A Tale of Three Binoculars

My 30-year old 7 x 50 binocular.

 

It was just over 30 years ago when I was gifted a nice 7 x 50 binocular by my girlfriend. They featured a 7 degree field, multi-coated optics and BaK-4 porro prisms. They served me well all these years on holidays, walks and for casual stargazing. They weren’t cheap either. Lesser units would have fallen apart by now, but after trying a few modern binoculars out I knew that technology had moved on, mostly for the better.

And so had my eyes.

Now that I’m older, I wanted a binocular that had an exit pupil more suited to my age. I wanted an instrument that was more light weight, so that I could observe for longer without using tripods. I wanted a binocular that would do well in a variety of situations, from nature watching from dawn to dusk, and for astronomy. They had to be robust and ideally weatherproof to a degree. My ideal binocular views had to serve up sharp, colour pure views of autumn’s radiant hues but also allow me to throw caution to the wind and just enjoy the glories of the night sky from the comfort of a recliner. But which ones to buy?

Alas, I found that choosing a model that ticked all the boxes for me to be a daunting prospect! Today, we have so many makes to choose from; which is a good thing. My experience with telescopes came in very handy though. Not easily swayed by marketing gimmicks and wishy-washy hyperbole, I slowly pared them down to size.

I decided I wanted a fairly compact, full-size binocular that would offer good light grasp, so a clear aperture of 42mm would be about the minimum that would do the trick. I wanted a fully multi-coated instrument to maximise light transmission to the eye and reduce glare on bright objects to an acceptable minimum. They had to be well made with a decent warranty should they get damaged or worn out from regular use. And they had to present good value for my hard-earned cash.

I narrowed my search down to a good roof-prism binocular as these had many of the features I was looking for; small, light weight, decent light grasp, ultraportable etc. Two magnifications were considered, 8x or 10x. With 10x you’d get a smaller exit pupil and lose some advantages of using them in low light conditions. 10x would also introduce more shake and would be more difficult to accurately focus while in use too, so I decided on 8x; an 8 x 42 binocular.

I went to amazon.co.uk to check out the user reviews of a variety of models I had an interest in. In many ways, these types of reviews give the prospective buyer a more rounded view of what it’s like to use a given model, as they are often more honest and less biased than those offered by so-called ‘experts,’ who, more often than not, succumb to clever marketing ploys and had a tendency to push premium products over more economical models that might still offer perfectly acceptable performance. I found that birders, for example, often highlighted a variety of mechanical and optical features that were largerly superfluous to my needs. I didn’t really need super-fast focusing, locked in dioptre settings, nor ED elements in the objectives. At such low powers, one would be hard pressed to see the advantages of employing low dispersion glass and most of the online literature seemed to over-emphasise their advantages even though I knew that it would only make a small (insignificant?) difference to the views. Afterall, how many amateur astronomers insist on having ED finder ‘scopes eh? Why haven’t 8 x 50 ED finders or some such become the industry standard, if they really offered any tangible advantage over good ole crown & flint? The honest answer is that they’re unnecessary, and so can be dispensed with.

As a case in point, check out this user review of the Vortex 10 x 42 Diamondback roof prism binocular. The gentleman states that he was asked to try out the more expensive Viper model with ED objective elements in a blind test. He states that he couldn’t really tell the difference in field use. I have no reason to doubt the gentleman’s conviction. Why lie on such a trivial matter?

No, a good, no-frills, traditional achromatic binocular to match my average eyes was what I was shopping for!

I went with a company that had a long track record of producing high quality optics, as I reasoned that such knowledge would be invaluable in the construction of a well-made binocular. Many companies selling such binoculars were not long in the game though, so my instinct was to avoid them. I gravitated toward an old British firm that had produced optics for the military in two world wars; Barr & Stroud.

Now bought out by OVL, Barr & Stroud  re-entered the sports optics market by bringing out a range of affordable roof prism binoculars in an 8 x 42 format and my first purchase was the Sahara 8 x 42, which retails for about £70-£90 UK.

The Barr & Stroud Sahara 8 x 42.

 

Though under no illusions that these are British made, Barr & Stroud binoculars are now assembled in China, just like those marketed by Vortex (a US-based company) and many other companies. They are supplied with a nice, soft carry case, neck straps, a lens cleaning cloth and have a 10-year warranty.

The Sahara 8 x 42 binocular comes in attractive box with a good carrying case with the usual accessories.

 

The specifications of the Sahara 8 x 42 model can be viewed here.

The Sahara is a joy to use. It’s small and light weight (670g), has good eye relief (17.5 mm) and with its twist up eyecups, will allow those who must wear eye glasses (I don’t) to enjoy the expansive field of view (7.33 angular degrees). Images are bright and sharp and colour fidelity is sound. With its fully multi-coated optics, contrast and glare suppression are excellent too in comparison to my old 7 x 50s. You really have to look for chromatic aberration but it is there. You can best see it by focusing on the edge of a telephone pole against a bright, overcast sky background, but is minimal and not in the least bit intrusive(I’d say mostly bum-fluff). At the edge of the field, the image gets a little softer with some slight fringing during daylight hours but it will never be enough to disturb the vast majority of users. Focusing is smooth and intuitive, not overly stiff or loose and it has an excellent close focus distance of just under 2m (measured) to allow you to enjoy insects, flowers etc at close range. It also has adequate waterproofing for my intended uses for it.

Night time views were very impressive too. Stars are sharp and pinpoint across the majority of the field. Only by using a stable tripod, will you be able to notice a little defocus of the stellar images at the edge of the field. All in, I would rate the Sahara as very good and considering its modest cost; a great bargain in today’s market! These guys certainly know how to make a good binocular!

Shortly after purchasing the Saharas, I began researching the properties of roof prisms and discovered that they have a significant design flaw. In the roof prism design, the two halves of the collected light from the objectives travel through the prism independently and are recombined before reaching the eyepieces. Because the path of the two wave trains are of slightly different lengths, one half of the light takes a little longer to travel through the prism than the other. When the two halves of the image are recombined, the wave with the longer light path will be slightly out of phase with the light that undergoes the shorter route. This results in a combination of destructive and constructive interference of the wave trains, affecting the colour balance, contrast and fidelity of the binocular image.

Note that this flaw does not affect porro-prism-based binoculars!

By introducing a special phase coating to the prism undergoing the shorter light path, optical designers can slightly retard the wave train, thereby correcting the phase difference with the other wave train. This results in sharper, brighter images with higher contrast; in theory. As I researched this some more, I discovered that the result was quantitatively significant; 8 per cent according to the manufacturers. Intrigued, I looked for a Barr & Stroud model that had this phase coating as the Sahara’s did not have this technology built in and that quickly led me to their 8 x 42 Sierra model.

The Barr & Stroud 8 x 42 Sierra binocular.

 

Luckily, the Sierra was only a little bit more expensive than the Sahara. Full specs here.

Otherwise sharing very similar specifications to the Sahara, the Sierra 8 x 42 is also slightly lighter (650g), coming with the same soft carry case and accessories as the former. The polycarbonate body was also a little different in the Sierra compared with the Sahara, as the above images show. When it arrived, the first thing I did was undergo a test to see if there was any significant difference between the images. Examining a brightly lit scene with a trunk of a tree shadowed by some over-hanging branches and comparing the two binocular images, I must admit that the Sierra was that little bit better. It’s difficult to describe in words but I suppose I’d say that the Sierra image had a little bit more ‘zing’ to it. The image was that little bit brighter and the colours more vivid. Contrast was also better by a shade.

Based on this test, I think phase coating technology is definitely worth having. Subsequent research of other high-end and mid-priced binoculars revealed that they all possessed these phase coatings. I see them as increasing the overall efficiency of light transmission, improving the image in a way that the human eye would notice in a critical test.

In another test comparing my 7 x 50s to the Sierra’s, I had to immediately concede that the images in the latter were far superior to the old porro prism binocular. The image was actually brighter even though it only had 42mm objectives(as opposed to 50mm in the auld yin) and the contrast far superior. The Sierra also presented a larger field of view.

Man and his technology!

Before describing my experiences with the Sierra 8 x 42 in any more detail, I was curious to see how the unit would fare compared with a high-end binocular with roughly the same specifications. As luck would have it, my coalman is a keen birder and dabbles in hunting big game. He’s the proud possessor of a Swarovksi EL 8.5 x 42 binocular, which retails for about £1800 UK. When he came to deliver some coal I got chatting with him and asked him if he would be so kind as to bring them by some afternoon so that we could compare and contrast the images garnered by these binoculars. He agreed.

The Swarovski EL 8.5 x 42 roof prism binocular.

 

Though certainly not a ‘gayponaut’ (a word of my own coining, fomally defined as: an irrational obsession with small ED optics), my coalman, Graham, bought his Swarovski’s about ten years ago, and I was glad to see that they looked as though they’d been used. When I asked him why he chose them he said, “they’re supposed to give brighter views in low light.”  I thought that answer was a little vague though. He didn’t seem to know anything about the fluorite element in the objectives, or the effects of coatings on the optics. He was simply won over by the advertising. I believe this is common among buyers of high-end optics. Afterall, you don’t need to know anything about an internal combustion engine in order to drive a car do you?

Indeed, I knew far more about his Swarovski’s than he did. Nevertheless, we compared the images. I got a shot of Graham’s 8.5 x 42s and he got a chance to test out my 8 x 42 Sierra’s. The results were interesting.

