or in magazines only assess a single instrument, namely the one under consideration, entirely on its own terms. But while such informaton can be useful, particularly if a fault is discovered, it can be somewhat misleading if no other instruments are compared with it. Take for example, a top drawer 60mm refractor, which produces excellent images within the remit of its aperture, but when it’s compared to a slightly larger telescope of average quality, it begins to show its limitations and the tester gains a much more balanced view of its strengths and weaknesses.

I find myself thinking this way when evlauating all the telescopes that pass through these parts. Such tests are very important and completely warranted. For example, I was once very much enamoured by an expensive 4-inch F/5 Televue Genesis fluorite refractor but quickly fell out of love with it once I compared it to an even more expensive Televue 102 apochromat. In turn, the latter telescope was found to be slightly inferior to a SkyWatcher ED 100 f/9 refractor costing far less than either of the Televue refractors, which left a very bad taste in my mouth, making me deeply suspicious of the claims proferred by those who market so-called ‘premium’ telescopes, as well as the forum fanboys who apparently cannot see beyond them.

But sometimes it pays dividends to compare good telescopes from different genres too, such as my discovery that an 8-inch f/6 Dobsonian proved superior to a 7-inch f/15 Maksutov Cassegrain, even though the former was less expensive. Clearly, you don’t always get what you pay for! You need to find the truth for yourself.

In this capacity, I decided to compare and contrast the capabilities of two very different telescopes of similar aperture; a 127mm f/12 achromatic refractor and a 130mm f/5 Newtonian reflector costing many times less.  I have described the capabilities of this refractor in many previous blogs (now archived by the author). I have retained it as an excellent example of a historically important class of telescope that allowed amateur and professional astronomers to make great strides in understanding the Universe around them and which continues to provide excellent insights into their considerable capabilities. Interested readers will find a veritable treasure trove of classical achromat ‘culture’ in the author’s up-and-coming book, Chronicling the Golden Age of Astronomy, due out in late 2018.

But having said all of this, the Newtonian reflector has been terribly neglected by a generation of amateurs that seem to know the price of everything and the value of nothing. Unwilling to take their cue from the professional community, who have long left the refracting telescope behind in favour of the enormous advantages offered by modern reflective optics, they continue to disseminate misleading or downright false information to unsuspecting newcomers to the hobby, who are subsequently led astray in such a way that their progress as observers becomes severely stunted. That’s why it’s important to continue to question received opinion. If we stop questioning, we quickly become part of the herd culture that so typifies contemperary amateur astronomy.

The instruments compared: The refracting telescope is a high-quality neo-classical instrument (doublet objective) with an aperture of 127mm and focal length of 1524mm (so f/12). The optical tube assembly is about 1.8m long and weighs in at 40 pounds. It sports a fully multi-coated object glass which passes virtually all the light that passes through it. It has a state-of-the art,  dual speed Moonlite focuser, which is fully rotatable and extremely robust.

The beautiful objective lens on the Istar Asteria 127mm f/12 refractor..

 

The wonderful two-speed Moonlite focuser on the Istar refractor.

Such a bulky instrument requires a substantial mount and even when provision is made for its mounting (with its various counterweights)  it can prove very awkward to use in the field, particularly when the instrument is pointed high in the sky.

The Newtonian, in contrast, even with its dovetail plate and finder attached, is featherweight in comparison. Both primary and secondary mirrors possess quality, high-reflectvity coatings, reflecting 97 of the light incident upon them and with a small 27 per cent central obstruction with its upgraded optical flat, it loses very little light to deliver tack-sharp, colour free images with high contrast. It’s focuser, however, is of the simple, single speed, rack & pinion variety. It needs to be accurately collimated for such testing but this requires just a minute of one’s time to attain perfect results.

The innards of the 130mm F/5 Newtonian reflector.

The simple rack & pinion focuser on the 130mm Newtonian.

