De Rerum Natura

Hubble deep Field Image. Credit: Wiki Commons.


However, the Most High does not dwell in temples made with hands, as the prophet says:

 ‘Heaven is My throne,
And earth is My footstool.
What house will you build for Me? says the Lord,
Or what is the place of My rest?
Has My hand not made all these things?’

                                                                                         Acts 7:48-50


A new paper by a team of Oxford University scientists, submitted to the Royal Society, London:

Dissolving the Fermi Paradox

(Submitted on 6 Jun 2018)

The Fermi paradox is the conflict between an expectation of a high {\em ex ante} probability of intelligent life elsewhere in the universe and the apparently lifeless universe we in fact observe. The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation, which suggest that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty regarding highly uncertain parameters. We examine these parameters, incorporating models of chemical and genetic transitions on paths to the origin of life, and show that extant scientific knowledge corresponds to uncertainties that span multiple orders of magnitude. This makes a stark difference. When the model is recast to represent realistic distributions of uncertainty, we find a substantial {\em ex ante} probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it. This result dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe.

Full Paper here



De Fideli.

The “Foot” ‘Scope Project: Part II

Foot sized powerhouse; the author’s 12″ f/5 Newtonian.

















April 13 2018

In a previous communication, I described my acquisition of a Revelation 12″ f/5 Dobsonian telescope, which delivered fine images of selected double stars and which was used to establish the Taylor hypothesis, namely, that if the seeing conditions are fair to average or better, sub–arc second pairs can be readily observed at appropriately high magnifications using the generous aperture of this telescope.

After conducting this body of work, I have had little time to enjoy the considerable benefits of observing with a big Newtonian system such as this, but in this blog I hope to report still more observations with the same telescope and improve its optical and thermal  performance in the field.

During the course of that previous communication, I described the optics in this telescope as being unreasonably good. Indeed, they far exceeded my expectations given the very modest cost of the telescope! I also described some modifications I made to the instrument, including the re–coating of the secondary mirror (just 70mm semi major diameter giving a 23 per cent central obstruction) with super–high (97 per cent) reflectivity coatings as well as the procuring of Bob’s Knob’s  to assist precise collimation in the field, but I postponed some other aspects of this project. In particular, I wished to also have the coatings on the large primary mirror similarly upgraded in order that it would increase light throughput to the eye as well as improving the overall contrast of the images so rendered.

Today, I endeavoured to resume work on the telescope and that meant removing the primary mirror from its cell in order that I could despatch it to the mirror coaters located south of the border in England. The mirrors for this telescope were sourced from GSO and seem to have been more or less consistently good, as judged by other experienced amateurs who had taken the time to assess one or more units of the same product. One such assessment is documented here and I would heartily agree with the conclusions of Mr. Stoitsis.

After removing the mirror cell from the rear of the optical tube, I was able to accurately measure its thickness, as well as assess the design of the accompanying cell. The thickness of the mirror was measured to be 36mm (so 1.5 inches), yielding a mirror thickness to aperture ratio of 1:8. This result is consistent with this author’s finding in respect of the ability of the telescope to acclimate adequately to ambient outdoor temperatures, allowing him to make those important observations with regard to resolving sub–arc second pairs.


The 30cm aperture GSO primary has a thickness of 36mm (1.5 inches).

















The mirror cell is housed in an open cell. It appears to be well designed and incorporates a 9–point floatation system; just about perfect for a mirror with these dimensions.

The 9–point floatation system of the 30cm aperture GSO primary mirror cell.

















The mirror was then carefully packed away for safe passage to the mirror coaters.

Packaging up the primary for re–coating.

















I hope to despatch the mirror early next week, so hopefully I will have it back in a few weeks; just in time to explore the deep sky glories of spring!


April 14 2018

Time: 23:20UT

Almost forgot to tell you: several weeks after exchanging resources for the foot ‘scope, I received an envelope in the post. Curiously, I prized it open, and there it was! A small, battery powered fan; the same one that originally came with the telescope! As I explained in the opening blog, I wasn’t too bothered about not having it, nor did I really need it. But it was a warm gesture from the original owner of the telescope to send it on; something I appreciated!

The little fan.

















Time: 4:20 pm

As described in previous blogs, I also wish to line the inside of the 1450mm long tube with cork and overlay this with flocking material. Materials were ordered yesterday and should keep me busy until the primary returns home.

April 21 2018

Time: 5:45pm

Lining the 12 inch optical tube assembly with cork.

















With a decent spell of settled weather now upon us, I spent the afternoon lining the inside of the optical tube with a thin layer of cork. The product I chose has an adhesive layer on the underside of the cork substrate and adheres to the rolled aluminium tube fairly easily. The cork itself is very delicate though, and so some care must be taken not to tear it while preparing the strips. 3 full 100 x 45 cm rolls were used up today, but I needed to order up a couple of extra rolls to complete the job. These arrive on Monday so I can complete the task then. The flocking material has already arrived so that will be overlaid on the cork. This afternoon, I only flocked the inside of the focuser draw tube.

The mirror arrived safely at the coaters and on the invoice they noted its diameter to be 303mm. Hoping to have it back in a week or so.

Date: April 24 2018

Time: 3:10pm

The tube now fully insulated and flocked.

















Well, I finally managed to complete the cork lining as well as covering it over with flocking material. Since the rolls are the same size ( i.e. 45 x 100cm), I can report that it will take 4 complete rolls of each material to insulate and flock the optical tube assembly of the 30.3cm F/5 Newtonian. I’m pleased with the result. All I need do now is wait for the arrival of the primary mirror and I’m back in business.

Date: May 8 2018

Well, the primary arrived back safely from the coaters this morning. I was busy with a few other things so only did a quick check to see that all was well. It was exceptionally well packed for transit. Later on, I gave it a good look over and can say that the firm did another excellent job applying the high reflectivity coating to the 30.3cm mirror, and they centre spotted it, as requested.

The recoated 12 inch primary mirror arrives back home in perfect nick.













Side view.

















It was then carefully placed back inside its cell, making extra sure that the clips holding it in place were not overly tightened to avoid pinching of the optics.

Mirror now back in its cell for remounting onto the optical tube.

















After putting the mirror back inside the tube, I left it outside to cool in the bright evening sunshine.

The innards of the foot ‘scope.
















Following a few hours of rain, it cleared up in the late afternoon and stayed that way well into the evening. So, all I need to do is align the optical train before sunset and I can take it for a spin under the stars.

Awaiting darkness in a race against time.

















Date: May 9 2018

Time: 00:00UT

What a glorious night! Telescope performed flawlessly!

Boys oh Boys!

Will tell you about it later today.

Starting at about 11:30pm local time, as the twilight had all but abated, the fully acclimated and carefully collimated telescope rendered excellent star tests on a few third magnitude stars, with a very high degree of symmetry in the intra- and extra-focal images at 250x. I could however detect a trace of under-correction, as I reported before, but it was not enough to bother the image in any significant way. In focus, the same stellar targets rendered hard, round Airy disks with no astigmatism or coma at the centre of the field at powers up to 450x (the highest tested this evening). No evidence of pinched optics was manifest.

My first proper target was Izar(Epsilon Bootis) now sitauted high up the southeast. At 250x, the image was remarkable! Both the primary and the secondary were beautifully resolved and intensely bright! Bright targets like this would actually benefit from filtering in this large telescope with a neutral density filter or polariser. As the sky darkened further, I turned the telescope on two stellar targets with very faint companions in comparison to their primaries. Keeping the magnification at 250x, Polaris B stood out wonderfully well; far more ‘in your face’ than the images garnered by even the 8 inch f/6 Newtonian. Even more striking was the very faint and close-in companion to Alula Borealis. The ruddy primary here shines at magnitude +3.5, and the secondary, a feeble +10.1. The 12 inch cleanly resolved the pair separated by about 7.4″ of dark sky, with the companion very obvious and much more easily seen than with any of my smaller telescopes. Where even the 8 inch requires some degree of concentration to pick off the secondary, the 12 inch made it very easy to see at a glance. Indeed, I can’t recall seeing it so well and so easily!

As the sky became maximally dark between midnight and 1 am local time, I turned my attention to a variety of deep sky objects to assess both the light gathering and defining power of the 12″ f/5. And here again, I was not disappointed!

I first turned the telescope on M 51 in Canes Venatici, now very well placed high overhead. Even with the 32mm Plossl I used to centre the galaxy in the field, it was strikingly bright and obvious in the expansive, low power portal. Inserting my 7.5mm Park Gold ocular delivering 200x, I was able to discern far more of the spiral structural details in the galaxy’s spiral arms of this amazing target. Indeed, it was in a completely different league to the views I have recently been enjoying with my 8″ f/6 Newtonian. A very enjoyable experience!