I felt the image quality was excellent in the Swarovski’s. It gave a slightly more neutral colour tone to the Sierra’s in a very slightly larger true field (7.6 angular degrees). Contrast was excellent with really first-rate definition. The built-in field flattening lenses in the eyepieces improved the edge of field correction, and the slight colour fringing I had tried hard to detect in my Sierras was invisible in the Swarovski’s.

Graham liked the Sierras too though. Indeed, he said to me that, ” they’re pretty much the same aren’t they?”

I found it hard not to disagree. I felt the images were much more similar than different.

But what I did appreciate were the mechanical attributes of Graham’s binocular. Its buttery smooth focusing wheel made it easy to adjust focus distance from about 4.5 feet to infinity very swiftly; a bonus for birders I guess. I also appreciated the wonderful diopter adjustment apparatus and hearing the ‘click’ as it was turned to the correct setting.  This clever diopter locking mechanism means that there’s little chance of it slipping out of place during field use. Great, but not something I couldn’t live without.

The Swarovski’s body is a very rugged magnesium alloy chassis which gives a feeling of reassurance while handling the optic, but I didn’t really understand how it would be more resistant to corrosion over the far less expensive polycarbonate body usually found on the majority of sports optics. What Graham and I did notice was the significant weight difference between the models. The Swarovski’s were nearly 200g heavier than the Sierra’s, something that would definitely have a bearing on observing comfort during prolonged field use.

The excellent life-time warranty on the Swarovski’s was something Graham appreciated. He told me that one of the caps on the ocular lens had worn out (they can actually be removed for easy cleaning of the eye lenses) but one of the company reps immediately fitted his unit with a new one; that’s great service!

In the end, I was very grateful to Graham for bringing by his high-end binocular. I was delighted to know that there wasn’t much in it optically. But then again, I kind of expected as much! Did the experience tempt me to save and invest in a Swarovski? I’d have to say no. My Sierra’s were plenty good enough, warts and all!

What to do with the Sahara’s? My sister- and brother-in-law love the great outdoors; camping, glamping, fly fishing, hill walking and sight seeing. The’ve never owned a decent binocular so these will serve as a suitable Christmas gift for them. I just know they’ll love it and use it!

As for the Barr & Stroud Sierra binocular, I will present a separate, in depth review of this instrument in another blog.

Thanks for reading!

 

Neil English is author of several books on amateur astronomy.

 

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.

Investigating the Jet Stream

but test everything; hold fast what is good.

                                                                           1 Thessalonians 5:21

 

My Local Weather

 

Jet Stream Data

Introduction:  One of the statements that is oft quoted by observers, particularly in the UK, is that the meteorological phenomenon known as the Jet Stream seriously affects the quality of high resolution telescopic targets. I have decided to investigate these claims to determine to what extent they are true or not, as the case may be. These data will also provide the reader with an idea of the frequency of nights that are available for this kind of testing over the time period the study is to be conducted.

Method: For simplicity, I shall confine my studies to just four double stars that have long been considered reasonably tricky targets for telescopists. To begin with, my targets will include systems of varying difficulty, ranging from 2.5″ to 1.5″ separation, and the aim is to establish whether or not I can resolve the components at high magnification. These systems include *:

Epsilon 1 & 2 Lyrae

Epsilon Bootis

Delta Cygni

Pi Aquilae

* These systems were chosen for their easy location in my current skies, but may be subject to change as the season(s) progress.

Viewers are warmy welcomed to conduct their own set of observations to compare and contrast results in due course.

Instrument Choice & Magnifications Employed:

The 130mm f/5 Newtonian telescope used in the present investigation.

 

A high-performance 130mm (5.1″) f/5 Newtonian reflector was employed to investigate the effects of this phenomenon, as this is an aperture regularly quoted as being sensitive to the vagaries of the atmosphere. Magnifications employed were 260x or 354x (they can however be resolved with less power). The instrument at all times was adequately acclimated to ambient temperatures and care was taken to ensure good collimation of the optical train. No cooling fans used on any of my instruments.

Results;

Date: August 17 2018

Time: 21:20 to 21:35 UT

Location of Jet Stream: Currently over Scotland

Conditions: Mild, 14C, very breezy, mostly cloudy with occasional clear spells, frequent light drizzle.

Observations: Power employed at the telescope 354x

Epsilon 1 & 2 Lyrae: all four components cleanly resolved.

Delta Cygni: Faint companion clearly observed during calmer moments

Epsilon Bootis: Both components clearly resolved during calmer moments.

Pi Aquilae: Slightly mushier view, but both components resolved momentarily during calmer spells.

Truth seeking.

 

Date: August 19 2018

Time: 20:30 – 21:50 UT

Location of Jet Stream: Currently over Scotland.

Conditions: Mild, 13C, mostly cloudy and damp all day but a clear spell occurred during the times stated above, no wind, heavy dew at end of vigil.

Observations: Seeing excellent this evening (Antoniadi I-II); textbook perfect images of all four test systems at 354x and 260x.

Nota bene: A 12″ f/5 Newtonian was also fielded to test collimation techniques and I was greeted with a magnificent split of Lambda Cygni (0.94″) at 663X. Little in the way of turbulence experienced even at these ultra-high powers. Did not test this system on the 130mm f/5.

Clouded up again shortly before 11pm local time, when the vigil was ended.

Date: August 22 2018

Time: 23:30-40 UT

Location of Jet Stream: Currently over Scotland

Conditions: Very mild (15C), breezy, predominantly cloudy with some heavy rain showers interspersed by some brief, patchy clearings.

Observations: Just two test systems examined tonight owing to extremely limited accessibility; Epsilon 1 & 2 Lyrae and Delta Cygni. Both resolved well at 260x.

 

Date: August 22 2018

Time: 21:00-21:25UT

Location of Jet Stream: Currently over Scotland

Conditions; partially cloudy, brisk southwesterly wind, bright Gibbous Moon culminating in the south, +10C, rather cool, transparency poor away from zenith.

Observations: The telescope was uncapped and aimed straight into the prevailing SW wind, as is my custom.

All four systems well resolved at 354x, although visibility of Pi Aql was poor owing to thin cloud covering.

 

Date: August 23 2018

Time: 20:30-45 UT

Location of Jet Stream: Moved well south of Scotland

Conditions: Mostly clear this evening, after enduring heavy showers all day; cool, 10C, fresh westerly breeze, good transparency.

Observations:  All four test systems beautifully resolved this evening (seeing Ant II) at 354x. Just slightly more turbulent than the excellent night of August 19 last.

 

Date: August 24 2018

Time: 20:30-45 UT

Location of Jet Stream: Just west of my observing site.

Conditions: Almost a carbon copy of last night, light westerly winds, cool (9C), good transparency and almost no cloud cover. Very low full Moon in south-southeast.

Observations: All four system resolved at 260x, but less well at 354x owing to slightly deteriorated seeing ( II-III). Delta Cygni seems especially sensitive to seeing.

Nota bene: Epsilon Bootis now sinking fast into the western sky. This test system will soon be replaced by a tougher target, located higher up in my skies; Mu Cygni.

A capital telescope.

 

Date: August 25 2018

Time: 20:20-21:00 UT

Location of Jet Stream: Right over Scotland.

Conditions: Very hazy, calm, poor transparency, cool (9C), seeing excellent (I-II)

Observations: Just three of the four systems examined tonight owing to very poor transparency. Only Pi Aquilae could not be examined. All three were beautifully resolved at 354x.

 

Date: August 26 2018

Time: 22:30-23:05 UT

Location of Jet Stream: Well south of Scotland.

Conditions: After a day of heavy rain, the skies cleared partially around 11pm local time. Fresh westerly breeze, fairly mild (12C), bright full Moon low in the south.

Observations: Mu Cygni observed instead of Epsilon Bootis owing to the latter’s sinking low into the western sky at the rather late time the observations were made.

Three systems well resolved ( Mu Cygni, Pi Aquliae and Epsilon 1 & 2 Lyrae) in only fair seeing, with Delta Cygni B only spotted sporadically in moments of better seeing. This system is very sensitive to atmospheric turbulence due to a large magnitude difference between components, as opposed to their angular separation. 260x used throughout.

Nota bene: Readers will take note of the frequency of observations thus far made.

Date: August 27 2018

Time: 20:30-21:05 UT

Location of Jet Stream: West of the Scottish mainland.

Conditions: Mostly cloudy, mild, 13C, light westerly breeze.

Observations: I took advantage of a few brief clear spells this evening to target my systems(including Epsilon Bootis). Seeing very good despite the cloud cover (II). All four systems easily resolved tonight at both 354x and 260x.

Date: August 29 2018

Time: 20:25-40UT

Location of Jet Stream: Not over Scotland.

Conditions: Mostly clear, occasional light shower, cool (11C), light westerly breeze, seeing and transparencyvery good (II).

Observations: Mu Cygni now replaces Epsilon Bootis.

All systems very cleanly resolved at 354x and 260x.

Nb. All systems also beautifully resolved in a 12″ f/5 Newtonian at 277x, set up alongside the 130mm f/5.

 

Date: August 30 2018

Time: 20:45- 21:00 UT

Location of the Jet Stream:  Not over Scotland.

Conditions: Partially cloudy with some good clear spells, cool (9C), very little breeze.

Observations: Seeing good tonight (II). All  four systems nicely resolved at 260x and 354x.

Note added in proof: Local seeing deteriorated (III-IV) somewhat between 21:00 and 22:00 UT, so much so that Delta Cygni B could no longer be seen.