 

Test 1: Comparison of the high magnification images in daylight; conducted August 21 2018.

Both telescopes were set up on their mounts (the reflector was mounted on a simple Vixen Porta II alt-azimuth) during a warm, overcast day and the instruments charged with a high magnification (~ 50x per inch). The refractor delivered a power of 277x, while the reflector yielded a magnification of 283x. Both telescopes were aimed at the topmost bough of a Horse Chestnut tree some 80 yards distant and the instruments carefully focused.

Results: Both instruments served up sharp, detailed images of the well-developed foliage. The Newtonian was much harder to focus accurately owing to its fast f ratio(5), in comparison to the refractor (f/12). They were very comparable in terms of image brightness but the reflector showed a consistently better image. It was a shade sharper and completely devoid of chromatic aberration (CA). The refractor did show some CA in comparison, which manifested a faint chromatic fog, lowering image contrast and sharpness.

I called two other visual testers to the telescope; my wife and a next-door neighbour. Teaching them how to focus the telescopes finely, I let them examine the images in both telescopes for a few minutes, eventually enquiring of them which instrument delivered the better high power daylight views.

Their verdict was the same as my own, namely, that the reflector delivered the better image of the tree-top foliage.

Comments: It might have been anticipated that the refractor would offer the brighter image, but CA takes some of the unfocused light and spreads it around the field, slightly lowering the overall brightness of the focused image.

Test 2: Double Star Performance: August 22 2018

Tiberius (laevo) et Plotina; fratrem certamen accendebant.

Wide field performance tests aborted until the Moon was out of the sky. Some double stars were critically examined instead.

Conditions: Brisk southwesterly winds, partially clear, visibility rather poor except near zenith. Temperature + 10C, rather cooler than of late.

Both telescopes were set out to cool from the late evening (19:00 UT) onwards, so completely acclimated to their environments.

4 systems examined at high powers (260x  and 277x on the 130mm f/5 and 127mm f/12, respectively):

Epsilon Lyrae 1 & 2

Delta Cygni

Pi Aquilae

Mu Cygni

Results: Only a brief observing spell possible with by telescopes this evening between 21:00  and 21:25UT as low cloud moved in and made the sky increasingly difficult to navigate. By 22:00 it had all but competely clouded over again.

Both telescopes resolved all four systems well at the powers mentioned above. The breezy conditions and the high altitude of three of the test systems made it very challenging to observe in the refractor owing to its long tube and positioning of the eyepiece very near the ground (a Televue 2-inch EverBrite dielectric diagonal being employed to make observations easier). The same systems proved far more comfortable to observe in the Newtonian, for obvious reasons. The long refractor really needs a massive equatorial mount to do it justice; something I am not interested in pursuing.

The refractor definitely pulled ahead though in terms of ease of focus of the subjects (at f/12 you’d expect that), while using the reflector with its simple rack & pinion focus and f/5 relative aperture was always much more challenging. Indeed, I had forgotten the considerable advantages the classical refractor has over faster systems in this regard. The refractor images showed little in the way of diffraction artifacts, the stellar Airy disks being very tight and round as buttons. Contrast was a tad better in the unobstructed refractor and the images were marginally more stable as judged by their reduced tendency to morph out of perfect focus as they moved across the field. That said, I was very pleased at how well the reflector held its own; the more prominent diffraction rings having no discernible effects on the resolution of these point sources. And while contrast was a shade better in the refractor, I did not judge it superior enough to warrant a discontinuation of my double star adventures with the 130mm Newtonian. Its wonderful comfort is a huge virtue in this regard.

Comments: The CA described in the daylight tests had no effect on the resolution of these test doubles (an observation well borne out by an enormous body of historical literature), although their colours were slightly distorted (yellowed) compared with the Newtonian(which by nature always delivers true colour images). Indeed, the secondary spectrum was only slightly apparent on Delta Cygni A, being quite a bright star. What is more, I felt it added slightly to the aesthetic appeal of the refractor image over the reflector, but this is a completely subjective judgement.