Next, I moved into Hercules, which by this time was well placed high in the eastern sky. Excitedly, I turned the 12″ on its deep sky jewel; Messier 13, the great globular cluster some 23,000 light years away. The instrument served up an amazing image at 200x( 7.5mm Parks Gold), but it was even better at 250x (6mm Baader ortho). The storm of stars resolved in this large aperture telescope was simpy mesmerising and again in a completely different league to that rendered in any of my smaller instruments. For kicks, I cranked up the power to 450x (Parks Gold 7.5mm with a 2.25x Baader shorty Barlow), refocused and sat back to enjoy a field of view littered with innumerable faint, round stars, all finely resolved right down to the core. Lesser instruments just run out of light at these very high powers but not so with the 12″!

Not too far away and significantly higher up in the sky was Messier 92, and once the telescope was centred on it, it produced a wonderfully sharp and well resolved globular cluster, with many hundreds of individual stars clearly seen at 250x (Baader 6mm ortho). As before, while the view in my 8″ f/6  was rewarding, the 12 inch takes you to a whole new level of visual experience!

My final targets were located in Lyra, which I visted shortly before 1am local time. First I turned the telescope on the famous Double Double (Epsilon 1 & 2 Lyrae). At 250x, all four components were beautifully resolved and intensely bright, more like distant coach lamps etched onto the sky than anything else. Slightly lower in altitude was M57, the famous Ring Nebula. At 250x, the image of this planetary nebula, more like a luminous smoke ring, was big and bright and easy to study. Generous amounts of structure were delineated at 450x along its southern border, with many gradations of brightness, mottling etc observed in the brighter outer annulus. Central star not seen (of course!) but many more stars observed in its immediate hinterland than that presented in the 8 inch instrument.

Conclusions: The telescope delivered great images, fully in keeping with its large, high quality optics. I am adequately convinced that the 12″ gains that extra (approximately) one magnitude over the 8 inch telescope, allowing many deep sky objects and faint stellar companions to be more easily studied.  Throughout last night’s vigil, the stellar images at very powers remained tight and calm, suggesting that the insulating cork lining was doing its job (no fan used). All images were presented with very good contrast and with little in the way of stray light drowning out the faintest details. If anything, the experience in the field induced strong desires for even more aperture. But it is reassuring to realise that in order to gain yet another magnitude in light grasp, I’d have to move up to an 18 inch!

I am over the Moon with the performance of this telescope, which was purchased for just a few hundred pounds. And even with the additional costs of the modifications, the overall financial outlay came in at about half the price of my most expensive telescope; a diminutive but very fine 5″ f/12 refractor. Heck, that telescope would make a good finder on the 12 inch behemoth lol.

Date: May 10 2018

Time: 20:15 UT

The foot ‘scope passively cooling.

















The forecast looks good again this evening and so I can spend more time with the foot ‘scope. I leave it set up in my back garden with the optics capped and let it cool naturally to ambient temperature for a couple of hours before commencing observations. That way I can return to my writing committments and/or other things. Although one can have the instrument set up permanently in a cool outhouse, I want the coatings I invested in to last as long as possible. Water vapour and its condensations are the enemies of all optical coatings, so that’s why I store all of my Newtonians indoors when not in active use. My Newtonians are all long term committments; parts of my family, as it were. And like everything else that is valuable in life, it pays to give your instruments a bit of TLC if they are to deliver top perfomance time and time again.

Date: May 11 2018

Time: 23:00 to 00:30 UT

I enjoyed another hour or so of good dark skies last night, visiting a whole suite of double stars in Coma Berenices and Bootes, which were well placed near the meridian at this time. Conditions were a little hazier this evening though, reducing transparency.

There are two lovely doubles in Coma worth visiting; 24 Com, which consists of a gorgeous colour contrast double, the primary shines with a ruddy complexion at magnitude 5 while the ‘secondary’ has a gorgeous blue white hue some 1.3 magnitudes fainter. The system is orientated roughly east to west and very nicely framed at 200x.  I say ‘secondary’ as it is unknown whether this is a true binary system and at this time, the consensus appears that they are unrelated. The second system visited was 35 Coma, with the telescope easily resolving this tight duo of yellow and yellow white components with a striking 9th magnitude outlier. I believe this system is a little over 1 arc second at the present time but is slowly converging over the next few decades. A power of 450x was found to be optimal to splice this puppy, the components of which are 5.1 and 7.1. The orbital period of this system is about three and a half centuries.

Then into Bootes; Iota, Epsilon,Kappa, Mu, Pi  and Xi were beautifully rendered at 200x to 250x. With the generous aperture of this telescope, the stellar members of these systems were very brilliant and colour faithful. Seeing was not as good last night as on the previous night, but I was extremely impressed at how the instrument maintained high quality images over periods of a few minutes, as each system in turn was studied at leisure.

Yet again, I was very impressed with the optical prowess of this large telescope. It holds collimation well (I checked it at various times and in various orientations throughout the vigil), perhaps a tad better than my other Newtonians. It also appears to be behaving itself thermally, which is a great relief. Again, no active cooling was employed.

As I was packing up my gear, I realised that I had not named this telescope properly. I can’t just call it the ‘foot ‘scope’ forever now can I?  But what shall I call it?  Not ‘Alexa’ to be sure; far too creepy for my liking. I need to spend more time with the instrument before I decide.

Time: 13:15 UT

A quality focuser.

















I am thoroughly enjoying the sturdy dual speed focuser on the 12″ f/5. All my other Newtonians have simple, singe speed focusers but having the ability to very finely adjust the focus position during high power applications is a great bonus. Frankly I’m amazed that the manufacturers were able to offer this feature as standard equipment with the telescope. A super nice touch!

Well, though the morning was quite cloudy, with the rain arrving on schedule this afternoon, the forecast says that it will quickly pass through, leaving the evening clear once again. I would like to return to the realm of the globular clusters; but not in Hercules. There can’t be many dark nights left what with summer twilight knocking on the door.

Time: 23:00UT

The sky has not yet cleared up. Up early tomorrow so need to call it a night anyway.

Date: May 14 2018.

Time: 23:00 UT


The light bucket.

















After a cloudy and wet morning, the skies cleared to give a beautiful sunny afternoon. Those conditions gave way to a good clear night, but even at midnight local time, the twilight has noticeably brightened in the last few days, especially towards the north. I set the foot ‘scope out about 10pm local time to fully acclimate prior to resuming observations. Tonight I wish to begin with another celebrated globular cluster, Messier 3, conveniently located almost exactly half way between Arcturus and Cor Caroli.

Time: 00:15UT

Another great night, although the seeing was a bit rough. Nonetheless, some great sights captured in the foot ‘scope. Will tell you about what I got up to later today. Nite nite.

Starting about local midnight, I trained the 12 inch Dob on Messier 3 in Canes Venatici. Centring the object in the low power (47x), approximately 1 degree field of my 32mm SkyWatcher Plossl, I noted a fairly bright field star just west of M3 which provided a means to carefully focus the image. Messier 3 has a very condensed core with quite a few stars being resolved at its periphery. Both my 5.1″ and 8″ Newtonians are well able to resolve the outer parts of this globular cluster but the core remains stubbornly unresolved even at higher powers. Not so with the 12″ instrument, which opened up this globular at powers of 200x and 250x, showing many more stars resolved to its core. The instrument works well with simple, short focal length eyepieces. Indeed, my 4mm Revelation Plossl, which delivers a power of 375x, produced a truly wonderful view, where its constituent stars filled the 0.14 degree field of view. Tracking the instrument was never a problem owing to the smooth azimuth and altitude bearings on the Lazy Susan mount, which enables me to nudge the telescope along as the object drifts through the field from east to west.

M 3 is noticeably smaller than M 13. But it is also located some 10,000 light years further away from the solar system than the latter, explaining its smaller angular size at equivalent magnifications.

This telescope is worth every penny spent on it just for the quality of the views of globular clusters alone. The foot ‘scope is a veritable “glob buster.”

I recorded 4 bright telescopic meteors during my 75 minute vigil.

Keen to get a look at some other showpieces before the worst of the twilight returns, I turned the telescope on the bright galaxy pair, Messier 81 & 82 in Ursa Major, and my trusty 32mm Plossl framed both galaxies in the same field of view. Even at this low power, the generous light gathering power and resolution of the telescope displayed these galaxies extraordinarily well, with prominent mottling in M82 evident at a glance along its major axis. Cranking up the power to 200x using my 7.5mm Parks Gold, clear spiral structure in M81 could be made out without much effort. Again, the level of detail seen in these galaxies is a very significant increase over my next most powerful telescope; the 8″ f/6 Newtonian.

Time: 21:15 UT

Another clear night beckons, so more tests can be made on the foot ‘scope.

Date: May 15 2018

Time: 00:20 UT

Tonight I enjoyed a stellar extravaganza, cruising at 200x through a wilderness of light and colour. More info later today.

Last night’s spell with the telescope took me to a variety of colour contrast double stars. First came 30 and 31 Cygni, arguably one of the most comely binocular doubles in the entire sky, the brilliancy of the stars and their colours; orange and turquoise were beautifully framed in the 0.25 degree field of my 7.5mm Parks Gold eyepiece delivering 200x (a rather pedestrian magnification for this large telescope). While smaller ‘scopes certainly present this vista well, the view is truly transformational in this large aperture telescope owing to its superior light grasp and defining power. I then moved south to Beta Cygni (Albireo) and enjoyed a wonderful view of the marmalade orange primary and blue –green secondary at the same power. It was just a joy to see them so faithfully rendered in their true colours and shining so intensely in the telescope.