 

Date: 31 August 2018

Time: 20:30-22:00UT

Location of Jet Stream: North of the British Isles

Conditions: Partly cloudy and becoming progressively more hazy as the vigil progressed. Mild, 12C, very light westerly breeze.

Observations: Seeing only fair this evning (II-III), all four systems resolved at 260x and 354x, though Delta Cygni B visibility was variable.

 

Date: September 1 2018

Time: 20:30-50UT

Location of Jet Stream: to the northwest of the Scottish Mainland.

Conditions: Partially clear, very mild (16C), light southerly breeze, good transparency.

Observations: Seeing quite good (II).  All four systems resolved at 260x and even better delineated at 354x under these clement conditions.

 

Date: September 4 2018

Time: 19:55-20:20UT

Location of Jet Stream: Not over Scotland.

Conditions: Cool (10C), mostly clear, light westerly breeze, good transparency.

Observations: Seeing very good (II).  All four test systems well resolved at 260x and 354x this evening.

 

Date: September 5 2018

Time: 20:35-20:55UT

Location of Jet Stream: Not over Scotland.

Conditions: Very unsettled with frequent squally rain showers driven in by fresh westerly winds. Good clear spells appearing between showers. Transparency very good. 12C

Observations: All four test systems resolved under good seeing conditions (II) at 260x and 354x.

 

Date: September 6 2018

Time: 20:00-25 UT

Location of Jet Stream: Not over Scotland.

Conditions: Cool (8C), little in the way of a breeze, mostly clear, excellent transparency.

Observations: Seeing good (II). All four test systems well resolved at 260x and 354x.

 

Date: September 7 2018

Time: 20:25-40UT

Location of Jet Stream: Not over Scotland.

Conditions: A capital evening in the glen; 11C, good clear sky, brisk westerly breeze, excellent transparency.

Observations: Seeing very good (I-II).  All four test systems beautifully resolved in the 130mm f/5 using powers of 260x and 354x

Nota bene:

Know thine history!

Any serious student of the history of astronomy will likely be acquainted with the early work of Sir William Herschel (Bath, southwest England), who employed extremely high powers (up to 2000x usually but actually he went as high as 6,000x on occasion) productively in his fine 6.3-inch Newtonian reflector with its speculum metal mirrors. The high powers employed by this author are thus fairly modest in comparison to those used by his great predecessor. Check out the author’s new book; Chronicling the Golden Age of Astronomy, due out in October/November 2018, for more details.

Note added in proof:

With the excellent conditions maintained well after midnight, I ventured out at about 00:00 UT,  September 8, and noted Andromeda had attained a decent altitude in the eastern sky. At 00:10UT I trained the 130mm f/5 Newtonian on 36 Andromedae for the first time this season and charged the instrument with a power of 406x. Carefully focusing, I was treated to a textbook-perfect split of the 6th magnitude Dawes classic pair that are ~1.0″ apart. It was very easy on this clement  night. The pair look decidely yellow in the little Newtonian reflector. I made a sketch of their orientation relative to the drift of the field; shown below.

36 Andromedae as seen in the wee small hours of September 8 2018 through the author’s 130mm f/5 Newtonian reflector, power 406x.

 

If you have a well collimated 130P kicking about why not give this system a try over the coming weeks?

 

Date: September 9 2018

Time: 21:10-25UT

Location of Jet Stream: Currently over Scotland

Conditions: Frequent heavy showers driven in from the Atlantic with strong gusts, 11C, some intermittent clear spells.

Observations: Seeing III. 3 systems fairly well resolved this evening. Delta Cygni B only seen intermittently. Magnification held at 260x owing to blustery conditions.

Date: September 12 2018

Time: 00:10-20UT

Location of Jet Stream: Currently over Scotland

Conditions: Very wet, windy with some sporadic clear spells, good transparency once the clouds move out of the way. 10C.

Observations: Seeing (II-III). Just three systems examined tonight; the exception being Pi Aquliae, which was not in a suitable position to observe. All three were well resolved at 260x. Did not attempt 354x owing to prevailing blustery conditions.

 

Date: September 12 2018

Time: 21:40-55 UT

Location of Jet Stream: Not over Scotland

Conditions: Still unsettled, blustery light drizzle and mostly cloudy with some clear spells. 10C.

Observations: Seeing (III), three systems resolved well, Delta Cygni B not seen cleanly at 260x under these conditions.

 

Date: September 14 2018

Time: 19:30-50UT

Location of Jet Stream: Currently over Scotland.

Conditions: Rather cool, (9C), very little breeze, rain cleared to give a calm, clear sky.

Observations: Seeing II. All four systems cleanly resolved at 260x and 354x

 

Date: September 16 2018

Time: 19:20-40UT

Location of Jet Stream: Currently over Scotland

Conditions: Mild (12C), fresh south-westerly breeze, some occasional clear spells.

Observations: Seeing very good (II), all four systems cleanly resolved at 260x and 354x.

 

Overall Results & Conclusions:

This study was conducted over the course of one month, from mid-August to mid-September 2018, a period covering 31 days.

The number of days where observations could be conducted was 21, or ~68% of the available nights.

No link was found between the presence of the Jet Stream and the inability to resolve four double star systems with angular separations ranging from ~2.5-1.5″. Indeed, many good nights of seeing were reported whilst the Jet Stream was over my observing location. In contrast, some of the worst conditions of seeing occurred on evenings when the Jet Stream was not situated over my observing site.

There is, however, a very strong correlation between the number of nights available for these observations and the efforts of the observer.

Many of the nights the Jet Stream was located over my observing site were windy, but this was not found to affect seeing. While the wind certainly makes observations more challenging, it is not an indicator of astronomical seeing per se. That said, no east or northeast airflows were experienced during the spell these observations were conducted. At my observing site, such airflows often bring poor seeing.

The archived data (from January 16 2014) on the Jet Sream site linked to above provide many more data points which affirm the above conclusions.

I have no reason to believe that my site is especially favoured to conduct such observations. What occurred here must be generally true at many other locations.

These results are wholly consistent with the available archives from keen observers observing from the UK in the historical past. This author knows of at least two (or possibly three) historically significant visual observers who enjoyed and documented a very high frequency of suitable observing evenings in the UK.

Contemporary observers are best advised to take Jet Stream data with a pinch of salt. It ought not deter a determined individual to carry out astronomical obervations. Perpetuating such myths does the hobby no good.

 

 

Neil English debunks many more observing myths using historical data in his new book, Chronicling the Golden Age of Astronomy, due out in October 2018.

 

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 horsechestnut 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 my my next-door neighbour, Trevor. 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.

Trevor points to the telescope offering the superior daylight images.

 

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.

Living without Lasers

Collimation tools; from left right: a SkyWatcher Next Generation laser collimator, a collimation cap, a well made Cheshire eyepiece and a Baader lasercolli Mark III.

 

It is undoubtedly true that by far the most prevalent reason why so many amateurs have dissed Newtonian reflectors in the past boils down to poorly collimated ‘scopes which lead to less than inspiring images. The amateur who pays close attention to accurate collimation will however discover the solid virtues of these marvellous telescopes and will soon forget the bad experiences of the past.

I’ve noticed a trend over the last few decades, where more and more amateurs have become lazy and impatient. They want instant gratification. This is one of the main reasons why many have turned to hassle-free instruments such as small refractors and Maksutov Cassegrains. It’s an entirely understandable trend, but in other ways it is lamentable. One of the downsides of this trend is that amateurs have become less concerned with learning practical optics, deferring instead to higher tech ways of obtaining optimal results in the field. One such technology is the laser collimator; a very useful device that has made accurate collimation far less of a chore than it was just a few decades ago. But while many have defaulted to using such tools as labour-saving devices, they have, at best, become less familiar, or at worst, all but forgotten the traditional tools used in the alignment of  telescope optics; tools such as the collimation cap and the Cheshire eyepiece, and in so doing have less and less understanding of how their telescopes actually work.

The desire for super-accurate collimation has undoutedly been fuelled by the advent of faster optical systems; often supporting sub-f/5 primaries. Once, the traditional Newtonian was almost invariably made with higher f ratios:- F/7 to f/10 and beyond, and requiring very little in the way of maintenance. This is abundantly evidenced by the scant attention astronomy authors of the past gave to such pursuits. In contrast, modern Newtonians are usually f/6 or faster, necessitating much greater attention to accurate optical collimation if excellent results are to be consistently attained during field use.

In my chosen passtime of double star observing, I have acknowledged the need for accurate collimation. Such work often requires very high magnifications; up to and in excess of 50x per inch of aperture, to prize apart close double stars, some of which are below 1 arc second in angular separation. At such high powers, sub-standard collimation results in distorted images of stellar Airy disks, and that’s something that I’m not willing to put up with. In this capacity, I have tested a number of collimaton techniques using a few different laser collimating devices but have also spent quite a lot of time comparing such methods to more traditional techniques involviing the tried and trusted collimation cap and Cheshire eyepiece.

To begin with, it is important to stress that the methods covered in this blog can be achieved easily with a little practice, and I will gladly defer to recognised authorities in the art of Newtonian collimation, such as the late Nils Olif Carlin and Gary Seronik, who have done much to dispel the potentially stressful aspects of telescope collimation. Nothing I will reveal here goes beyond or challenges anything they have already said. My goal is to reassure amateurs that one can happily live without lasers, especially if your Netwonians are of the f/5 or f/6 variety.