Test 3: Deep Sky Capability: September 6 2018.

The sloth discovers heehaw….ken.

 

Although the last three nights have been excellent for deep sky observing, I decided to leave this test until the evening of September 6 2018, to make sure no moonlight interfered with the observations. Still, the effort was very rewarding and insightful. As you can imagine, these instruments are very different beasts in regard to their demands on eyepieces. At f/12 even cheap wide angle oculars behave like champs from the centre to the edge of the field and this means that one does not need to splash out relatively large sums of money for well corrected deep sky views using heavy 2-inch oculars. The maximum true field that can be achieved with this refractor from my eyepiece arsenal is 1.79 angular degrees, power 38x. In contrast, the much faster f/5 optical system in the Newtonian requires better eyepieces that can correct for the significant off axis aberrations including coma, astigmatism and field curvature etc. But it is able to deliver a considerably larger true field than the refractor (2.3 degrees with a Celestron X-Cel LX 25mm and 2.5 degrees with a standard 32mm Plossl, though with inferior correction towards the edge of the field).

The closest match I could make to the 38x of the refractor was to couple a 1.6x Barlow to the Celestron X-Cel LX 25mm yielding a 1.44 degree true field and a power of 42x.

Low power, wide-field oculars used in the tests; a 40mm ES Maxvision and a 25mm Celestron X-Cel LX coupled to a 1.6x Barlow. The oculars yield 38x and 42x in the 5″ f/12 glass and 130mm f/5 Newtonian, respectively.

 

For higher power, deep sky comparisons, I employed a 11mm ES 82 ocular in the f/12 refractor and a 4.8mm T1 Nagler (also 82 degree AFOV) in the 130mm reflector, delivering very comparable powers of 139x and 135x, respectively.

The 4.8mm T1 Televue Nagler ( left) and the 11mm Explore Scientific 82 degree ocular delivering 135x and 139x in the Newtonian and refractor, respectively.

 

Results: Just two targets were examined: M13 in Hercules and The Double Cluster in Perseus. In the low power setting, the refractor offered a slightly punchier image of M13, with slightly greater contrast (darker sky background) than the reflector. The faintest stars in the field were just a tad easier to discern in the big glass than in the Newtonian, but otherwise they were very comparable. At high powers, the results were broadly the same; with the nod going to the refractor, but I was very impressed at how well the little reflector did. If I were to quantify the difference I’d estimate that the 5″ f/12 delivered maybe a 5 to 10% improvement over the reflector on this remote target.

Turning next to the Double Cluster, I returned to lower power. Going back and forth between the images, the views were more comparable than they were different. Contrast was a little better in the refractor, with beautiful pinpoint stars strewn all across the field. The reflector gave almost the same results, with slightly less contrast and colour saturation. The refractor did however pull significantly further ahead at the edge of the field with tighter, better corrected stars, quite in keeping with its f/12 native focal ratio.

Conclusions: This series of tests, comparing two very different instruments of broadly similar aperture is almost never done by amateur astronomers. Doubtless, part of the reason for this is that no one wants to be told that a very expensive refractor could be rivalled by a far less expensive reflector on the same targets. And yet, apart from the clear superiority of the reflector during daylight use, this is very much the conclusion I was forced to draw; the views are very comparable. I believe the results are attributed to the superior coatings on the mirrors which collect very similar amounts of light as well as the relatively small central obstruction in the reflector which tends to keep image contrast high. Had the Newtonian possessed standard coatings, I believe I would have reported a larger difference in their performance on deep sky objects. This, together with very close attention to attaining perfect collimation in the Newtonian readily explains why it performed so well  in comparison with the refractor on high resolution point sources, such as double and multiple stars. At the very high powers employed in test 2, the coma free field is much reduced in the reflector, allowing good images to be maintained from the centre of the field to its periphery.