Following this, I ventured into the large and sprawling constellation of Hercules, starting with Rasalgethi(Alpha Herculis) with its red giant primary and bluish companion perfectly framed in the eyepiece. Then I threw caution to the wind and moved higher up the sky visting each star brighter than 5th magnitude within the constellation, examining their hinterland in the 200x portal. As I moved from star to star using the 8 x 50mm finder, I was amazed at the sheer light gathering power of this telescope and the number of extremely faint stellar ‘companions’ which attended many of the brighter stars. Where my smaller telescopes only revealed the brighter members or none at all, the 12″ f/5 pulled in many more! I was reminded of the work of the English amateur astronomer, the Reverend T.H.E.C Espin of Tow Law, Northumbria, who used a 17.25 inch equatorially mounted Calver reflector at the turn of the 19th century to discover a sizeable tally of these faint and wide companions strewn all across the northern sky. It seems that good reflecting telescopes are ideally suited for such work. Indeed, they can hardly be beaten in these pursuits!

With every increase in magnitude, there is a corresponding increase in stellar number, but there is no fixed power law that might enable us to compute how many more stars there might be as the magnitude is increased. The distinguished 19th century German astronomer, F. W. Argelander, estimated that each magnitude exhibits a rise of about 300 per cent. Indeed, in data presented on page 294 of W.F. Denning’s masterful tome, Telescopic Work for Starlight Evenings (1891), he provides these figures, collated from a survey between 2 degrees south of the equator all the way to the north pole:


1st: 20


2nd: 65


3rd: 190


4th: 425


5th: 1100


6th: 3200


7th: 13,000

Having spent some time traversing the stars of Hercules, I can definitely see that Denning was on the right track. Indeed, I would say that the 12 inch instrument does yield an approximately three fold (maybe more) increase in star numbers over my optically excellent 8 inch f/6 Newtonian; and in many cases that is sufficient to change the visual perspective of each telescopic field by a considerable degree. In small telescopes, many star fields can present as rather bland and uninteresting. Patently not so with the 12″ f/5!

Although the sky is clearing up as I speak, I have decided to take a break tonight as I’m knackered and need to recharge the ‘batteries’. More to come soon.

Date: May 16 2018

Time: 18:00UT

I love the low tech approach of the Dobsonian. No electronics to fiddle with, no star alignments to perform. Just mount it on its lazy suzan and you’re off to the races. But this simple approach doesn’t suit everyone. In particular, many prefer driven mounts that keep objects centred in the field while making observations. If that’s your forte then there’s a solution; enter the driven Dob mount. Many such equatorial platforms are available for purchase today and they vary quite a bit in price, but these days you don’t have to spend a fortune acquiring one. Have a look at this one, for example. All you need to do is adjust the inclination of the platform to coincide with your latitude(in my case it’s 56 degrees North), power it up and you can enjoy an hour of active tracking before you have to reset it. If you do decide on one, you need to ensure it can be adjusted to your latitude angle. That’s why a variety of them can be purchased to suit your precise location, either south or north of the equator.

The good Lord has granted us a spell of settled weather here and tonight looks very good to go. Where will my foot ‘scope carry me off to this evening?

Date: May 17 2018

Time: 00:30UT

The Wide field experience.

















Tonight I stuck mainly to low power, wide–field viewing. When coupled to a good 2 inch wide–angle eyepiece, the foot ‘scope serves up some spectacular views! More later.

Time: 20:00UT

Last night the foot ‘scope did experience some thermal issues as it struggled to follow the rather large temperature differential between daytime highs and night time lows. This time of year, we tend to experience larger temperature swings than in other months where it is not especially unusual for the diurnal temperature variation to exceed 15C (as opposed to about 5 or 6 degrees which is normal). As a result, high magnification images of stars were quite swollen and, in the absence of any breeze,  I considered using the battery–powered fan. In the end, I changed strategy and decided to explore the wide field sky around Lyra and Cygnus.

Beast of an eyepiece: the Explore Scientific Maxvision 40mm wide angle ocular.

















The telescope came with two eyepieces from the former owner; a Revelation 30mm 70 degree Superview 2 inch ocular, as well as a 9mm Revelation Plossl. The former unit was quickly found to be adequate on axis but rather poor off axis, with coma, distortion and astigmatism being in evidence. To enjoy a much more immersive view, one needs to invest in a higher quality wide angle ocular. The 32mm Plossl gives a significantly smaller true field but off axis aberrations are still manifest. To this end, I removed the 1.25″ adapter on the focuser and reached for my 40mm Explore Scientific Maxvision 68 degree eyepiece, which has been used extensively over the last few years with my 8 inch f/6 Newtonian.

While the exit pupil was pushing 8mm on the 12″ f/5, I was delighted with how well it performed. Yes, there was some minor light loss but otherwise it served up excellent, bright and sharp images of star fields out to about 90 per cent of the way to the field stop. And even then, the distortions were more than tolerable. The Maxvision eyepieces are clones of the longer established Meade Super Wide Angle(SWA) and Tele Vue Panoptic oculars, but are offered at significantly lower prices.

To best match the faster f/5 system of the foot ‘scope with my 49–year–old eyes, I ordered up the 34mm unit, which will deliver an excellent 1.5 degree true field, a magnification of 44x and sub–7mm exit pupil. This will be an excellent eyepiece for sweeping the heavens for comets, faint nebulae and open clusters on the precipice of visibility. A large, high–quality telescope like this deserves a good, wide angle eyepiece. The Maxvision range offer this quality at very attractive price points (£114 plus postage). I’m hoping to receive the unit by the middle or end of next week. Of course, there are other options for money conscious amateurs; the second hand market is likely to have something suitable come up from time to time and with patience and discernment, good deals can be had.

This evening looks good to go again, but I would like to take a break from the foot ‘scope for a few days and feed some starlight to my smaller instruments. More soon.

Date: May 18 2018

Moon watching.

















Time: 21:30UT

Last night I enjoyed a wonderful evening of double star observing with my 130mm f/5 Newtonian.The sky was very tranquil, allowing almost textbook perfect images to be generated on a variety of systems. The good weather remains with us again today and this evening I noticed a beautiful crescent Moon hanging in the western sky. I just couldn’t resist the chance to observe it in the 12″ f/5. My 32mm SkyWatcher Plossl delivered a jaw dropping view of the crescent at 47x in a one degree field and the wondrous earthshine enveloping its darkside. Reaching for my 7.5mm Parks Gold delivering 200x, I was delighted with the razor sharp views of the lunar regolith, especially considering its fairly low altitude at the time of observation. Though not a lunar observer per se, I look forward to observing this magnificent world with the foot ‘scope as it rises higher in the sky in the coming days.

Date: May 21 2018

The new 34mm 68 degree Maxvision eyepiece arrives tomorrow, so not as long a wait as I anticipated.

Date: May 22 2018

Time: 21:30UT

The foot ‘scope fighting the Spring haar.

















I set the foot ‘scope out late this evening so that I could get a quick look at a fairly well placed first quarter Moon, with the express intention of testing the high magnification images garnered by the telescope. In the end, it proved an exercise in frustration more than anything else, as the haar (low altitude cloud and mist) came rolling in off the North Sea from the east as soon as the Sun’s rays became weakened by its falling altitude in the northwestern sky. I did however manage to get some quick peeks at the lunar surface at powers of 250x (6mm Baader ortho) and at 375x (4mm Revelation Plossl). I can report that both ‘high power’ oculars delivered very sharp and detailed images of the lunar regolith in twilight, demonstrating that these powers can be productively used on extended objects like the Moon and the planets in the foot ‘scope. That said, I’ve used nearly double these powers on sub–arc second double stars in work conducted during the summer and autumn of last year.

Alas, the courier never showed up today with the eyepiece……ho hum.

Maybe tomorrow lol!

Date: May 23 2018.

Time: 12:20 UT

The Explore Scientific 34mm 68 degree Maxvision eyepiece.

















Well, the new 34mm eyepiece has finally arrived.


It’s a scaled down version of the venerable 40mm.

The 34mm Maxvision ocular(left) in comparison to its 40mm counterpart(right).

















What I especially like about this series of wide angle eyepiece is that they provide excellent performance in a no–frills package. It came in a plain box with no colourful logos and no advertising brochures. Compare them to the now discontunued Meade SWA incarnations;

The now discontinued Meade Series 5000 Superwide Angle eyepiece family.









I seem to recall that the Meade 34mm SWA retailed for £249, but were reduced in price for clearance after they were discontinued. Many retailers do not offer the Maxvision series but appear to be selling a hermetically sealed (argon purged) product with a re–designed body for £219.

So, I was able to purchase essentially the same eyepiece for a little over half the price of the latter. That’s what I call a bargain!

You might need to shop around to get your hands on these eyepieces, but I was able to secure this one from Rother Valley Optics.