Many of the entry-level laser collimators often manifest some issues; partcularly if they are not collimated prior to use. Thankfully, the inexpensive SkyWatcher Next Generation that I have used for a few years did come reasonably well collimated, but others have not been so fortunate. One easy way to see if your laser collimator needs collimating is to place it in the focuser of the telescope and rotate it, examining the behaviour of the beam on the primary. If the beam does not stay in place, but traces out a large annulus, you will have issues and will need to properly collimate the laser. This is not particularly difficult to do and many resources are available on line to help you grapple with this problem. See here and here, for examples.

Of course, you can pay extra for better made laser collimators that are precisely collimated at the factory. Units that have received very good feedback from customers include systems manufactured by Hotech, AstroSystems and Howie Glatter. Some of these are quite expensive in relative terms but many amateurs are willing to shell out for them because they deliver consistently good results. My own journey took me in a different direction though. Instead of investing in a top-class laser collimator, I re-discovered the virtues of traditional techniques involving the collimation cap and Cheshire eyepiece.

My personal motivation to return to traditional, low-tech tools was stoked more from a desire to understand Newtonian telescopes more than anything else. Any ole eejit can use a laser collimator but it deprives you of attaining a deep understanding of how Newtonians operate. In addition, I have frequently found myself dismantling whole ‘scopes in order to get at the mirrors to give them a good clean and this meant I had to learn how to put them back together from scratch. The simpe collimation cap has been found to be an indispensable tool in this regard, allowing one to rapidly centre the secondary mirror in the shadow of the primary.

Singing the virtues of simple tools, such as the tried and trsuted collimation cap.

 

Using just this tool, I’ve been able to set up all my Newtonians rapidly to achieve good results from the get go, at both low amd medium powers more or less routinely.

For the highest power applications  more accuracy is required and I have personally found that a quality Cheshire eyepiece to be more than sufficient to accurately align the optics in just a few minutes. Not all Cheshires are created equal though; some are less accurate than others. For my own use, I have settled on a beautifully machined product marketed by First Light Optics here in the UK ( be sure to check out the reviews while you’re at it). For the modest cost of £37, I have acquired a precision tool to take the hassle out of fine adjustment. The unit features a long sight tube with precisely fitted cross hairs that are accurately aligned with the peep hole. It needs no batteries and comes with no instructions but with a little practice, it works brilliantly!

The beautifully machined and adonised Cheshire eyepiece by First Light Optics, UK.

A nicely finished peep hole.

The precisely positioned cross hairs on the under side of the Cheshire.

 

Because all of my Newtonians are of the closed-tube variety, they are robust enough to only require very slight tweaks to the collimation. I would estimate that 80 per cent of the time, it is only the primary mirror that requires adjusting in field use. I have found this overview by AstroBaby to be very useful in regard to using the Cheshire and would recommend it to others.

The Cheshire eyepiece is a joy to use when collimating my 130mm f/5. Because the tube is short, I can access both the primary and secondary Bob’s Knobs screws to whip the whole system into alignment faster than with my laser. With my longer instruments; partcularly my 8″ f/6 and 12″ f/5, collimation using the Cheshire is decidely more challenging as they both have longer tubes. That said, by familiarising one’s self with the directions of motion executed with the three knobs on the primary, one can very quickly achieve precise collimation. One useful tip is to number the knobs individually so that you can dispense with the guesswork of which knob to reach for to get the requisite adjustment. At dusk, with the telescopes sitting pretty in their lazy suzan cradles, and with the Chesire eyepiece in place in the focuser, I swing the instrument back and forth to alternately view the position of the primary in the eyepiece and the knob(s) I need to turn. Doing this, I get perfect results in just a few minutes; a little longer than can be achieved with a laser, admittedly, but not long enough to render the process exhausting or boring. It’s time well spent.

Know thy Knobs: by spending some time getting to know which directions each of the collimation knobs move the primary mirror, it makes collimation with a Cheshire eyepiece hassle free.

The proof the pudding, of course, is in the eating, and in this capacity, I have found the Cheshire to achieve very accurate results each time, every time. Indeed, it has made my laser collimator blush on more than a few occasions, where high power star tests and images of close double stars reveal that the laser was out a little, requiring a collimation tweak under the stars. Indeed, the Chesire is so accurate that it has become my reference method to assess the efficacy of all the laser collimators I’ve had the pleasure of testing.

While I fully acknowledge the utility of good laser collimators, I get much more of a kick out of seeing, with my own eyes, how all the optical components of the Newtonian fall into place using the Cheshire. Furthermore, the fact that it requires no batteries (and so no issues with the unit failing in the field for lack of power, as has happened to me on more than a few occasions), deeply appeals to my longing for low-tech simplicity in all things astronomical. The fact that the aforementioned amateurs also recommend the Cheshire as an accurate tool for collimating a Newtonian makes it all the more appealing.

Having said all this, the utility of a Cheshire eyepiece lessens as the f ratio of your telescope gets smaller, so much so that for f/4 ‘scopes ar faster, the laser technique will, almost certainly, yield more accurate results. But that’s OK. We are blessed in this day and age with many good tools that can make Newtonian optics shine!

 

Note added in proof: August 14 2018

A really good laser collimator: the Hotech SCA, which can be used with both 1.25″ and 2″ focusers and comes in a very attractive little box with straightforward instructions on how to use it. You will still need the collimation cap to centre the secondary though.

 

If you do decide that you don’t like using a good Chesire eyepiece for precise collimation of your Newtonian reflectors, then I would highly recommend the Hotech SCA laser collimator. It’s an ingenious device (but costs significantly more than a regular laser collimator), but in this case you really do get what you pay for. I have tested the device on all three of my Newtonians and it gives accurate and reproducible results that agree perfectly with the Chesire. It yields perfect star tests at appropriately high powers (I’d recommend a magnification roughly equal to the diameter of your mirror in millimetres for such field tests) both in focus and defocused. I’d go for it if you can afford it. You will still need the collimation cap to centre the secondary before use however. See here and here for more details.

Neil English is author of Choosing and Using a Dobsonian Telescope.

 

 

De Fideli.

Focusing on Focusers.

How to adapt the Skywatcher 200P focuser to attain better collimation, as well as easier inter-change between 1.25″ and 2″ eyepieces.

 

Newtonians are tinkerers’ telescopes; they appeal to amateurs who want to learn about optics and above all other designs, they respond well to a bit of TLC. Such is the case with my modified Skywatcher 8″ f/6 Newtonian, which I have steadily improved over the last few years to transform it into my dream telescope; a modest instrument that can do all things well, from ultra-high power double star observing, through lunar and planetary studies and onwards into wide-field, deep sky observing. If I had to own only one telescope from all the varieties that now exist, I’d choose this one in a heartbeat.

The best way to improve a telescope is to spend as much time with it in the field. How else can one even begin to understand whether or not an alteration is warranted?  In this capacity, I have clocked up hundreds of hours under the starry heaven inter-changing two inch, long focal length eyepieces for their shorter focal length counterparts, which are invariably in the 1.25″ format. But doing this in the usual way is frankly a bit of a chore. On my telescope, one has to remove the 1.25″ focuser housing, insert a two inch tube adaptor and then plonk in the big 2″ eyepiece. As you can imagine, this can get a bit fiddly on a dark night and cause needless interruptions to one’s observing schedule. Can this interchange be speeded up? Thankfully, the answer is yes!

The standard 1.25″ eyepiece adaptor that comes with every Skywatcher 200P Dob.

 

The first thing I did was to remove the standard 1.25″ eyepiece adaptor that comes with the telescope and replace it with an inexpensive 35mm extension tube, such as the one featured in the first image of this blog.

Next, I inserted an old Orion precision centring adapter into the 35mm extension tube, as illustrated below:

A very useful adapter: the Orion precision Centering Adapter seen inserted onto the top of the 35mm extension tube.

 

The precision centring adapter features a helical tightening mechanism that precisely centres any 1.25″ eyepiece in the focuser draw tube. This has immediate benefits to attaining ultra-precise collimation, as it removes the remaining wiggle room that would normally attend the insertion of a laser collimator in the standard 1.25″ eyepiece adapter.

Using the precision centring adapter improves the accuracy of collimation using a laser collimator or Cheshire eyepiece.

 

Once collimated, one can insert a 1.25″ eyepiece as shown below:

The centring adapter keeps 1.25″ oculars snug and precisely centred in the focuser drawtube.

 

To use 2″ eyepieces all one needs do is remove the centring adaptor, and insert the eyepiece into the 35mm extension tube as shown below:

Removing the centring tool is child’s play and allows for rapid interchnage with a 2″ ocular.

 

Testing this new system out during the day, I can report that it allows all my eyepieces; orthoscopics, Plossls, super-wide, ultra-wide angles and even Kellners to reach sharp and precise focus at infinity, as well as targets located as close as approximately 50 yards in the distance. It greatly facilitates the inter-change between 1.25″ oculars and their 2″ counterparts in the field because it always has the 2″ eyepiece adapter in the focuser drawtube. No more fumbling about in the dark.

So, if you’ve got these adapters lying about in your ole box of tricks, I’d encourage you to give it a go. It can only serve to increase your enjoyment of a very fine telescope. You know it’s worth it!

Octavius: working more efficiently for its master.