But in all such comparisons, it pays to also consider the comfort factor; that is, how easy the instruments are to transport, mount and manoeuvre in field use. This is where the Newtonian rocks in comparison to the refractor. It is quite simply a joy to use; no hunching behind an eyepiece very low to the ground, no need to re-balance the telescope when it’s pointed to targets of greatly different altitude etc. The small advantages the refractor has over the reflector pale into insignificance when these considerations are accommodated.

Newtonians have clearly come a long way; with modern high reflectivity coatings, quality primary and secondary mirrors and careful attention to collimation and cooling, they compete very favourably with refractors, at a fraction of the cost. I hope you can appreciate why I almost always reach for the little 130mm reflector in comparsion to the refractor. Granted, the latter may look more majestic in the cold light of day, but all this is quickly forgotten under a clear, dark country sky.

 

 

Neil English explores four centuries of telescopic astronomy in his ambitious new work (772 pages), Chronicling the Golden Age of Astronomy, due out in October 2018.

 

 

De Fideli.

An Observing Report from the English Lake District.

Plotina: a 130mm f/5 Newtonian that just goes on debunking myths promulgated by armchair astronomers, poodle pushers and fake theorists.

 

August 15 2018

                                           

Preamble: No doubt you’ve heard one or more of these statements before;

” My skies are never good enough to get steady views”

” The bleedin’ jetstream always gets the better of me.”

“The British Isles suck when it comes to doing visual astronomy.”

” Climate change is making our skies more cloudy, making small refractors more profitable to use.”

” It’s been cloudy for weeks and months on end.”

” My refractor cuts through the seeing like nothing else!”

What do they all have in common?

Lies, more damn lies, or gross distortions of the truth!

You see, I’ve been doing my homework, testing out a modest 130mm f/5 Newtonian reflector all over the British Isles, and finding that many places are plenty good enough for doing high-resolution planetary, lunar and double star observing. And from dark places, low-power, deep sky observing is also very much worthwhile.

Don’t believe me?

Do I sound like I care?

Stick this in your proverbial pipe and smoke it: if only you got off your big, fat, wicked, lazy butt and did some real testing you’d soon come to a knowledge of the truth!

Moi? I’ve observed with the same telescope from no less than five counties in Southern Ireland, the windswept Isle of Skye in Northwest Scotland, Aviemore in the heart of the Scottish Highlands, and rural Aberdeenshire in Northeast Scotland, Wigtown in Southwest Scotland, Seahouses in Northeast England and even in the heart of the large cities of Glasgow and Edinburgh. Most recently, I tested a site in southern Lakeland, Cumbria, the subject of the present observing report.

Thus far this year, I have logged 78 separate sessions under the stars (not all perfectly clear and not all long sessions), either at home here in my rural site just north of the Scottish Central Belt, or while on holiday, and no doubt there were still more nights when I was unable to observe or it cleared too late or some such to conduct any more observations. That’s 78 out of 226 nights, or just shy of 35 per cent! So, more frequently than one in every three nights proved profitable. But I suspect the figure is nearer 40 per cent.

How do these data resonate with the above statements?

They don’t, do they?

Get yer logbooks oot……lemme see yer logbooks.

 

Sheer dumb luck?

Don’t give me that either!

I don’t believe in sheer dumb luck. Nor do I spend my precious time haunting telescope forums, you know, drooling over this instrument or that.

Nope; I’m an observer!

So I just go observing lol. You know, actually looking through my telescope; it’s not so hard is it?

Anyone with a deep enough interest in such things would quickly draw the same conclusions, at least on the British Isles.

Do I believe these findings are unique to Britannia et Hibernia?

Hell no!

Why should they be?

Surely, most of these observations were conducted during warmer, more settled spells, like in Summer?

Nope, computer says no! Check my logbooks!

