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

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

 

What’s in a name?

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

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

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

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

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

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

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

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

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

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

Looking down at the ocular lenses. Note the specifications.

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

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

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

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

 

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

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

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

Optical Testing

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

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

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

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

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

Spiffing good.

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

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

Full specifications of the instrument here.

 

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

 

De Fideli.

 

 

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

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

 

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

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

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

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

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

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

The 10 x50 Sierra binocular in its soft carry case.

 

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

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

 

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

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

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

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

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

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

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

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

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

 

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

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

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

Ad Astra

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

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

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

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

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

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

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

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

Some other daylight tests:

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

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

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

 

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

Attaining binocular stability without sacrificing mobility

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

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

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

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

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

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

 

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

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

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

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

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

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

November 17 2018:

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

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

 

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

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

 

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

Simplicity itself.

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

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

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

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

Final testing: November 18-20 2018

Guid graith.

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

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

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

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

Thanks for reading.

 

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

 

De Fideli.

A Visual Extravaganza Under Dark Scottish Skies.

Looking east: sunrise over Wigtownshire.

 

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

                                                                              Psalm 19:1

 

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

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

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

 

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

The shores of Loch Ken, near Castle Douglas.

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

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

 

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

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

 

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

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

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

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

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

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

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

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

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

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

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

 

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

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

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

A little achromatic pair.

 

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

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

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

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

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

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

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

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

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

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

 

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

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

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

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

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

An old friend: Theta Aurigae.

 

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

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Concluding Comments:

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

 

It was good to get away.

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

We will certainly be visiting again!

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

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

Fair is fair I suppose lol!

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

 

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

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

 

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

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

So dV = 4πr^2dr.

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

N = 4nπr^2dr.

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

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

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

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

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

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

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

You can’t have an uncaused cause!

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

 

In the beginning God created the heavens and the earth.

Genesis 1:1

 

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

Zechariah 12:1

 

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

 

De Fideli.

The Venerable ShortTube 80 Refractor.

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

 

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

 

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

 

De Fideli.

Using Small Newtonians in a Terrestrial Setting.

Snug as a bug in a rug, ken.

 

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

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

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

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

Product 1: SkyWatcher 10mm Erecting Eyepiece

The SkyWatcher 10mm Erecting Eyepiece.

 

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

The coated eye lens of the SkyWatcher erecting eyepiece.

The field lens has no anti-reflection coatings.

 

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

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

Product 2: Roof-prism based image rectifiers

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

The Angeleyes and Datyson image rectifiers.

 

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

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

 

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

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

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

 

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

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

Product 3: The Vixen Terrestrial Image Adapter

Schmokin; the Vixen terrestrial image adapter.

 

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

The top lens showing anti-reflection blooming.

The bottom lens showing blooming from anti-reflection coatings.

 

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

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

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

 

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

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

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

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

Notes on field use:

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

Independent verification of these findings

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

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

Source here.

Comparison with conventional spotting telescopes

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

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

                                              Newtonian                                                       Refractor

Aperture                               130mm                                                              100mm

Resolving power                   0.89″                                                                 1.14″

Colour correction               Fully apochromatic                                 Pseudo apochromatic

Twilight  factor                               58                                                               46.9

Field of view (max)                     1.5 degrees                                               1.9 degrees

Magnification range                      26-300+                                                        22-67x

Close focus distance                      20-25 yards                                                  25 yards

Length                                              23.5″                                                                 20″

Weight:                                           3.8 kg                                                              2.52kg

Cost:                                             ~£350                                                                £1,180

Interchangeable eyepiece           yes                                                                   no

 

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

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

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

Moral of story: Improvements are costly!

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

 

Postscriptum:October 23 2018

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

Thank you for reading!

 

De Fideli.

Product Review: The Barr & Stroud 8 x 42 Sierra Roof Prism Binocular

The Barr & Stroud 8 x 42 roof prism binocular.

 

With some sage commentary from former Sky & Telescope columnist, Gary Seronik.

Binoculars are indispensable tools for the naturalist and amateur astronomer. Their strength lies in their ease of use, low-power, wide-field views of the Creation, whether terrestrial or celestial. In this era of high technology, there is a huge number of models to suit just about everyone’s needs, wants and budgets. Content with my old 7 x 50 porro prism binos for three decades, I came to realise recently that it would be good to get a newer model that was better suited to my life circumstances.

I had grown older you see, with the result that the maximum diameter of my pupil could no longer open to 7mm. I became less tolerant of the fairly substantial weight of the 7 x 50s too, especially when I took some time out to relax on a recliner in my garden to gaze upon the heavens for prolonged periods of time. The 7 x 50s also suffered some knocks over the years and once they were fully submerged when I accidently slipped on some moss and fell into Loch Lomond lol. Luckily, though a source of considerable hilarity to my travelling companions, the ordeal wasn’t the end of the world, and though the prisms became mis-aligned, I managed to get them repaired at reasonable cost.