 

Note added in proof (August 2 2018):  I’ve managed to get out on a few nights before the weather turned and test the new configuration on both my 8″ f/6 and 12″ f/5 instruments (both of which are endowed with 2-inch focusers) under rapidly darkening skies. I can report that the alteration was definitely worthwhile!. The centring adapter is very easy to remove or insert at will, allowing me to go from wide-field scanning at low power, using heavy, 2-inch eyepieces covering a couple of angular degrees of sky or more, and then zoom in at inceasingly high powers, sometimes much beyond 50x per inch of aperture, to look at high resolution stuff.

All in a jiffy!

One downside noted: some(but not all) Barlowed oculars can’t come to focus with this modus operandi.

No’ bad ken.

Neil English is author of Choosing and Using a Dobsonian Telescope.

 

De Fideli.

 

Sampling the Skies in Ireland with a 5.1 inch Newtonian.

Plotina: the author’s 130mm f/5 travel Newtonian enjoying the skies over Cork Habour, Cobh, County Cork, Ireland.

 

July 9 through 21, 2018

It could have been altogether very different.

Having access to a suite of small, portable instruments, like a fine 90mm ED refractor, a first-rate 80mm f/11 achromat, an ETX 90 and a 90mm f/10 achromat, I’m so glad I threw tradition to the wayside and brought along my 130mm f/5 Newtonian telescope on my recent trip to Ireland. As described exhaustively in several previous blogs, the latter instrument is a superior grab ‘n’ go telescope to all of the above instruments on all targets; whether in the Solar System or far beyond. Its mirrors efficiently bring light to a sharp focus and with a relatively small central obstruction (27 per cent), it behaves more like a 5 inch refractor than anything else. Yet it is very lightweight, easy to collimate accurately and, as demonstrated previously, delivers excellent images of planets, the Moon and very tight double stars down to 0.94 seconds of arc: the absolute limit imposed by its 130mm aperture. And, as will be described shortly, it’s not too shabby as a rich field/deep sky instrument either.

These findings were all  previously established in many parts of the Scottish mainland and even on some of the Western Isles, but I was especially keen to see how the telescope would fare at no less than five locations in Munster, the southern-most province of the Irish Republic. I have very fond memories from youth using much smaller instruments, but the 130mm Newtonian promised to reveal much more.

The Journey

The telescope was carried in a sturdy aluminium case in the boot of my car from my home in central Scotland down to southern Scotand, and then by ferry across to Northern Ireland, and from there, southwards to the Republic; a day’s trip.

Upon arrival, the telescope was found to be very slightly out of collimation but a laser collimator made light work of tweaking the optics in a matter of seconds.

Locations tested:

Limerick City: Ballinacurra in the southwest of the city & Caherdavin, a few miles away on the other side of the great River Shannon, in the northwest of the city.

Cobh, County Cork.

Sixmilebridge, County Clare.

Newport, County Tipperary.

 

Conditions: Over ten days, only two nights turned out cloudy, the rest being either fully clear or partially clear. At all locations, true darkness occurred around local midnight, remaining so for about two hours. In general, all observations were conducted on grass, as this was established to be the best surface upon which astronomical observations should be made.

Eyepieces used: Just two oculars were chosen for the trip; a Celestron X-Cel 25mm, delivering a power of 26x in a 2.3 degree true field, and a Meade Series 5000 5.5mm ultra wide angle, serving up a power of 118x in a 0.7 degree true field. Additional powers of 59x and 266x could be pressed into service by attaching a Baader 2.25x Baader shorty Barlow to the 25mm and 5.5mm eyepieces, respectively.

Telescope mounting: The 130mm f/5 is a perfect match for the Vixen Porta II Alt-azimuth mount, which travelled with me along with the telescope. High magnification targets were tracked with ease using the in-built slow motion controls.

Results on the Planets: Planetary views of Jupiter and Venus were conducted earlier in the evening. Mars was not viewed owing to its very late culmination well into the wee small hours of the morning.  The extra 4 degrees of elevation in the sky owing to the sites’ lower northerly latitude (centred around 52 degrees north), proved significant; Jupiter showed a wealth of detail using the 5.5mm Meade ultrawide angle ocular delivering 118x. Much dark banding and subtle colour differences within the bright zones could be discerned. The North Equatorial Belt (NEB) was very prominent throughout all the vigils, being noticeably darker and more disturbed morphologically than its southern counterpart. On one evening, I was able to accurately establish the CM II longitude of the Great Red Spot and the finest images of Jupiter were afforded at Newport, County Tipperary, with the telescope set up on tarmac owing to a lack of a suitable grassy surface, but the relatively high elevation of the shorttube 130mm reflector astride the Viven Porta II above the surface proved an effective dampener of thermals, even though the same day and evening were hot and sunny.

Venus showed its pretty, early gibbous phase at 118x in the telescope, despite its very low altitude at the times of observation. Some atmospheric refraction yielded some false colour but this was expected and largely unavoidable.

The Moon:

On Thursday, July 19, I shared some magical moments with my elder brother, who lives in Newport, County Tipperary. Around sunset, I set the instrument on the tarmac ouside his house and aimed it at a late crescent Moon. The view in the 5.5mm Meade delivering 118x was amazing; my brother being deeply impressed at seeing the entire lunar regolith  in razor-sharp detail, floating through the huge portal hole. At first he couldn’t help but hold the eyepiece (a natural newbie reaction), but as soon as I taught him to let go, he just relaxed and let the telescope do the work. I could tell that he was quite taken aback with this strange little telescope, where you peer through its side rather than directly along the tube. With a few minutes training, he learned how to use the slow motion controls to bring Luna back into the centre of the field.

 Double Stars:

Test double stars examined included:

Epsilon Bootis ( Izar)

Delta Cygni

Epsilon 1 & 2 Lyrae

Pi Aquilae

Such systems were chosen for their sensitivity to ambient seeing conditions and ease of location, even from an urban/suburban setting.

Results: At every location examined, the results proved very much the same: all systems were beautifully resolved at 266x, the companions being perfectly picked off from their respective primaries. One location proved to be windy (overlooking Cork Harbour in Cobh), but this turned out to be largely inconsequential to the observations made. Once the wind died down, the companions yielded easily.

 

Deep Sky Observations:

General appearance of the sky after sunset, as witnessed on a few evenings during the vacation. Such cloud formations augur good, stable summer air.

 

Naked Eye: I immediately noticed the lower elevation of the Pole Star than at home.

I recorded three bright fireball-like meteors streaking across the sky (2 on one evening, the other on a subsequent evening)  from the direction of Cassiopeia/Perseus. These were possibly early Perseid meteors, which will culminate around the middle of August.

Even from a suburban location (Caherdavin), the sky got dark enough to easily see magnitude +4.6, Iota Cassiopeiae, low in the northeast, which was not possible from my Scottish vantage owing to the encroach of twilight. From the same location, I was able to trace out the more prominent parts of the Northern Milky Way streaming through Cygnus and Cassiopeia.

The darkest skies were experienced at Cobh, which is not too surprising, but there was still a significant amount of light pollution from the adjacent harbour to the southwest of my viewing location. Still, magnitude +5.8 Messier 13 could not be seen owing to this light pollution despite its high elevation in the southwest at the times of observation.

Telescopic Impressions:

The 5.1 inch reflector set up for an observing session at Sixmilebridge, County Clare.

The 25mm Celestron X-Cel LX eyepiece proved very satisfactory with the 130mm f/5 reflector, delivering sharp, high-contrast images of star fields nearly all the way to the edge of its 2.3 degree field. I enjoyed studying the stellar hinterlands of bright stars within Cygnus, particularly Sadr and Deneb, the truly dark skies pulling out a wealth of fainter stars frankly invisible in the twilight of Scotland.

M39 in northern Cygnus was pariticularly captivating in the 25mm wide field eyepiece at Caherdavin; a rich smattering of approximately three dozen suns of the 7th magnitude of glory and fainter, arranged in a neat triangular space approximately 30′ in size. The Barlowed view with the same eyepiece at 59X was much more immersive though. M29 was dull in comparison; small wonder my guide book has nothing to say about it lol!

The 5.5mm Meade ocular was by far my most used ocular during the trip. Having become somewhat disillusioned by high-quality, small field of view oculars, such as the Vixen HR series, with their measly 40 degree fields, I very much appreciated the vastly more expansive (yet very well corrected) fields afforded by this 82 degree ocular. Such short focal length, wide-angle eyepieces are a godsend to those who enjoy manually tracking tight doubles. They are visible for longer, allowing the observer much more time to examine their morphology before having to nudge the telescope along.

The 5.5mm served up excellent, immersive views of showpiece summer deep sky objects such as M13, M92 and M57, the 118x power really helping to darken the sky. The view of M13, in particular, was most impressive, even from suburban locations, comparing very nicely with my 5″ f/12 refractor from my recollections. The outer part of the globular was well resolved with dozens of stars seen directly or by using averted vision.

The same eyepiece is especially good at observing wide ‘binocular’ doubles such as Albireo, 61 Cygni, Gamma Delphini, Beta Lyrae and the incomparable 31 (Omicron) Cygni, all of which were enjoyed with the telescope at most of the sites visited.

At 23:30 UT on the evening of July 16, I aimed the telescope from suburban Limerick (Caherdavin) at Iota Cassiopeiae, then located just above the tree line of the garden. To my sheer delight, I was able to clearly see the three components of this trple system using the Meade ocular at 118x. This was a particularly impressive observation, owing to the fairly low power employed but also because of its low elevation at this site. This is a powerful testimony to the excellent stability of Irish suburban skies.