Good spells occur in all weathers, from freezing cold nights to sweltering hot ones!

Have these data any historical precedents?

Absolutely yes!

See my up-and-coming book, Chronicling the Golden Age of Astronomy, for a full disclosure.

If you take the time to examine the frequency of key historical figures who loved the night sky, you’d find fairly similar results in the literature.

How do I know?

I’ve studied those historical cases.

Phew! Quite a rant there!

But better a rebuke than faint praise eh?

Now, shall we get down to business?

 

Introduction:

Plotina; the author’s ultra-portable 130mm f/5 Newtonian sampling the skies from the southern Lake District, Cumbria, England.

 

A 5.1″ f/5 Newtonian was transported in its custom aluminium case to a site in Southern Lakeland, Cumbria (Latitude: 54.5 degrees North) to establish whether conditions were good enough to resolve a number of test double stars and to more generally assess the seeing and transparency at this location. The success of this modest ultra-portable instrument at various sites within the UK and Ireland has been truly remarkable, so much so that this author has totally abandoned more traditional instruments such as Maksutovs and refractors in favour of this small Newtonian to pursue all areas of grab ‘n’ go amateur astronomy. As explained in a number of previous blogs, the telescope sports a significantly greater aperture (130mm) than your run-of-the-mill grab ‘n’ go telescopes. Possessing a high quality optical flat resulting in a modest 27 per cent (linear) central obstruction, it is significantly smaller than all commercial catadioptrics and sports very high reflectivity coatings that produce bright, crisp images, very comparable to an equivalent sized refracting telescope. In addition, its relatively low mass and open-tubed optics ensures that it cools more rapidly than a similar-sized refractor or catadioptric.

During the trip, just one evening turned out clear, namely the night of Friday, August 10-11 2018.

Conditions:

Mostly clear with some patchy cloud. Temperatures were cool (12C), with a brisk south-westerly breeze, which continued to gust for several hours, abating almost entirely by local midnight. Transparency proved very good and although there was some light pollution owing to neighboring mobile homes, the sky was good and dark. Indeed, I judged the site a little darker than at my rural observing site in Scotland, with the northern Milky Way seen more prominently, snaking its way from northeast to southwest. The northern and eastern sky was especially dark, prominently revealing the majestic constellations of Cassiopeia, Andromeda, Pegasus, while high overhead lay Cygnus and Lyra. The site had a good view of the southern sky, with Aquila and Delphinus situated very close to the meridian. Two bright planets graced the southern sky low down, a dull yellow Saturn and further east, brilliant red Mars.

Method:

The telescope was precisely collimated using a good quality Chesire eyepiece and left to cool for about 20 minutes, with the open tube pointing straight into the prevailing (south-westerly) winds at the site. A working magnification of 260x was adopted to examine a number of test double stars. This was achieved by coupling a 7.5mm Parks Gold eyepiece and Meade 3x achromatic Barlow lens.

For widefield sweeping, a 25mm Celestron X-Cel LX  was used, deliverng a power of 26x in a  2.3 degree true field. Higher power deep sky views were enjoyed with a 5.5mm Meade ultra-wide angle ocular which yields a power of 118x in a 0.7 degree true field. Mars and Saturn were observed at a power of 177x (using an 11mm eyepiece and 3x Barlow), which proved more than adequate, as both orbs were situated very low down in the southern sky around local midnight.

The test double stars were chosen for their easy accessibility as well as being progressively more difficult;

Epsilon 1 & 2 Lyrae

Epsiion Bootis

Delta Cygni

Mu Cygni

Pi Aquilae

Lambda Cygni (examined at 354x using a 5.5mm eyepiece coupled to a 3x achromatic Barlow).

Double Star Results:

The first five test systems produced text-book perfect splits at 260x, the components being very cleanly resolved, and the individual stars presenting as perfectly round Airy disks with a single but rather subdued diffraction ring. The sub-arcsecond pair, Lambda Cygni, revealed its near-equal magnitude components as ‘kissing’ at 354x. You can’t do that with a 4-inch refractor; see here for just one example.