But what really catalysed my desire for a new binocular was the recent acquisition of an inexpensive 10 x 50 binocular I received in a swap (barter) for an eyepiece with a fellow amateur. At first I was thrilled with the 10 x 50s. They had a suitable exit pupil (calculated by dividing the diameter of the objective by the  magnification), but they were quite heavy and owing to their ‘fully coated’ specifications, manifested significant light loss and reduced contrast owing to the presence of internal reflections when pointed at a bright light source.

I knew what I wanted going foward though. The binocular needed to be light weight but not feather-weight, as my experience with small compacts were somewhat less than inspiring. Somewhere between 600 and 700g would be ideal. The instrument had to be fully muti-coated to reduce light scattering inside to an absolute minimum. I could dispense with ED glass, as at the magnifications I intended to use the binocular at, I would be very hard pressed to see any secondary spectrum and I wasn’t going to splash out on an optical feature I could’t readily see! Much more important for me was that the binocular be well made and have a secure, rugged feel to them in field use.

I considered field of view too; at least 7 angular degrees but not overly wide since I reasoned that although some models were being offered with impressively wide fields up to 8 angular degrees or more, they would likely suffer more from off-axis aberrations that I would notice in field use.

Many of the ‘premium’ models also had features that I could readily do without as well: a slightly flatter field at the edge of the field, for example, or faster, smoother focusing that might be somewhat more important for observing fast moving wildlife at close hand; or a lockable diopter setting; those kinds of things.

Waterproofing would be a bonus, for sure, but not essential, as I don’t spend my days wading through swamps in search of feathered friends lol!

I decided that a full-size 8 x 42 roof prism binocular was the way to go. I was delighted to see that even very highly respected brands were offering many of the attributes I wanted without ED glass elements. For example, here’s one Fujinon model I considered. If Fujinon of Japan did not consider ED glass as an essential feature in a modern binocular, then why should I?

Consulting former Sky & Telescope columnist, Gary Seronik’s beautifully illustrated book, Binocular Highlights (Second Edition 2017), I was able to affirm what I felt about the view served up by a premium optic compared with mid-priced models:

….You can get good optics for relatively little money. So what do you get if you spend ten times as much? In terms of the actual view, not as much as you might expect. Yes, the more expensive binoculars have better optics that will deliver more light to your eyes and sharper images, but the difference is not night and day. What the extra money does buy is mechanical quality. Expensive binoculars can withstand the inevitable bumps and knocks of everyday use without trouble, and having focusing mechanisms that are sure and precise.

pp 11

 

Being new to this type of binocular, I did however find out the hard way that not all roof prism binos were created equal. My first purchase was a model that did have everything I was looking for, save for phase-coating technology which corrects for the inherent design flaw in all roof-prism binoculars. Finally, I purchased a model that did tick all my boxes; enter the Barr & Stroud Sierra 8 x 42.

It’s specifications can be viewed here.

The Sierra 8 x 42 came well packaged inside a handsome box. As well as the binocular, I received a lens cloth, neck strap, soft, padded carry case, a single-page instruction sheet and a warranty card (10 years).

Right from the get-go, I was very impressed with the fit and feel of the binocular. The fern-green body is fashioned from polycarbonate with a rubberised overcoat. The central bridge was set at just the right degree of stiffness, ensuring that when I adjusted the inter-pupillary distance, it was rigid enough to stay snugly in place; so no need for constant re-adjustment when taking them from their case. Both the objective and ocular lenses had good rubber-like caps that can be affixed to the binocular with a much reduced chance of getting lost while on the move.

The Barr & Stroud Sierra come with nicely made, stay-on rubber caps for both the ocular and objective lenses. Very handy both in the field and during storage.

 

Both the objective and ocular lenses have lovely anti-reflection coatings that make the lenses all but disappear when looking straight through them.

The great anti-reflection coatings on the achromatic objectives of the Barr & Stroud Sierra.

 

The Sierra come with adjustable eyecups that click up or down for use with or without  eye-glasses. With its generous 17.8mm eye relief, eye-glass wearers will be able to enjoy the full field of view by keeping the eyecups in the fully down position. I do not use eye-glasses when observing, so I always have the eyecups twisted fully upwards.

The twist-up eyecups ‘click’ into place for comfortable viewing of the entire field for use with or without eye-glasses.

 

The diopter setting is located under the right eyecup. It is satisfyingly stiff and, as a result, fairly difficult to adjust. I thought this was plenty good enough for my use, as it has not budged a millimetre since I made the adjustment for my own eyes on the day they were acquired!

The diopter ring is located under the right-hand eyecup and is very stiff and difficult to move out of position while in field use.