I enjoyed some special time exploring the rich treasures of the far northern constellation of Cepheus on the evening of July 16, which is drowned out by twilight in Scotland. Delta Cephei was very captivating at 118x. The primary is an old, yellow pulsating Cepheid variable( the prototype of this stellar class) with a gorgeous blue companion; a near twin of the more famous Albireo. Xi Cephei  presented beautifuly also; its blue white and yellow suns well resolved at 118x. Omicron Cephei was also briefly visited; easily resolved at 118x but better seen at 266x; its magnitude +4.9 ochre primary and much fainter (magnitude +7.3) steely grey companion being readily observed. Then, there is the incomparable Mu Cephei, an enormous red giant star, its deep sanguine hue standing out like a sore thumb against a good, dark sky was a sight for sore eyes. Mu is comely at low or high power in the 130mm reflector.

Don’t forget Saturn!

Almost forgot!

Though it was past their bedtime, I showed my boys the planet Saturn for the very first time, located well east of Jupiter and only becoming visible to the naked eye very late in the evening. Being even lower in the sky than brilliant Jove, the telescope still did a mighty good job at 118x showing them the mottled globe of the planet, with its beautiful, icy-white ring system, the Cassini Division being easily dicsernible at a glance. The view at 266x was not so good though; a simple consequence of the blurring effect of the Earth’s atmosphere at this low altitude. Still, I showed off Saturn to friends and family where ever possible. Of all the celestial objects studied, it was the Ringed Planet that received the most oohs and aaws!

Concluding Thoughts

The experience of a truly dark sky in mid-July was a joyous event for me; accustomed as I am to ferreting out things to see in twilight at home in Scotland. The small Newtonian proved to be the perfect travelling companion, its generous aperture, light weight and easy set-up all helped to make the trip memorable and worthwhile. In many ways, Ireland is a transformed nation now (it would be naive not to think so); sadly, it has sleepwalked its way into the pernicious mire of secularism, with all its attendant depravities. But at least the skies overhead are still good to go, a comforting reminder of God’s incomparable glory and omniprescence. Though I would like to have visited a site completely devoid of light pollution it was not to be on this occasion, yet conditions were near ideal during these eight days of observations (especially for high-resolution, double star work), but surely many more such evenings occur on the Emerald Isle?

And I’d do it all again in a heartbeat!

 

Neil English is author of a large and ambitious work; Chronicling the Golden Age of Astronomy, due out later in 2018.

 

 

De Fideli.

Going from Strength to Strength: the 130mm f/5 Newtonian.

Plotina: queen of grab ‘n’ go ‘scopes.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I’ve spoken quite extensively on the considerable virtues of my modified 130mm (5.1- inch) f/5 Newtonian with a 27 per cent obstruction. In contrast to the prognostications of fake theorists and arm-chair amateur astronomers, it has proven to be a fantastic all-round ‘scope, easily trouncing smaller grab ‘n’ go refractors and equivalent sized Maksutovs costing significantly more. It provides very pleasing wide field views at low magnification and excellent performance at high magnifications, especially on a suite of double stars, the Moon and bright planets.

As a double star enthusiast, I have managed to split systems down to one second of arc with this telescope during the winter months but in theory it ought to do a little better. Specifically, the classic Dawes limit for this aperture is given by 4.57/5.1= 0.89″ but is confined to pairs which are reasonably matched in terms of brightness. In this capacity, I was curious to see whether I could resolve the very challenging Lambda Cygni, with a current separation of 0.92″, the components of which differing only by 0.4 stellar magnitudes(5.4 and 5.8).

Taking full advantage of the hot, settled spell (Scorchio lol!) that is currently being enjoyed by residents of the British Isles, I eagerly sought out a system I’ve visited many times before, but mainly with my larger instruments (8″ f/6 and 12″ f/5 Newtonians). I speak of course, of that easily accessible system riding high in my summer sky after midnight during June evenings; Lambda Cygni.

This magnitude 4.5 system is easy to track down, even in twilight, and in preprartion, I have been monitoring an easier system; Pi Aquilae, located much lower down in the east south east at this time. My reasoning was simple; if this lowly system was well presented at high powers in the 130mm instrument, there would be a decent chance that Lambda Cygni would also bear fruit. But that proved to be easier said than done. Over several nights, both this week and last week, I have carefully studied the system but invariably recorded strong elongation. Yet in double star observing, as in so many other arenas of human enquiry, it pays to persevere; and finally in the wee small hours of June 27 2018, I won my prize!

At half past midnight, I noted an exceptionally stable and well resolved Pi Aquilae at powers of 260x and 406x and excitedly turned my telescope on Lambda hoping for a better result. And at 2 minutes past 1am local time, it yielded. Letting the system drift through the field several times over a period of a few minutes I could make out two distinct Airy disks intermittently separated by a delicate sliver of dark sky using a power of 406 diameters!

To put this in context, I have previously just resolved this system using a fine 127mm f/12 achromatic refractor at very high magnifications. And though my recollections show that it was that little bit better at ferreting out the pair, it was always very challenging and only possible under similarly clement conditions. So a most satisfactory result, but not at all violating the rules of classical optics. If something is possible, it will happen; you just have to be there to experience it!

I made a drawing of what I observed at the eyepiece( shown below);

Shumbody stop me!

I’ve been thinking about the eyepieces I wish to bring on our summer vacation and decided to treat myself to an upgrade to my trusty 32mm Plossl. To that end, I gravitated toward the Explore Scientific 24mm 68 degree ocular, which would provide a power of 27x in a 2.5 degree field (the maximum possible for a 1.25″ focuser). So I ordered one up for the princely sum of £142 plus shipping. I had very high expectations about this eyepiece judging by the excellent performance of two other 68 degree Maxvision oculars ((34mm and 40mm also marketed by Explore Scientific) I have already field tested. Both of these provide very highly corrected fields across a very expansive field and provide excellent eye relief for maximum viewing comfort. The eyepiece was ordered on Monday June 25 and it arrived in the early evening of June 27.

The Explore Scientific 24mm 68 degree ocular.

As soon as it was getting dark, I fielded the 130mm f/5 Newtonian once again in order to test the new eyepiece out. Centring Vega in the field, I focused the image and to my chagrin, I noted pretty harsh field curvature and coma in the outer part of the field. When Vega was sharply focused at the edge of the field, the stars in the periphery of the field were quite badly out of focus. This was patently not the result I expected for such a pricey eyepiece. What is more, the eye relief was pretty poor too. I had to bring my eyeglasses right up to the field lens, with the ruuber eyecup pushed down, to try to take in the entire field but it was barely possible and far from comfortable. “As tight as a knat’s chuff” is an expression that immediately sprang to mind lol!

When I compared it to my 32mm, the eye relief was far more comfortable (being about 0.73 times the focal length in millimetres, so ~ 23mm) and though the magnification was slightly lower (20x) the Plossl proved significantly better corrected at the edge of the field!

Was I disappointed? You bet I was! I don’t know if I received a lemon or not but on the morning of June 28 2018, I phoned the dealer and explained that the eyepiece did not perform as advertised and that the 32mm Plossl I tested alongside it delivered better performance. Thankfully, they gave me the go ahead to send the eyepiece back so they could test the unit out. I expect a full refund in due course.

What a palaver!

Anyway, while thinking about my next move on the low power eyepiece front, I intend to bring my trusty 32mm Plossl on my vacation, together with my old Mark III 8-24mm Baader Hyperion zoom. This will provide all the medium power viewing I will likely do, and the 2.25x Baader Barlow will enable me to increase the power to 183x; good enough to study quite a few double stars under dark, Hibernian skies.

Travelling light ( from left to right); my 32mm SkyWatcher Plossl, 8-24mm Baader Hyperion zoom and dedicated 2.25x shorty Barlow.

 

After several more nights of observation with the 130mm f/5 Newtonian, I managed yet another sighting of the companion to Lambda Cygni. Specifically, on June 30 at 23:20 UT, using the same power of 406x, the stars were seen cleanly separated on and off during several minutes of observations. With the fine weather continuing for UK observers, I would warmly encourage others with instruments of 5 inches and over to have a go at this system at high powers. It’s very accessible with an 8″ f/6 Newtonian (confirmed once more around local midnight on July 1/2)

The Explore Scientific eyepiece arrived safely back at the dealers this afternoon (July 2 2018). I am now considering the Celestron 25mm X-Cel LX, which is purported to work well in f/5 optical systems and with a 60 degree AFOV should give nice, expansive views, well over 2 degrees in extent.

 

July 4th 2018: A Very Happy Independence Day to all my viewers in the Colonies!

We leave for Ireland on Monday next, July 9. I’m very excited about sampling the skies of my youth with my 130mm f/5. Of course, I’ve had other telescopes over there, back when my folks were still in the land of the living; a 90mm f/10 achromat (which is still at my sister’s home), and when the ETX 90 was all the rage in the late 1990s, I astounded my late father with its go-to capability and almost magical ability to centre and track down the planet Jupiter in the field of view one chilly Christmas Eve.

Plotina being readied for another night of sky gazing.

 

Bringing a Newtonian is a big change for me. It was always a small refractor or Mak that made it, but this time ’round, I can think of no better telescope to enjoy my vacation with. My wife got a bit of shock when I told her I’d be lugging the 130 in its case, but she has since come round to the idea of having me put all my astro junk in one neat place lol..