Of course, I could have gone for some 82 degree wide angle eyepieces which would provide a slightly larger true field (approximately 1.6/7 degrees), but my eyes seem to prefer 68 to 70 degree fields.I appreciate that this is a highly personal choice though.

The Maxvisions seem to be enjoyed by many amateurs. See this thread, for example. Some amateurs prefer to de–cloak them for some reason, perhaps to pare down their weight or to make them look more appealing, but I have never seen the need to do so.

The stubborn haar is still with us and though my skies are currently blue, it will likely roll in off the North Sea later this evening.

No matter, I’ve done good!

Time: 14:05UT

Gaius, the author’s beloved 80mm f/5 ShortTube refractor fitted with the 34mm eyepiece.

















I couldn’t wait to see how it performed, so I mustered my 80mm f/5 achromatic telescope and inserted my Televue 2 inch Everbrite diagonal and in went the 34mm Maxvision.


The eyepiece delivers a wonderful, wide field at 12x giving a 5.75 degree true field. The field stop is hard and well defined and contrast appears to be excellent. With these eyepieces one can readily adjust the distance of the large eye lens by rotating the upper section to provide the optimal level of viewing comfort.

I’m currently writing a book that is wholly dedicated to the ShortTube 80 achromat and one of those chapters will de devoted to choosing eyepieces for use with it. I hope to perform more critical tests on the night sky in due course.

The 34mm will also serve Octavius, my 8 inch f/6 Newtonian, by delivering a power of 35x in a field just under 2 degrees in extent.

Carrying on the work with the foot ‘scope.

















Time: 21:45 UT

Contrary to what I expected, the haar did not roll in in the late evening, and it is still clear just now. I set the foot ‘scope out again at 19:00UT and was able to continue my high magnification testing of the early gibbous Moon. I began observing at about 20:40 UT when the Moon had past the meridian and was located at an estimated altitude of about 37 degrees. This was a good altitude to test the defining power of the 12 inch. On fine days like this, the air can be very tranquil in the minutes immediately after sunset and so I began with 200x (Parks Gold 7.5mm). Eventhough the sky was far from dark at this time, the lunar regolith presented with razor sharpness and very good steadiness. Ditto at 250x. Then I attached my Baader 2.25x Barlow to the 7.5mm Paks ocular which delivered a power of 450x. Carefully focusing, I was delighted to obtain a wonderfully sharp and (still) fairly stable image. Having the facility to use the microfocuser proved very useful.  Looking at the ragged crater walls, I could see details which I do not recall observing in my 8 inch at high powers.

This was a most satisfying result! This instrument is indeed capable of very high powers on extended objects like the Moon and a solid indicator that the optics are of high quality, but I am also fortunate enough to live in a place where the seeing will allow a 12 inch to work beyond the remit of my 8 inch telescope.

I’m away out again to conduct some further observatons and to test the 34mm Maxvision ocular. Shall report back later.

Time: 22:45 UT

Well, the haar has come back lol. It was rolling in as I was writing the last section of the blog. But there was a few suckerholes in the sky and I naturally took advantage of them. My first target was Capella now located quite low down in the north northwest. Charging the foot ‘scope with the 34mm Maxvision I can report excellent results. The bright first magnitude star remained pinpoint sharp across the vast majority of the field while wearing my eyeglasses (which correct for the astigmatism in my eyes). Only at the extreme edge of the relatively massive field did the star show signs of field curvature, coma and astigmatism. The same was true of Polaris located at an altitude of 56 degrees above my northern horizon.

Intriguigingly, I also tested the same eyepiece on my 80mm f/5 achromat. The results were broadly the same but I would say that there was slightly less aberration at the extreme edge of the field of view! It had field curvature and astigmatism but not much in the way of coma. Thinking about this for a few moments, I figured that this slightly better result is due to the fact that even at f/5 an achromatic doublet has very little coma inherent in the design. This is a relatively unsung virtue of modern refractor optics.

So a very good result, which left me very satisfied indeed. The eyepiece does exactly what it says on the tin. No hyperbole; just great performance at an excellent price!

Happy camper.

Need to pack up all the toys now and return to barracks.

Date: May 25 2018

Time: 00:05 UT

Just a quick report from tonight. I only fielded Octavius, my 8 inch f/6 Newtonian this evening to test out the 34mm Maxvision ocular. True to form, it delivered fantastic views and just that little bit better correction right at the edge of the field. I’m going to have an absolute ball with this when dark skies return later in the summer!

My main high resolution target was 78 UMa, conveniently located very near Alioth (Epsilon UMa), one of the stars that form the handle of the Ploughshare. My notes inform me that I’ve not revisited this system for close on three years. And it’s got tougher! The separation was about 0.84″ in 2015 but judging by observations conducted tonight using a power of 500x in good seeing conditions (II) at its currently high altitude above the horizon, I would say that the companion is nearer 0.7″. It was spotted roughly east of the primary and pretty much kissing it but I need to make more observations, especially with the foot ‘scope. The primary is magnitude +5.02 and the secondary +7.88.

More on this later.

Time: 10:25 UT

Setting up the 8 inch is easier on the back than doing the same with the 12 inch. There is quite a step up in mass and bulk volume as the image below suggests;

A 12 inch Dob(right) is considerably bigger than the 8 inch(left).

















Still, I am more confident than ever that this will also be matched in terms of performance.

I found out that the companion to 78 UMa orbits the primary in just over a century and it’s currently rapidly closing, reaching its minimum separation in 2026 with a separation of 0.48.” Dynamically, this will be an excellent subarcsecond system to study over the next few years and both the 8 inch and 12 inch Newtonians will be pressed into service monitoring its movements. More details here.

This is just one of many fascinating high resolution targets that you can study using telescopes of this size.

Right folks, that’s your lot for this blog. I hope you have enjoyed its content and that it gives you some encouragement to get out there and enjoy the glories of the night sky.

Update: June 4 2018

Since I intend to get a lot of use out of the foot ‘scope, I invested in a small trolley that can help lighten the load of carrying the large optical tube from idoors to the outdoors and back. All I have to do is place the optical tube on the platform and secure it in place using two ropes (supplied with the trolley). It is thereby easily moved from place to place using a couple of small ramps.

I attach a couple of pictures of the ‘scope on the trolley, for interest;

The foot ‘scope on its trolley.
















The tube is kept in place by two flexi ropes.

















The trolley can also be folded down to a neat size for easy storage.

The trolley collapses for easy storage.

















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



De Fideli.

Further Adventures with a 3″ Achromatic..

An amazing performer; the Orion SpaceProbe 3 reflector.
















Dedicated to John Wall (1932–2018).

a chromatic: literally, without colour.

There has never been a better time to begin the hobby of telescopic stargazing. In past generations, owning a good telescope often proved to be an expensive venture, typically involving many months or even years of saving up. Thankfully, such days are well and truly behind us. Today, you can purchase a decent quality telescope for a very light financial outlay. Indeed, I always advise novices not to spend a great deal on their first telescopes, especially if they are unsure whether or not they intend to pursue the hobby in the longterm. In addition, many people will end up being ‘casual’ or ‘occasional’ observers and so splashing out lavish sums of money on an instrument that sees little net use doesn’t make a whole lot of sense.

In this capacity, one of the best novice ‘scopes I have personally come across is the Orion SpaceProbe 3 reflecting telescope (pictured above, fully assembled), which set me back about £70. That money bought me a very good 3 inch (76mm) telescope, together with a decent mount and two good quality eyepieces delivering magnifications of 28x (using the 25mm ocular) and 70x (when the 10mm eyepiece is employed) and an excellent instruction manual written by an experienced astronomer to show you how to set up the telescope properly, as well as guidance on how to keep the optics in tiptop condition.

All good starter ‘scopes need a good instruction manual.

















The Orion SpaceProbe 3 is the latest incarnation in a long line of Newtonian reflecting telescopes, so called because its ingeniously simple design was invented by Sir Isaac Newton around 1668. Over the years, the Newtonian telescope has been steadily improved and refined so much so that today it is arguably one of the most popular kinds of astronomical telescope on the market. Generations of skygazers have enjoyed the crisp, bright images served up by these telescopes, allowing them to conduct detailed observations of a wide range of celestial real estate, from the Moon and the the bright planets, to pretty star clusters, nebulae and distant galaxies in the depths of space.

The optical tube displays the basic optical information of the telescope, including its aperture (76mm) and focal length (700mm).

















The Space Probe 3 telescope has a focal length of 700mm and we need to know this number in order to calculate the magnification being used with any given eyepiece. Fortunately, it’s a simple calculation; just divide the focal length of the telescope by the focal length of the eyepiece. So the 25mm ocular produces an enlargement of 700/ 25 = 28x and the 10mm eyepiece provides a power of 700/10 = 70x. Although these will give very pleasing views at ‘low’ and ‘medium’ power, one will eventually need to stretch the magnification some more to get the best views of high resolution targets like the Moon and bright planets. Furthermore, by dividing the focal length by the aperture, i.e. 700/76, we obtain a quantity called the focal ratio of  9.2 or f/9.2. The significance of this number will become important as I elaborate on the optical quality of the telescope in due course.