Additionally, the wonderful triple star system, Iota Cassiopeia, was examined later in the vigil, when the constellation had risen higher in the northeastern sky. I was rewarded with a perfectly resolved rendering of all three components at 260x using the 130mm f/5 Newtonian.

Conclusions: 

Despite enjoying just one clear night at this site during our short vacation, I achieved what I have come to view as fairly typical results for many locations in the British Isles. The telescope was able to deliver excellent high-resolution results on these test double stars. As stated earlier, I do not especially attribute these results to serendipity. Indeed, I have come to expect such results when conditions are reasonable at many sites within the UK and Ireland. Such results can easily be achieved by other observers using the same (read modest) equipment with just a little attention to detail; adequate acclimation and close attention to accurate collimation, which can be executed perfectly in under a minute. I would encourage others to test these claims so that these results become as widely known as possible.

Newtonian telescopes will continue to be my instruments of choice to observe such systems in the future, so as to help dispel a particualrly virulent myth that has arisen within the amateur community; a myth born out of ignorance and old fashioned laziness. Such a myth is plainly false and will allow many more observers to pursue such targets with unpretentious instruments that are very reasonably priced.

Observing the Planets:

Although certainly not a dedicated planetary observer, I have come to appreciate the very good views of Jupiter in recent apparitions using the 130mm f/5 Newtonian. During this vigil, my family and I enjoyed very nice, crisp images of Saturn with the telescope at 177x. Despite its low altitude in the southern sky, the planet revealed its glorious white rings with the Cassini Division being plainly seen. Some atmopsheric banding was also observed but, being much farther away, these features are much more subdued than on mighty Jupiter.

Mars was examined at the same power. This was actually the very first time the planet was observed telescopically during the present apparition. The view served up by the telescope was shockingly good and to be honest, not at all anticipated owing to its even lower altitude near the southern horizon. First off, I was amazed at how large the planet looked at 177x (a rather low power for a 5.1″ telescope on such a target generally). Though the image was roiling in the perturbed atmosphere near the local horizon, I was able to make out some dark markings on the planet as well as a rather subdued southern polar ice cap. I was aware that the planet had recently experienced a planet-wide dust storm that all but occluded many of the surface features but I was pleased to see that, while much dust was still present in the atmosphere, it was clearly settling out at the time the observations were made. Mars was a big hit with the family; its large size and great brightness to the naked eye being a lively topic of conversation with my wife and sons.

Into the Deep Sky:

Plotina is a step above the rest of the grab ‘n’ go herd with regard to deep sky observing. It’s highly efficient 5.1″ primary mirror collects enough light to put it in a different league to 90 and 100mm refractors.

How do I know?

I’ve done extensive tests with a 90mm Apo (shown below) and my notes show that double stars hard to see with a four inch refractor are easier to see and resolve in the 130mm reflector. It’s not rocket science!

Faster, cheaper, better: The author’s 130mm f/5 modified Newtonian( Plotina) enjoying crisp, bright terrestrial views and in a completely different league to a 90mm f/5.5 ED apochromat(left).

With the glorious return of true darkness to northern British skies, my first port of call was the endlessly glorious Double Cluster in Perseus. This is where the 25mm Celestron X-Cel LX eyepiece really shone through for me. I don’t know if you’ve ever held on to an eyepiece because of how well it frames a deep sky object, but this ocular delivered an absolutely beautiful, expansive view of the famous open clusters. It’s very comfortable 60 degree AFOV delivers a true field of 2.3 degrees at 26x, centring the clusters perfectly in the middle of the field and showing just enough of the rich stellar hinterland to render the experience particularly memorable. The perfect achromatism of the Newtonian delivers the pure colours of the white, yellow, blue and ruby coloured suns decorating these wonders of nature, each of which are located over 7,000 light years away. I stared at these clusters for a full 10 minutes before dragging my eyeball away!