 

As the specifications reveal, the instrument is nitrogen purged and o-ringed sealed making it fog and water-proof. Since molecular nitrogen [consonant with the name ‘azote’, (meaning ‘without activity’) bestowed upon it by early chemists] is quite an inert gas, it also ensures no moisture- or oxygen-induced corrosion will occur to its internal components for the foreseeable future. Argon gas filling would have been better, of course, since it is even more inert (being a Noble element) than nitrogen and its larger atomic mass would ensure even more sluggish diffusion-based leakage over the years. But for my purposes though, ordinary nitrogen was deemed perfectly acceptable. The specs also say the instruments have been immersion tested and can withstand being submerged in up to 1.5 metres of water for 3 minutes; that’s plenty of time to retrieve them if ever an accident should occur!

I’ll not be testing that by the way, lol!

    Optical Testing & Handling in the Field

It does exactly what it says on the tin!

 

The Sierra 8 x 42 provide instant gratification from the moment you pick it up. It feels very secure in the hand. The view is very clear and sharp and colour rendition sensibly perfect. The factory collimation was spot on. The focus wheel is very responsive and smooth allowing you to zoom in on a subject as close as 6.5 feet all the way out to infinity. If you look carefully at the edges of the field, there is some softening of the image as well as a trace of chromatic aberration but not enough to distract the vast majority of users. Examining a horizontal roof at 30 yards distance revealed very little pincushion distortion.

Comparing it to my old 7 x 50s revealed something rather shocking; the image was actually brighter and sharper in the Sierra, despite it having smaller objective lenses ( 42mm as opposed to 50mm). I attribute this to solid advances in the application of better coatings to all optical components and superior baffling of stray light in the roof prism binocular. Focusing on the middle distance, the binocular provides very impressive depth of field perception but maybe not quite as good as that provided by their porro prism-based counterparts.

Definition of daytime targets is excellent. It presents autumn leaves in their beautiful colours and focusing in on tree trunks showed up its wonderful textured grain. I can easily carry them round my neck for many miles and with little in the way of neck strain. The binocular can also be attached to a tripod if need be using the 1/4-20 threaded socket found under the B&S logo at the front of the bridge. Just unscrew the plastic cover and screw in the tripod adapter.

As a rather severe test of how well stray light is managed in the binocular, I pointed it at the full Moon. The inexpensive 10 x 50s showed clear evidence of internal reflections producing annoying glare in the image and thereby reducing contrast. To my relief, the Sierra 8 x 42 showed very little in comparison indicating that stray light was being very well controlled.

A week after full Moon, I examined a rising last quarter Luna and again, the image was very impressive; there being very little glare and contrast remaining very high. The only false colour I could see was attributed to atmospheric refraction. The battered southern hemisphere with its vast crater fields stood out well, as did the contrast between the brighter and darker maria. I particularly enjoyed seeing the wonderful earthshine from the dark hemisphere of the Moon which made the view all the more magical.

Continuing my adventures with the Sierra under the stars, the binocular has a wide field of view (7.33 degrees), allowing you to take in generous swathes of sky. Stars focused down to tiny pinpoints across the vast majority of the field, with only the edges of the field showing a slight softening and the merest trace of lateral colour. I judged the contrast to be very good.

Confident that I had indeed obtained a very good binocular, I relaxed and just enjoyed the magnificent views it served up of large deep sky objects; the Hydaes was wonderful and filled the view with lots of room to spare, the Alpha Persei Association was spell-binding with many dozens of hot, white stars assaulting my eyes. The Pleiades was a beatufiful sight to behold. Bright stars such as Aldebaran, Capella and Vega faithfully revealed their true colours (orange, yellow and blue-white, respectively).Running the binocular through the Milky Way in Cygnus and Cassiopeia was a joyous experience and proved quite overwhelming to this tester.

The Sierra 8 x 42 will be an excellent new tool in my arsenal of optical instruments. It will complement the detailed, close-up views served up by my telescopes. The binocular will be accompanying us on our up-and-coming family vacation to the Solway Firth in southwest Scotland next week (commencing Monday October 15 2018) together with my 130mm f/5 Newtonian travel ‘scope.

The perfect binocular accompaniment.

 

I heartily recommend this binocular to amateur astronomers, nature watchers, for those who love poking around the landscape, or as the perfect optical accompaniment for a day at the races. It will offer up very satisfying performance at a price that won’t break the bank. It provides excellent value for money and, if properly cared for, provide a lifetime of wonderful views.

Postscriptum:

Please check out some other reviews of Barr & Stroud Binoculars:

The Barr & Stroud Sierra 10 x 42 Sierra

The Barr & Stroud 8 x 32 Sierra

The Barr & Stroud Savannah 8 x 42

 

Neil English’s new book, Chronicling the Golden Age of Astronomy, explores  four centuries of visual telescopic astronomy, as well as the pantheon of colourful characters who helped shape both the hobby and the science today.

 

De Fideli.

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.

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.