My field testing over the last two months has clearly shown the potential of this little telescope. A good instrument ought to garner sharp images at powers of 50x per inch of aperture. So according to this reasoning, a 3 inch reflector ought to handle 150x. But I can assure the reader that this telescope can handle considerably higher powers and these high powers can prove very useful for certain kinds of astronomical observations. I have used the instrument profitably at powers of 210x or more but one must also bear in mind that as one pushes the magnification to these high values, the images become rather dim owing to the small 3 inch mirror gathering the light.

By far the most economical way to achieve a greater range of magnifications is to invest in one or two Barlow lenses. Typically they will boost the power of any eyepiece by a factor of anywhere from 1.5 to 3 times. You can get a decent Barlow for just a few tens of pounds (it’s always worth watching out for one on the secondhand market too) and when skillfully chosen, can turn two eyepieces into four or even six. For example, a 2x Barlow will enable the two eyepieces supplied to give additional powers of 56x and 140x. For this particular study, I employed 2.25x and 3x Barlows, providing high powers of 158x and 210x, respectively, when coupled to the 10mm eyepiece supplied with the telescope.

The eyepieces and Barlows used with the telescope. From left to right: the 25mm ocular, the 10mm ocular, the 2.25x and 3x Barlow lenses.

















One of the most attractive features of the telescope and its mount is its overall weight; just 8.4 pounds (3.8 kilos)! That means that most anyone can move the fully assembled instrument about. The lightweight, but strong aluminium tripod can be collapsed or extended for seated for viewing or by standing. I decided to use the instrument without its accessory tray so as to maximise the stablity of the tripod. In addition, I elected not to attach the slow motion control bar. This is a strategy I have adopted for many years now, as I like to keep the up−down (altitude) and sideways (azimuth) motions to be as free as possible whilst in ue. With many hours of practice, I have learned to nudge the telescope along smoothly and with minimal vibrations, even at high power. I accept that this is essentially a learned skill and that others may not be happy with it. Only time spent at the telescope can ultimately sway you in one direction or another, and I would encourage as much experimentation as possible in this regard.

To get the very best images out of this telescope, the user must ensure that the optics are accurately aligned. The user manual with the supplied collimation cap and Philips screwdriver will enable you to accurately execute such a task. Experience shows that once this is done, the telescope retains very accurate optical alignment, even after being moved from indoors to the outside many dozens of times. This fine tuning of the optical train will make a noticeable difference to the high power views especially.

By and large, telescopes are not status symbols. How they look counts for practically nothing in the scheme of things. That said, this telescope is well made and is handsomely finished. It ‘looks’ like a ‘proper’ telescope and performs like a ‘proper’ telescope. The rolled aluminium tube is finished in an attractive British ‘racing green’. Some readers concerned more with appearances than anything else (an ugly reality for some, unfortunately) will no doubt fuss over whether or not it ‘looks the part’ and may falsely ascribe importance to what ‘others’ might think. This rather sad state of mind can be entirely dispensed with however, when one realises that amateur astronomy is very much a small ‘goldfish bowl’. The vast majority of folk I have shared my telescopic experiences with know next to nothing about telescopes and can’t discern anything from its appearance. Indeed, you’re as likely to find a telescope like this in a New York penthouse balcony than in a tenement of a working class community. Telescopes are just not like cars! So, if you’re concerned about something as trivial as ‘looks,’ you’re probably in the wrong hobby!

To get an idea of how good the optics are in these telescopes, it pays to take the instrument out during daylight hours. I like to observe nature with as many of my telescopes as possible and usually select a good spot in my garden, out of direct sunlight, and give the instrument a few minutes to settle down in its new environment. To work at its best, any telescope must be allowed to equilibrate with its ambient environment. Failure to do so will provide less than optimal (read disappointing) results, especially when the telescope is ‘pushed’ to high magnifications. I recommend starting with the lowest power eyepiece; this will be the 25mm Explorer II ocular supplied with the telescope delivering 28x. I usually select a distant tree top a few hundred yards distant or some such which I can zoom in on. Care must be taken to avoid observing targets over possible heat sources, such as rooftops and the like.

Once a suitable target is chosen, crank up the magnification gradually, carefully touching up the position of best focus by moving the drawtube housing the eyepiece slowly back and forth until the sharpest possible images are produced.

Good focusing is an essentail skill, especially when attempting to ‘push’ the magnification of the telescope.

















By engaging in such an activity, I have discovered that the telesope can take high powers in its stride. The images remain crisp and sharp right up to 210x and beyond, especially on bright sunny days. This comes at the expense of image dimming though; higher powers yield progressively dimmer images. This image quality is no doubt facilitated by the high focal ratio of the telescope (f/9.2 in this case). When the focal length is long in comparison with the aperture of the ‘scope, geometrical aberrations are minimised; less field curvature, coma, distortion, spherical aberration, astigmatism etc. This alows for the use of simpler and less expensive eyepieces so that using the telescope will not create a ‘black hole’ with your resources.

Oh deary me!












In this way, you will discover that this telescope is a very sharp shooter that will embarrass owners of much more expensive telescopes of comparable aperture. The images you will enjoy are true and honest; a simple consequence of the laws of optics and good execution. Here’s an image taken my the US−based amateur, Joe Roberts, who took the time to image the first quarter Moon at prime focus (be sure to click on the image for a good close up) with the same telescope albeit on a sturdy motorised equatorial mount. I hope you will agree that this little telescope is no toy!

More a hindrance than a help: the EZ finder that comes with the telescope.


















One of the Achilles’ heels of this telescope package might not be uncovered until one spends a good few hours in the field. Specifically, many decent−sized telescopes come with the equivalent of a ‘rifle sight’ or ‘finder’ telescope, which usually attaches to a bracket found on the top of the main telescope, adjacent to the focuser draw tube. Once aligned with the main telescope, it serves as a very useful tool to find and centre objects quickly. But the ‘finder’ supplied with the Orion SpaceProbe 3 is not a  telescopic ‘finder’ as such, but a non−magnifying device (the EZ finder) that projects a small red dot onto a plastic screen which the user is required to co−align with whatever object is to be observed in the telescope. However, a few sessions of active use with the EZ finder will convince most of its inadequacy. For one thing, the EZ finder can only be used with the brightest stars and for those who live in towns and cities, where light pollution may be a concern, using it will prove more an exercise in frustration than anything else.

For this reason, I would strongly recommend the user swap this device out for a regular finder telescope; a small traditional finder ‘scope magnifying perhaps five or six times and having an objective (front lens) of about 30mm. These can be purchased on the used market for very little money. Indeed, if you play your cards right, you may find a sympathetic amateur who will provide you with one for free! Mounting such a finder ‘scope will greatly enhance the enjoyment one can have with the telescope. You’ll be able to focus in on much fainter targets, and learn how to ‘star hop’ from one object to another.

Close up of the finder I mated to the scope; note the matching colour and texture of the finder bracket with the focuser and rim of the optical tube assembly. Schmokin’

















Before you can use the finder, it must be aligned with the main telescope. This is easy to do in daylight. Just select a distant target (as far away as posible and at least a few hundred yards in the distance) and centre it the main telescope. Now look through the finder ‘scope and  move the cross hairs of the finder so as  they coincide as precisely as possible with the image in the main telescope. This is usually done by tigtening or loosening a set of screws in the bracket mounting the finder. Once that’s done, move the telescope to a different target and check to see that the subject you have centred in the main instrument is also centred in the cross hairs of the finder ‘scope. If so, you’re ready to rock ‘n’ roll!

The position in which the observer looks into the telescope has a direct bearing on viewing comfort. And the more comfortable the telescope is to use, the more you will use it. In this capacity, the convenient location of the focuser drawtube makes it easy to observe objects situated at low altitudes but it is while viewing targets high in the sky that the great utility of the Newtonian design shines through. As a former refractor enthusiast, I certainly do not miss the extraordinary degree to which one has to crouch down into very uncomfortable positions near the ground in order to view a high altitude target for any length of time. The simple truth is that Newtonians dispense of much of this hardship. Because I value my back and my posture, observing with the Orion Spaceprobe 3 provides a good way forward.

Every budding telescopist needs a guide book of sorts. It can be hard to know what’s what, observing from a bright, suburban sky, and from a dark site, where the full glory of the heavens is manifested, it’s very easy to get confused. That’s where a simple guide to the night sky is so useful. It will be prove indispensable as your knowledge and observing skills develop. There are many good literary guides available to the modern amateur. I especially like Ian Ridpath and Wil Tirion’s Stars & Planets (Collins 2017). It’s strength lies with its simplicity. You can use the seasonal and monthly maps to find the outline of a constellation you wish to explore and then home in on your selected target(s) for the evening. The lunar maps are very good too. Overall, I have found it an invaluable aid to small telescope forays in the northern hemisphere, but is equally at home under an antipodean sky.

The new edition ( October 2017) of a favourite observing guide.

















Finally, though it may seem a bit old fashioned nowadays, I recommend that all observers adopt a culture of regularly recording the sights and sensations one experiences while at the telescope. Notes are an important thread to the past.  It’s amazing how much one forgets as the years go by, and it is so reassuring to have the means of consulting earlier work in matters that may prove important at some later time.