Next, I pointed the telescope into the heart of Cygnus and drank up the sumptious views of the northern Milky Way, moving the instrument slowly from field to field in awe of the sheer number of stars this wonderful 5.1-inch pulled in. Sometimes deep sky observing is not about seeking out any particular object; for me, it often involves just sweeping the telescope through an interesting swathe of sky, sitting back and enjoying the visual sensations that bring joy to the eye-brain.

My telescopic sojourns eventually took me into Vulpecula, where I quickly chanced upon Brocchi’s Cluster (Collinder 399), otherwise known as the Coathanger, owing to its extraordinary configuation of half a dozen stars arranged just like its common name suggests and spanning over 1.5 degrees of sky, which was easily handled by the 25mm Celestron ocular.

Skies were good and dark enough to observe a number of planetary nebulae in Vulpecula, Lyra and Hercules and for these, I switched out the 25mm ocular for the 5.5mm Meade Ultrawide angle delivering 118x in a fine 0.7 degree true field. Easy to pick up in my 6 x 30mm finder as an 8th magnitude smudge, the 5.1-inch Newtonian delivered an awesome view of M27, the famous Dumbbell Nebula, its enormous size occupying a space fully a quarter the size of the full Moon. I find such structures haunting in the telescope and a kind of shiver went down my spine as I studied its enormous bi-lobed morphology alone in the dark (the wife and kids having now retired for the night). Moving west into Hercules nextdoor, I sought a spot about 4 degrees northeast of the fairly bright star, Beta Herculis. With the generous, wide field of the 5.5mm I didn’t have to switch out for a lower power eyepiece to find the lovely 9th magnitude planetary, NGC 6210. The telescope made light work of picking up its distinctive oval shape and its soft bluish hue. Finally I ventured east again into Lyra, where the telescope made light work of picking up the endlessly interesting M57, the famous Ring Nebula, easily located smack bang in the middle between Beta and Gamma Lyrae. At 188x, this planetary looks big and bright with its inner and brighter outer structures showing up well. It’s amazing that this luminous smoke ring in the August sky is estimated to be a full light year in diameter!

Having studied the bright and comparitively huge globular clusters, M13 and M92 at home in Scotland with my 12″ f/5 Dob, I was impressed at how well they presented themselves in the little 5.1-inch lightcup at 118x. I was in for a bit of shock though when I eventually tracked down M56 in Lyra, located roughly half way between Albireo and Gamma Lyrae. In the 5.5mm eyepiece, this globular was considerably smaller and fainter, looking more like a nebula than anything else. When I cranked up the power to 177x, the view was little improved; just a bright but unresolved core with a smattering of faint stars hovering like little fireflies around it. The view in my 8-inch Dob is far better but still rather lacklustre. I find my 12-inch Dob to do proper justice to this cluster and its gorgeous hinterland of Milky Way stars.

I ended my vigil in the wee small hours of Saturday morning, August 11, with a ceremonial visit to M31 and its satellite galaxies, now riding about one third of the way up the eastern sky. To be honest, galaxies never do much for me and I don’t really understand why folk in possession of larger instruments want to look at them in very small telescopes. Some say it’s heroic and admirable to do that kind of thing but I think it’s bordering on nuts. Why struggle to observe such faint fuzzies when you can more easily study them in larger telescopes? Anyway, the decent light grasp and expansive 2.3 degree field of my new Celestron LX ocular delivered a sterling view of this showpiece object of the autumn sky.

It was good to get away; our first visit to the beautiful Lake District. But all good things have to come to an end I guess.

 

The author did not emerge from pond scum and cannot for the life of him understand why anyone else would have such a low opinion of themselves. Such are the false fruits of evolutionary ‘science.’

 

 

 

De Fideli.