I’m relatvely new to Newtonians you see. I pretty much overlooked them, owing to the rise of refractor mania and catadioptrc telescopes in the last few decades. I did have one in my youth however; my second telescope, a Tasco 114mm (4.5-inch), f = 900mm or some such that came in a big yellow box decorated with fabulous photos of planets and deep sky objects. Back then though, I knew next to nothing about the rigours of fine collimation, or how to precisely align its equatorial mount(non-motorised). I bought it second hand from a jeweller that lived near me. It cost me £100; an enormous sum of money for a young teenager in the early 1980s. I eventually sold it on to raise some funds for University a few years later.

Still, the 130mm is far superior in many ways to that old Tasco; greater aperture, light gathering power and sharper optics owing to its nicely figured parabolic mirror. No fooling around with complex mounts either; just stick it on the Vixen Porta II and I’m off to the races! Eyepieces have improved vastly as well; the Tasco came with two cheap Huygenians and a junk Barlow lens.

Mars’ fiery red mien graces my horizon after midnight and Jupiter is quite a bit past opposition, but I hope to get a better view of both worlds as they will rise a few degrees higher in the sky than they do here in rural central Scotland. And having the chance to explore the vast skyscape within the confines of the Summer Triangle (marked by Vega, Deneb and Altair) from a truly dark sky will be an enjoyable experience. That said, last night I lingered a while on a reasonable view of the Ring Nebula in Lyra with my 34mm widefield and 8-inch reflector in summer twilight. How much better will the views be under true July darkness?

I decided to pull the trigger on a Celestron X-Cel 25mm LX eyepiece, which should arrive here by Friday. Fingers crossed for reasonable performance in the f/5 optical system!

The sky is darkening more now as the days and weeks have flown by the Solstice. The stars of Delphinus are beginning to show in the deep twilight and so a chance to visit another summer favourite; the delightful colour contrast pair, Gamma Delphini.

After midnight on July 5 2018, I began searching for two systems; Gamma Delphini and Mu Cygni. The latter proved much more challenging to track down, even with the Celestial Swan now having gained a considerable altitude. Gamma is widely spaced and presents with an aureal primary and lemon-white secondary. Mu is much more challenging though, especially at this time of year; the secondary is situated right up next to the primary but the great light gathering power and resolution of this grab ‘n’ go telesope on steroids made light work of it at 260x but the view was even more compelling at 318x. It’s such a delicate system to study telescopically; like budding yeast seen through a powerful microscope. I made a couple of drawings of what I saw (shown below):

Two gems of the summer twilight: Gamma Delphini & the challenging Mu Cygni, as seen through the 5.1″ f/5 Newtonian in the wee small hours of July 5 2018.

 

July 6 2018

The Celestron 25mm X-Cel LX 60 degree eyepiece.

 

Well, the new 25mm Celestron X-Cel LX eyepiece arrived late this evening. It was packaged well and a quick inspection revealed no internal dust in the optical train. It is very light, considerably less so than the 24mm Explore Scientific (ES) 68 ocular I sent back to the dealer and that’s a bonus, given the low mass of the optical tube. Like the Baader zoom, this eyepiece has a twist-up eyecup which allows the user to adjust the distance between the large eye lens and the eye. Testing it on the telescope in the bright evening sunshine revealed some very good things; the image of a distant rooftop was very sharp. Constrast was excellent. It showed a very small amount of field curvature and/or distortion at the edge of the field but best of all the eye relief was just right; that is, I was able to comfortably view the entire field with my eyeglasses on, in sharp contradistinction to the ES 68. Things were indeed looking good.

The Celestron 25mm X-Cel eyepiece has a large eye lens and twist-up eye cup for optimal viewing pleasure.

Around local midnight, I was able to test the new eyepiece on the stars. I am happy to report that it produced very sharp images of Vega and its hinterland, with good contrast and, to my relief, off axis performance was much better than I had experienced with the 24mm ES 68. Nor did I detect any internal reflections. There was a liitle distortion at the edge of the field but it was more than acceptable, certainly a notch up from the 32mm Plossl I have used for so long with the instrument. And like my daylight experiences, the eye relief was more than adequate when used with my eye glasses(which corrects for the natural astigmatism in my viewing eye).  This improved perfomance may at least in part be attributed to the smaller AFOV of this eyepiece (60 degrees as opposed to 68 degrees with the 24mm ES) but maybe also to its design differences. Nevertheless, I am more than content with its optical performance as a low-power, wide-field scanning ocular, delivering a power of 26x in a true field of 2.3 degrees. And in consideration of the fact that it set me back just half the price of the 24mm ES 68 (£70), I think it represents a really good bargain.

Technology has come a really long way since the days of my youth.

A happy camper am I.

 

At 00:45 local time on Saturday July 7, I turned the telescope toward Cassiopeia, now low in the northern sky and washed out quite a bit by the presence of twilight. I used my 6 x 30mm finder on the 130 to track down the creamy white magnitude +4.6 star, Iota Cassiopeaie. Ordinarily, I wouldn’t go near such a system at this time of year owing to how bright the sky is, but the persistant good weather here inspired me to give it a go. From memory, this star is annexed to a triangular configuration of three fainter stars so it was easy to identify. This is a famous triple system and its delicate cast under good conditions never fails to impress. I was pleasantly surprised with how well it presented at 260x, with all three members showing up clearly and distinctly. I made a quick sketch of what I recorded in the small Newtonian telescope, and is shown below. This is well worth a try at high northern latitudes in small telescopes with easy access to the northern horizon.

 

Iota Cassiopeiae as seen at 23:45 UT on the night of July 7th 2018 using the 130mm F/5 Newtonian at 260x. Note that the date should read July 7 and not July 10. Mea culpa.

 

I spent the afternoon of July 7 2018 deliberating about which eyepieces to bring and which to leave behind. The new 25mm Celestron is definitely coming on the trip. Further daylight tests showed that it Barlows real well with the 2.25x Baader shorty Barlow giving a nice medium power of 59x in a one degree true field. I have had second thoughts about the Baader zoom though, as it’s a bit on the heavy side and even with the same Barlow would only yield 183x, grand for most systems but since the telescope can very comfortably accommodate 50x per inch of aperture, I wished to coax that little bit more power out of the instrument. Racking my brains, I pulled out an older eyepiece which I had boxed away under my bed; a Meade Series 5000 5.5mm Ultra-Wide Angle (82 degree field). As I’ve said in a previous blog, I’m not overly enamoured by 82+ degree AFOV oculars, preferring 60 to 70 degree units in my field work, but upon testing it out in the 130mm f/5 Newtonian on a bright sunny day, I was quite impressed with what it delivered. A high-end eyepiece like this has very good edge-of-field correction and yields a power of 118x in a field of 0.7 degrees. Coupled to the 2.25x Barlow I can squeeze a high power of 266x out of it; perfect for the most challenging doube stars should they present themselves!

So, in the end, two eyepieces, both significantly lighter than the Baader zoom, will be coming on the trip with me, together with a single, 2.25x shorty Barlow. That combination will tick all the boxes!

Final choice (left to right): the Celestron 25mm X-Cel LX, the Meade 5.5mm Ultra Wide Angle and the 2.25x Baader short Barlow lens.

 

This is a good place to wrap up this blog. Take care and see you all when we get back in a couple of weeks.

 

All the best,

 

Neil.

 

 

 

De Fideli.

Observing in Twilight.

A great ‘scope to use in twilight; the author’s 130mm f/5 Newtonian which combines light weight with good optical power.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

At my northerly latitude (56 degrees north) every year from about the middle of May to the first week in August, the sky fails to get properly dark and twilight dominates the northern horizon. As a result, the glory of the summer night sky greatly diminishes, with only the brightest luminaries being visible to the naked eye. But despite these setbacks, one can still enjoy a great deal of observing. In this article, I wish to outline some of the activities I get up to during this season.

Observing in twilight makes observing faint deep sky objects very difficult, so my attention is drawn to the Moon, brighter stars and the planets. Although a telescope of any size can be used during twilight observing, I find it most productive to field a telescope that has decent aperture and so I generally reach for my larger telescopes. Arguably my most used instrument during these times is a simple 130mm f/5 Newtonian, which offers good light grasp and resolution but I am also very much at home with my larger 8 and 12 inch reflectors for more specialised work. The 130mm has the advantage of being light and ultraportable and so I can move the instrument around to get better views of low lying targets.

The bright planets are very accessible during twilight and I find it fun to observe them with a variety of instruments. Venus is generally uninspiring, showing only an intensely white partial disk, but I find Jupiter much more exciting owing to its constantly changing atmospheric features and satellite configurations. But because of its low altitude in my sky, I employ colour filters to bring out the most details on the planetary disk. This is where larger apertures have their advantages, as some filters can absorb a significant amount of light and dim the images too much. The sketch below was made during twilight using my 130mm f/5 and a Tele Vue Bandmate planetary filter, power 108x, which imparts a lively colour tone to the planet, enhancing the colour differences between the dark belts and light zones. It’s also an ideal filter for enhancing the visibility of the Great Red Spot(GRS).

Jupiter as observed durng twilight at 22:55 to 23:05 UT on the evening of May 28 2018 using a 130mm f/5 Newtonian, magnification 108x and a Televue BPL filter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Twilight nights are also excellent for double star work and summer often brings prolonged periods of excellent seeing at my location. Larger apertures allow higher magnifications to be pressed into service, which also helps to darken the sky making the views more aesthetically pleasing. As in all other aspects of amateur astronomy, you can be as ambitious as you want. The most demanding systems are difficult, sub arc second pairs. As a case in point, I recently trained my 8 inch f/6 Newtonian on 78 Ursae Majoris (78UMa), conveniently located near the bright star, Alioth, in the handle of the Ploughshare. Conditions were near ideal on this evening (details provided in the sketch below) and I was able to push the magnification to 600x to splice the very faint and tight secondary star from the brighter primary.