OK. With all that said, we’re now ready to begin an adventure together under the stars, exploring something of the extraordinary riches of the heavenly creation. It is fitting to begin this journey with the brightest and most accessible object in the night sky; our glorious Moon.

Oona: a perfect ‘scope for moongazing.


















Date: January 31 2018

Time: 22:00 UT

Conditions: Clear, bright sky, very little cloud, bright full Moon.

Temperature: 0C

Tonight is a Super Blue Moon. This means that the Moon is bigger and brighter than average (that’s the ‘super’ bit). It is also the second full Moon in the month (making it’ blue’), the last one occurring on January 2nd last. Inserting the 25mm Explorer II eyepiece and focusing the telescope shows a big bright orb. Indeed it’s almost dazzlingly bright, prompting some observers to reach for a neutral density filter to cut away some of the glare and reduce eye strain. Notice also that the reflected light from the full Moon makes the background sky very bright, drowning out the light of many of its fainter stars.

Did you notice that the image of Moon is both upside down (meaning north is at the bottom and south is at the top) and back to front (meaning east and west are the wrong way round)?

All of this is completely normal with a Newtonian telescope. Indeed, spatial orientation is of little importance in the pursuit of astronomical bodies. You’ll soon get used to it!

Now, looking at the Moon itself with the 25mm eyepiece delivering 28x. Notice how big the entire field is. Indeed, you can easily see that it will fit about three full Moons from one side to the other. Since the full Moon subtends an angular size of about half a degree on the sky, this gives you an idea of how large the field is in the 25mm Explorer eyepiece; about 1.75 degrees. That’s plenty big enough to see the vast majority of deep sky objects, as we shall see on other evenings.

Chances are you’ll have also witnessed two ray craters on the lunar surface. Down near the bottom of the Moon (as you observe it in the northern hemisphere) is Copernicus and the one near the top is called Tycho. Can you see how rays of bright matter seem to stream from these craters? The rays are caused by ejected material gouged out when a large, rocky body collided with the lunar surface in the distant past, ejecting huge quantities of material away from the crater and in all directions (that is, radially). Such ray craters are very old: Tycho is believed to have formed some 100 million years ago, while Copernicus is thought to be 10 times older still (so a billion years or so).

The two prominent ray craters visible in the telescope; seen here in the correctly orientated view.












Because your telescope is a reflector, it shows the true colour of the lunar regolith. Looking closely at its surface will convince you that it has many shades of white and grey, revealing something of its mineral content and age.

Next, remove the 25mm eyepiece and replace it with the 10mm. After centering the Moon and refocusing; you will note that the field of view is considerably smaller and yet it’s still larger than the size of the full Moon. Indeed, this 70x eyepiece serves up a fairly generous field of view of about 0.7 degrees.

It follows that as the magnification increases for a given eyepiece design, the field of view shrinks.

This observing session will have familiarised you with the magnifications and field sizes for your two eyepieces. These will be useful data as we plan our observations of other celestial bodies.

Alas, observing the Moon while it is full is the absolute worst time to see many of its most inspiring features. To see the great mountains, valleys, craters and rilles; we’ll have to wait until the Moon proceeds through its last quarter and crescent phases. We shall return in a few days when it begins to wane.

Be sure to tune in again soon; you won’t be disappointed!

Date: February 5 2018

Time: 00:35UT

Conditions: good, steady conditions, almost totally clear, cold.

Temperature: −1C

I’ve been watching the Super Ball!

No, that’s not a typo!

It’s a lovely winter night here in the glen. The Moon began to rise about 10:30pm local time, but I waited a couple of hours before beginning observations of the waning gibbous Moon. Charging the telescope with the 25mm Explorer eyepiece, I watched in sheer amazement as our wonderful natural satellite rose above the tree line in the east. Even with the 28x eyepiece, there was a wealth of fine detail to be seen. At low altitudes the air roils quite a bit. That’s totally normal. At low altitudes, you are looking through a dense swathe of air, which generates a bit of turbulence. At these low altitudes, you can even make out subtle colour differences in the lunar regolith. Specifically, the Moon takes on a very light, rose tint. This is also to be expected, as at lower altitudes there is more dust which scatters blue light more than red (a phenomenon called Rayleigh scattering). I find it very beautiful! Compare its colour again when it rises a lot higher in the sky. That comely rose tint all but disappears. Only its silvery face presents itself when it rises above the dust line.

Below is an image of how you should see this waning gibbous in the low power field of your 3″ reflector. I simply rotated and inverted a Wiki Commons image of the Moon at this stage in its phase. That said, I perceive the contrast in the telescopic image to be noticeably better than this image.

The waning Gibbous Moon as seen in the low power eyepiece of the telescope.















As the minutes pass, the Moon rises higher and the image becomes steadier. When it reaches a decent height, say 15 degrees or so, remove the low power eyepiece and insert the 10mm ocular, delivering 70x. The image should remain nice and crisp and even more detail should be discernible. Use a Moon map to try to identify some of the sights your eye meets with. As the Moon rises above 30 degrees altitude (so about one third of the way from the horizon to the zenith), use a Barlow lens to boost the power still more. If the optics are working half decently and are properly aligned, you ought to get good sharp images at 150x or higher, if the air remains steady. That the images are crisp and clean even at these high powers testifies to the extraordinary value of this economical little telescope.

Intriguingly, February 2018 will not have a full Moon (it will be almost full though lol); something that hasn’t happened since 1999. And, as if in recompense, March 2018 will have two full Moons; one on the 1st and the other on the 31st. So March 2018 will present another Blue Moon if you’ve missed the apparition in January.

I like to name all my telescopes. This little one is called Oona.

Wee Oona; ready for action.

















Date: February 6 2018

If you follow the phases of the Moon faithfully with the little Space Probe 3 telescope, you’re sure to have an absolute ball. It will serve up beautiful images time and time again. Arguably the best times to observe our natural satellite is between the half−illuminated and crescent phases. You will be astonished at just how much this instrument can reveal!

When taking the telescope and your eyepieces from the cold night air back inside to a warm indoor space, chances are you’ll notice that some condensation may form on the optical surfaces, in much the same way as steam from a kettle fogs up a cold window. This effect of fogging up is more inconvenient than anything else, but you can largely avoid it by capping your eyepieces and the telescope before you bring them back indoors. Under no circumstances are you to rub the lenses or the mirrors while they have dew on them. If you see signs of condensation, just let it evaporate away before capping up the optics. These simple measures will ensure that your equipment will remain in top condition for many years to come.

Observing the Moon is only the first step in enjoying the Orion SpaceProbe 3. As we shall discover, a rich variety of celestial objects are within easy reach of this little telescope. All we need is another clear sky to explore them.

The Ever Changing Sky

The Northern sky on February evenings.

















The night sky is constantly changing; minute by minute and hour by hour, as the world turns on its axis and races around the Sun. Consulting the all−sky maps presented on pages 30 and 31 of Ridpath and Tirion’s book, you can see how the February sky appears in the northern hemisphere. Looking south, we see Virgo, Leo, Cancer, Gemini and Taurus, as if in some grand procession, moving from east to west. Concentrating on the constellation of Cancer, the celestial Crab, featured on page 97, I have selected a single object worth investigating with the telescope; The Beehive Cluster (M 44).

The constellation of Gemini in our guide book. M 44 is seen circled near the centre of the consellation.

















The accompanying notes featured on page 96 give us enough background information in order to make sense of what the telescope will reveal. M 44 is an open cluster, also known as Praesepe (the Manger), the authors inform us. It is large, covering about 1.5 degrees, and consists of some 50 stars ranging in glory from magnitude 6  and fainter. It even tells us how far away the cluster is; a mind−boggling 592 light years according to measurements made by the Hipparcos satellite. It ought to be visible to the naked eye as “misty patch” from a dark country sky, making it easy to track down.

Time: 23:00−23:30 UT

Seeing: Good, clear, cold.

Temperature: −3C

I took the telescope out for a short spell tonight after work. It remained very clear all day, and on into the evening. It was another lovely vigil with a light dusting of fresh snow to brighten up the landscape. So, before the Moon came up, I ventured out when I knew the cluster would be highest in the sky, that is, when it’s due south. Where I live, M44 is a very easy naked eye object. Just like the authors described, it’s a fairly conspicuous “misty patch” that is easily framed in the finder ‘scope and the main telescope proper. Only one eyepiece was used tonight; the 25mm Explorer II, delivering 28x. It framed the cluster perfectly, where dozens of stars of various degrees of glory pepper the field of view. And it’s not at all hard to see why its more popular name, the Beehive Cluster, is alive and well.  With a little concentration, you can make out a soft, yellow colour in the brighter members; a good sign that this cluster is fairly mature in the scheme of things. I made a simple sketch of what it looked like (see below). If you are warm and comfortable, sketching can be a whole lot of fun, even in the cold of winter. I simply try to memorise what the field is like for 10 or 15 minutes, nudging the telescope along with one finger as the Earth rotates beneath my feet. Once I’m indoors I make the sketch. Little Oona frames lots of things in the sky very well.
















There are, of course, other ways to make a sketch. Many do so while at the telescope. In order to do that, it’s advisable to protect your night vision as much as possible. You see, in the dark, your pupils dilate to take in as much light as possible. This is a natural biological response to low light conditions. Fortunately, red light does not appreciably interfere with this dark adaptation, and so many amateurs choose to make their telescopic sketches of deep sky objects under the illumination of a low intensity red light source. Whatever way you choose to carry out your sketches, I hope you will find the activity both relaxing and rewarding.

Date: February 8 2018

Some Musings on Optics

Anyone who has spent a decent amount of time with this telescope and knows how to keep the optics well aligned will surely tell you that the images are exceptional for its meagre monetary value. The reason for the low cost is the simplicity of the optics. The prmary mirror is spherical rather than a true parabola. Spherical surfaces are much easier to execute well in comparison to their parabolic counterparts, which need further figuring to ‘deepen’ the centre of the mirror. But if its aperture is kept small and the focal length is large in comparison, there is absolutely no need to modify the sphere into a parabolic shape. To get an idea of just how good a 76mm (3″) mirror with a focal length of 700mm can be, take a look at a computation made by OSLO (an optics package);

An OSLO analysis of a perfect 76mm f/9.2 spherical mirror. The reader should concentrate on the red underlined data in the lower box.













If your mirror is a perfect sphere then you have a wavefront rating of 1/12.5 PV. Put another way, a completely error free mirror with these specifications would have a Strehl ratio (seen on the right above) of 1.0. The analysis shows that the actual value is shockingly close to absolute perfection: 0.97!

The conclusion is very simple to interpret: small aperture and long focal length spheres are so close to a parabola it makes little difference.

Of course, we also need to consider the aberrations introduced by the secondary mirror, but suffice it to say that unless the secondary is a complete lemon, it’s very likely that the overall quality of the optics will be very high indeed, good enough to impress anyone who takes the time to spend a few hours with it.

Star testing provides a good way to test how well the optics behave in the field. To do this, make sure the telescope has accurately aligned optics and has had time to cool down outside. Next, select a bright, first magnitude star, situated high up in the sky. For example, Capella is just perfect from my far northerly location. Select a high power; anything between 100x and 150x and carefully focus it. You ought to see a tiny sphere (the so called Airy disk).

The Orion Spaceprobe telescope supports the secondary mirror using a 3 vane spider (b above) and yields six diffraction spikes that are very hard to see except round the brightest stars.


Now, if you slowly rack the focuser inward, you will begin to see a set of concentric, Fraunhofer diffraction rings around a dark central spot.The shadow of the three spider vanes will also be seen.

And when you then rack the focuser outward, past the position of precise focus, the diffraction pattern should look identical (or almost so). This is what you want to see in a telescope offering very good to excellent optics. Star testing can provide much information about your telescope, but it’s always best to conduct such tests under the best conditions your local environment will provide, and (preferably) over a few nights. If you don’t get such textbook perfect results, don’t fret. I mean, if you’re already happy with the high power images your telescope is serving up during the day, and again by night, you have a winner and you needn’t worry any more.

Oona star tests very well, showing that her optics are of very high quality. Mass production has clearly come a long way with these little telescopes!

Date: February 9 2018

Time: 19:15 UT

Temperature: 0C

Conditions: good transparency, mostly clear, breezy

Orion is a majestic constellation to explore with a small telescope.

















It was a bright and clear day today and the the sky has remained largely cloudless after dark. The mighty constellation of Orion the Hunter is now approaching its highest point in the sky so is nearly due south. It will present a good opportunity to examine an entirely different kind of deep sky object. Tonight, we will pay a visit to the Great Nebula in Orion. Our guide book on page 197 shows me exactly where to look: immediately beneath the middle star in the Hunter’s belt. The notes of page 198 inform me of some sensational facts about this target; the object, known also as M 42, is a gigantic ball of gas lit up by young stars that are forming inside it. The authors say M 42 lies about 1500 light years away and that it is almost 20 light years across, and much more. Time to set up the telescope once again for another adventure under the stars.

Time: 20:30UT

The Great Nebula in Orion is also easy to spot with the naked eye. A couple of seconds of scrutiny will convince you that it is quite unstarlike; more like another ‘misty patch’ than anything else. Starting with the 25mm Explorer II eyepiece, the telescope clearly reveals its nebular nature in a pretty hinterland of bright stars. If you carefully focus on the nebula, the same eyepiece should allow you to just make out four distinct stars at the centre; this is the famous Trapezium; very young and hots stars that are estimated to be only a few million years old. They formed out of the cool gas that surrounds them. Ordinarily, a gas cloud is not luminous in and of itself. It is only by virtue of the radiation from the stars that form inside it that renders it visible, just like a neon light bulb.

Now switch to the 10mm Explorer II ocular for a better view of this magnificent structure. At 70x, it is much easier to see the four stars making up the Trapezium, as well as much greater detail in the nebula itself. My eyes can clearly discern colour within the nebula; a very pale green. The colour becomes easier to discern as one’s eyes adapt to the darkness. The visual colour of M 42 is quite unlike that produced by a CCD camera however, which picks up vivid blues, pink and red, owing to its greater sensitivity to light. Still, just detecting some colour provides a real visual thrill.

Just to the north of M42, my eye meets with a ‘fuzzy’ star. This is in fact another nebula; M 43.  After several minutes of study, slowly nudging the telescope along as the object moves westwards through the field, I made a quick sketch of my impression of the view as seen through the little 3″ reflector.

M 42 as observed on the evening of February 9 2018 using the 76mm f/9.2 reflector. South is at the top and west is to the left.
















Larger telescopes will give even more compelling views. That’s because larger telescopes collect more light and deliver that light to your eyes. A fully dark adapted human eye allows your pupil to dilate to about six or seven millimetres. That is the maximum ‘aperture’ of the human eye. But when you look through the telescope, that 7mm is replaced by a mirror fully 76 mm in diameter! As you can imagine, it collects many times more light than you can with your naked eye because its light collecting area is so much greater; and that allows you to see much fainter objects.

The orion SpaceProbe 3; a wonderful little light cup.

















Date: February 11 2018

Time: 21:10−21:20 UT

Conditions: turbulent, frequent sleet & snow showers, very cold in the wind.

Temperature: −1C

Oona(right, background), accompanied by Octavius, my newly flocked and insulated 8−inch f/6 Newtonian reflector.

















I spent Saturday afternoon lining the inside of my 8 inch f/6 Newtonian reflector with cork and then covered it over with flocking paper. This evening, I decided to test drive the 8 inch, which I had planned to use along side the 3 inch reflector, but the frequent interruptions from snow showers forced me to retire the larger instrument after about 15 minutes; I did however gather some useful data on a few tricky double stars.

Because the 3 inch telescope is so lightweight and ultraportable, it was the ideal instrument to use in these very mercurial conditions. And it allowed me to greatly extend my gaze. Everything we have visited thus far with the 3 inch reflector lies entirely within our own galaxy, the Milky Way. Tonight though, I spied the Plough asterism looming large in the northeastern sky and decided to try my hand at tracking down the famous Messier duo, M 81 & M 82; a wonderful pair of galaxies located at a distance nearly four orders of magnitude further away than even the Great Nebula in Orion!

Charting a course.

















The pair is easy to track down in a dark, moonless sky. Consulting my guide book on page 251, I was able to chart a course for these fairly easily, by drawing an imaginary line from Phecda through Dubhe, and extending that line about twice as far again until I arrived at my destination. Tucked away in an otherwise fairly barren sector of the firmament, my finder could easily make out 7th magnitude M 81, and, with a wee bit more concentration, M 82 also. Once again, only one eyepiece was used this evening; the trusty 25mm Explorer II eyepiece, which easily framed the duo, separated as they are by about 0.6 angular degrees of sky. M 81 looks fuzzy and elliptical in shape, brightest near its centre and gradually fading towards its edges. M 82 to its north presents as completely different however; more cigar shaped than elliptical. After a while studying the pair, you may come away thinking that M 82 is easier to study, even though it is about four times fainter than M 81. Both galaxies lie at a distance of 12 million light years; an utterly unfathomable scale.

I made a quick sketch, shown below, of M81 and M 82, and its hinterland through the SpaceProbe.

Messier 81 & 82, as seen through the 3″ f/9.2 reflector on the evening of February 11 2018.

















There are many more galaxes within reach of the little achromatic, and which will take us even further afield. Best to wait ’til better weather sets in though.

Date: February 14 2018

Time: 20:40UT

Temperature: 4C

Conditions: Mostly clear, some cloud interfering with observations, milder than of late, windy.

After enjoying a romantic Valentine’s supper together with my wife, I ventured outside to see how the sky was shaping up, and as luck would have it, it seemed very inviting to continue our adventures under the stars with the Orion SpaceProbe. As promised, we’re going to try our hand at objects significantly farther away than our former targets; specifically,  a trio of galaxies in the constellation of Leo the Celestial Lion, which will be very well placed later this evening. These galaxies are located about three times farther away than either M 81or M 82, so about 35 million light years distant from our galaxy, the Milky Way.