The sub arc second pair 78 Ursae Majoris 78 as seen in twilight on the morning of May 30 2018 at 23:20UT using an 8″ f/6 Newtonian reflector (no fan).

Another system that I like to re–visit in summer twilight is Lambda Cygni (0.9″), which is easier to resolve than 78UMa, as the components are more closely matched in terms of their brightness and are slightly farther apart. Because it rises very high in my summer sky, it is ideally placed for high magnification work.

Conducting sub–arcsecond work with an undriven Dob mount is certainly not for the faint hearted but does bring its unique challenges, and I for one get a buzz out of doing this kind of work. But there are many easy and visually stunning systems that can be enjoyed at lower powers and it is to some of these that I will turn my attention to in the coming nights.

Last night (the early hours of June 2 2018) my wonderful little 130mm f/5 Newtonian was used to visit a number of easy to find and visually engaging binary and multiple star systems. During warm, settled weather, and with high pressure in charge, the twilight conditions proved near ideal for studying these fascinating objects;

Some binary systems visited in twilight using a 5.1″ f/5 Newtonian.

 

 

 

 

The celebrated Double Double in Lyra as seen through the 5.1 inch reflector at 260x.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The very fetching Epsilon Bootis as seen in the 130mm f/5 Newtonian at 260x.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

These observations were conducted between 23:00UT and 00:00 UT.

Indeed, of all my Newtonians, it is the 130mm f/5 that provides the most aesthetically pleasing views of double stars. Colours are always faithful and images are invariably calm owing to its moderate aperture and rapid acclimation. Contrast is excellent too. It just delivers time after time after time…..

The sky as experienced 15 minutes before local midnight on the evening of June 12 2018.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

As May turns to June, the twilight becomes ever brighter, with more and more stars becoming invisible to the naked eye. But this greater sky brightness should never deter a determined observer. On the evening of June 12 2018, I set about visiting a score of  double and multiple stars with my 130mm f/5 Newtonian, as is my custom. I turned the telescope toward Polaris at 22:45 UT  and was deligted to be able to pick up the faint 8th magnitude companion to the 2nd magnitude Cepheid primary. Looking for something more challenging, I waited another half an hour to allow the sky to darken maximally but also to allow a summer favourite to gain a little altitude but still several hours away from culmination in the south. I speak of that wonderful binary system, Pi Aquilae( Aql), a pair of yellow white stars of near equal brightness and separated by about 1.5 seconds of arc.

From extensive, previous experience, I know it is possible to split this pair in smaller telescopes than the 5.1 inch reflector, particularly a suite of refractors ranging in aperture from 80mm to 102mm. But under these June conditions, the advantages of decent aperture become readily apparent; smaller telescopes simpy run out of light too quickly when the high powers needed to splice this pair are pressed into action. Locating the 6th magnitude pair at a fairly low altitude under bright June twilight  is even a challenge for the 6 x 30mm finder astride the main instrument. To my delight though, I was able to track it down and once centred, I cranked up the power to 325x ( using a 2mm Vixen HR ocular) to obtain a marvellous view of this close binary system, the components aligned roughly east to west with clear dark space between them. Adopting these powers with smaller apertures is problematical to say the least. Why strain one’s eyes when one can view it in much greater comfort using the generous aperture of this trusty 130mm grab ‘n’ go ‘scope?

I made sketeches of both Polaris A & B and Pi Aql as I recorded them at the eyepiece (see below).

Polaris A & B and the tricky, near equal magnitude pair, Pi Aql, as seen in the 130mm f/5 Newtonian reflector on the evening of June 12 2018.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

As the June solstice approaches, the twilight continues to brghten the sky, but there’s still lots to see. Beginning about 10pm local time, I began observing a pretty crescent Moon sinking into the western sky. The instrument I chose this evening was a very inexpensive but optically excellent 76mm f/9.3 Newtonian reflector, which I described at length in previous blogs such as this one. Because our natural satellite is so big and bright, a small telescope like this one is ideal for casual observing. Because the sky is still quite bright at this time, I found it helpful to employ either a neutral density or variable polarising filter to increase the contrast between the lunar regolith and the background sky.

An amazing performer in June twilight: the Orion Space Probe 3 altazimuth reflector.

Observing the Moon in June twilight is fun at all magnifications, but I have discovered this little telescope can provide razor sharp images up to about 210x. You’ll not get this information from the telescope forums though; it still seems beneath them to test it and spread the word, but I digress!

On the evening of June 18 2018, I visited a suite of summer double and multiple stars with the same instrument.

At about 11.30pm local time, the sky was dark enough to track down some pretty tight double stars, as well as a variety of easier but just as comely systems. Conditions were good enough for the little Spaceprobe reflector to nicely resolve Epsilon Bootis, Epsilon 1 & 2 Lyrae and Delta Cygni (210x in each case). My study of the Lyra Double Double in particular with this telescope shows that it is significantly better than any 60mm refractor in terms of raw resolving power. As I have reported earlier this year, the same telescope was able to resolve Xi Ursae Majoris, Porrima, Eta Orionis, and the wonderful triple system, Iota Cassiopeiae. Sadly, the latter system, which is still present low in the northern sky in June, was hopelessly lost in the summer twilight. Bootes always presents a nice playground for easy and pretty double stars, including Kappa, Pi, Xi and Nu 1 & 2 Bootis, which were all easily split at 116x.

June is also high season for the beautiful, ghostly whisps that meteorologists refer to as noctilucent clouds. These thin, high altitude formations are lit up by the Sun while still below the northern horizon, creating quite surreal visual delights to the naked eye. I took a couple of low resolution images with my iphone (shown below).

Noctilucent clouds captured outside my house at local midnight on the evening of June 18 2018.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Another view captured at local midnight on the evening of June 18 2018.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I shall endeavour to capture some higher resolution shots of these wonderful meteorological structures in due course.

Plotina, the author’s amazing 130mm f/5 Newtonian reflector as seen at 11.10pm on the evening of June 21 2018.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

On the June Solstice of 2018, I  walked through the garden in the cool of the evening, fetching my trusty Vixen Porta II mount to field my 130mm f/5 Newtonian. A gentle westerly breeze was blowing and the sky was resolutely clear, but I have learned on many past occasions that these conditions often bring very good seeing conditions for high resolution double star work. And my efforts were rewarded with text book perfect images of a suite of difficult double stars, some of which I have mentioned earlier in this report. I also ended my year long evaluation of a variety of eyepieces and Barlow lenses,varying quite considerably in price range. These studies have led to some firm conclusions regarding the effects of moving air upon Newtonian optics, as well as some very surprising results concerning the efficacy of certain oculars in regard to resolving double stars. Do you always get what you pay for? Most certainly not!

Insofar as artificiallly blowing air on a Newtonian mirror has been shown to scrub off the so-called boundary layer immediately above the reflective surface, my field testing over many nights shows that natural wind can also improve the images in exactly the same way. For this reason, I invariably point the telescope into any prevailing wind while the telescope cools and this works especially well for my larger Newtonian reflectors (8- and 12 inches). Furthermore, I am not aware of any historical precedent for this; the work of some notable telescopic ancestors of the ilk of W.F. Denning, T.H.E.C. Espin, T.E.R. Philips, A.S. Williams, T.W Webb and N.E. Green ( the selected work of which I will feature in my up-and-coming historical work) all of whom used Newtonian reflectors to great effect do not explicitly give mention to this result, though there is no doubt it is generally true.

The Vixen HR series of oculars; nice but totally overkill for high resolution double star work in medium and large aperture aperture Newtonian reflectors.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

On many fine evenings using a variety of Newtonian telescopes, I have compared the views through top-of-the-range eyepieces, such as the new Vixen HR series of ultra-short focal length oculars(1.4mm, 2.0mm and 2.4mm) and those derived from much more modest (but still very good) Plossls and orthoscopics coupled to decent Barlow lenses and my conclusions are that the much more expensive eyepieces do not confer any real advantages over the latter.

Ordinary eyepieces and Barlows work perfectly well with Newtonian reflectors for high-resolution double star work. Left to right; a 3x Meade achromatic Barlow, a 7.5mm Parks Gold and Baader 6mm classic orthoscopic.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Yes, the HR series do display slighly better contrast and reduced light scatter compared to Plossls and orthoscopics but the differences were never enough to count. i.e. There was never an occasion where I could not see a tight companion in one over the other at comparable magnifications. Indeed, the HR series of eyepieces have very restrictive fields (42 degrees), even compared with the modest 50 degree fields offered up by a Plossl and/or the Baader classics (which have a larger 50 degree field) when Barlowed allow for significantly larger fields to be exploited. There is thus a distinct advantage to the using the far less expensive Plossl and orthoscopic type eyepieces over the HR series (the three of which will set the consumer back a hefty £750 UK), especially when employing a non-motorised altazimuth mount such as my Vixen Porta II.

Don’t believe the hype; binary stars are very simple, just tight little Airy disks. Save your money and use it more productively on other things.

Well, I hope you enjoyed this blog and that you don’t become discouraged observing throughout the twilight season wherever you live.

Thanks for reading.

 

Neil English’s new book, Tales from the Golden Age, uses history to debunk a few myths that have crept into modern amateur astronomy. Available in late 2018.