Our targets tonight are located in southern Leo, shown just above the tip of the pencil in this photo.

Consulting my guide book on page 169, I can clearly see the location of these galaxies; M 95, M 96 and M 105; which should be captured in the low power (28x) field of the 3 inch telescope. That said, these ‘island universes’ are considerably fainter than M 81 & M 82 and so will be a bit more challenging to see (my guide book quotes both M 96 and M 105 as having a magnitude +9, whereas M 95 is fainter still at + 10).

I shall report back later to tell you how I got on. Fingers crossed!

Time: 23:45UT

Alas, it has totally clouded over, so I will need to abort this activity tonight and try again another night.

Date: February 15 2018

Time: 14:00 UT

The weather is not always in harmony with human ambition. Meteorology may be a mature science, but it can’t yet be relied on with 100 per cent accuracy. There will always be discrepancies between what the forecast predicts and what you actually experience. It just comes with the territory of any amateur astronomer. That said, such episodes cultivate patience and preparedness; virtues in their own right.

It is a New Moon today, so a thin crescent should appear in the sky over the coming evenings. But once that Moon sets, it will be good and dark enough to ferret out those galaxies in Leo. I will report back again as soon as an opportunity presents itself.

Date: February 16 2018

Time: 00:30UT

Conditions: quite windy, some clear spells, remaining more mild than of late.

Temperature: +4C

I managed a short spell with the SpaceProbe just after midnight. By then, Leo had moved into a favourable position in the south southeast. I centered the finder ‘scope on the star 53 Leonis, which lies just south of the targets in an otherwise rather empty region of sky. Then, charging the 3 inch with the 25mm Explorer II eyepiece, I nudged the telescope about one angular degree to the north norhwest and scrutinised the field for signs of faint fuzzies. Sure enough, both M 95 and M 96 show up well in the little SpaceProbe at 28x. The more easterly M 96 is slightly brighter than M 95. The latter appears rather circular with a noticeable central condensation. To my eye, the fainter M 96 looks a wee bit more elongated along its north−south axis. Both of these objects are classed as barred spiral galaxies. Moving this pair to the southern edge of the field, your eye will pick up the giant elliptical galaxy M 105, appearing as a faint glow.

Although the strong gusts of wind and the constant interruption from clouds prevented me staying out for very long, you can visit another delightful trio of galaxies directly east of these objects; specifically M65, M66 and NGC 3628, also featured on the map above. All shining with magnitudes of about 9, they present as an equally challenging target for the 3 inch reflector. Do give them a visit if your skies permit.

Date: February 20 2018

Time: 14:00 UT

We’ve only just begun to sample the riches of the deep sky with the 3 inch reflector. By studying the maps provided in the guide book, you can explore many more, and all in their due season. The more you use the instrument, the more proficient you will become at finding these objects in the night sky.

I would now like to call your attention to an exceedingly rich cache of double and multiple star systems that can be studied with this little reflector. These objects are a particular favourite of mine, so I hope you will indulge me a little.

The world of double and multiple star systems.

















On page 282 & 283 of our guide book, the authors discuss these fascinating objects. Our star, the Sun, is alone, but many stars in the firmanent, perhaps the majority, occur in so−called binary or multiple star systems, where each component is bound up by the gravitational attraction of its other stellar members. A few, as we shall discover, are not true binaries at all. They just happen to be situated very close to each other from our vantage but are not actually physically connected. Such targets are called optical doubles.

Like the many other classes of deep sky objects, double stars come in a variety of levels of difficulty; from the easy to difficult. Fortunately, the easiest double and multiple stars to see through the Orion SpaceProbe are also amongst the most beautiful. If the weather cooperates this evening, we’ll take our first steps into this fascinating sub−discipline of amateur astronomy.

Diviner of double and multiple stars.

















Time: 22:45−23:15 UT

Conditions; Cold, partially clouded over, decent clear spells.

Temperature: 0C

I managed a few simple drawings of some double and multiple stars near the north ceslestial pole. I had intended to sketch Castor A & B but was clouded out before getting to it. I will discuss these systems later.

Some simple sketches of double stars in and around the pole.

















The above drawings reveal some easy double and multiple star targets near the north celestial pole. Where I live at 56 degrees north latitude, all of these systems are within easy reach, owing to their high altitude. Mizar is the middle star in the Plough handle, now situated high in the eastern sky. Closer naked eye scrutiny reveals that it has a fainter companion, but you’ll get a very pleasant surprise when you examine the system telescopically. For this you will need to use the 10mm eyepiece (70x)  as indicated in the sketch, but you should clearly see that Mizar itself is also double! It is without doubt one of the northern sky’s most celebrated double stars. Curiously, astronomers have discovered that although they appear to be co−located, there is no physical connection between them. Indeed, on page 252 of our guide book, Mizar is found to be 86 light years away and Alcor just 82 light years distant. Thus, we are looking at an optical double here. However, the close−in companion to Mizar is a bona fide companion. This was the first telescopic double ever to be discovered in the history of astronomy, being first sighted by Giovanni Riccioli in 1650.

In my sketch I have also recorded the faint star with a very lofty sounding name, Sidus Ludovicianum, situated between Mizar and Alcor. It is of note only because an intrepid 18th century German stargazer believed it was a new planet and, as was the custom in those days, named it after Ludwig V, his monarch.

Polaris, the pole star, is a completely different animal though. In the low power (25mm) eyepiece, it appears as creamy white star, but if you crank up the power to 70x or higher and closely scrutinise the space in the immediate vicinity of the star you will eventually notice a tiny, faint spark over 250 times fainter than the main star! You might want to increase the power that little bit more with a Barlow lens in order to see it even more distinctly. This is another true member of a gravitationally bound multiple star system, the other constiuents being too difficult to pick up in the little 3 inch reflector. Polaris A and B lie at a distance of 433 light years according to our guide book. Interestingly, Polaris A is a giant pulsating star known to astronomers as a Cepheid Variable. By studying this class of star, astronomers were finally able to elucidate the vast distances to the nearby galaxies beyond the Milky Way in the early decades of the 20th century.

Note: did you notice Polaris moves much more slowly in the telescopic field? Puzzled? Well, that’s because it lies less than one angular degree from the north celestial pole, the rotation axis around which all the stars in the northern hemisphere appear to whirl. This  rather convenient position means it is so much easier to study using the undriven mount of the SpaceProbe 3.

Moving into Canes Venatici (see page 99 of the guide book), yet another showpiece double is ripe for viewing. The brighter member appears white to the eye at 158x and the fainter looks more electric blue to my eye, though reports differ significantly between observers. Indeed, no two observers will report precisely the same colours! This system lies 115 light years away.


Date: February 22 2018

Time: 23:18

Temperature: +1C

Conditions: Cold, hazy skies, good seeing.

I had to tie up some loose ends and couldn’t come back to this as early as I had planned, but I made up for it somewhat this evening. Below are two further sketches I made at the eyepiece of the Orion SpaceProbe 3. The first is Castor A & B in Gemini. Using the map on page 153, I was easily able to pinpoint Castor high in the southern sky at 22:00UT. Centring the star in the 25mm eyepiece, I switched to the 10mm and was delighted to see that even at 70x, the components were well split. But you’ll get a much more majestic view if you crank up the power still more, and, like I said before, this telescope takes high power in its stride because its optics are very good indeed. If your sky is good, test it at 210x and I guarantee you’ll be gobsmacked by what you see!

Both Castor A & B appear pure white as the driven snow, and are quite close together; significantly closer than any system we have thus far visited. More on this tomorrow.

An observation of the close double star system Castor A & B, as seen on the evening of February 22 2018 through the 3 inch Orion reflector.

















As the night marched on, the skies became steadily more hazy and visibility suffered as a result. But I spied Leo coming into a good position in the southeastern sky. Using the map on 169 of our guide book, I was able to pinpoint the fairly bright star gamma Leonis (or Algieba, in Arabic parlance) and after centring the star in the 28x field, I one again cranked up the power to 70x and was delighted to see that, like Castor A and B, it too was duplicitous. The brighter member (primary) shines with a golden countenance, while the secondary component appears yellow−green to my eye in this telescope. They are exceptionally handsome in the instrument at 210x. The system lies about 110 light years away and our guide book informs us that they orbit their common centre of gravity in just over 500 years!


I made a sketch of this system too in the high power field of the 3 inch reflector, pictured below.

An elegant communion of suns, courtesy of your Creator.

















Perhaps you noticed that in the high power field of 210x, both Castor A & B and Gamma Leonis appear to be separated by about the same angular distance. Just how close they are will be the subject matter of my next discussion.

See you soon.

Date: February 23 2018

Time: 14:00 UT

A word on the stellar magnitude scale: The stars in our guide book are divided up on a scale of magnitude, first devised by the 2nd century BC Greek astronomer, Hipparchus. He found it convenient to divide up the glory of the stars into six magnitudes, ranging from the brighest stars (magnitude 1) down to the faintest (magnitude 6) stars that could be seen with the naked eye. This rather arbitray assignment of brightness was improved on in the middle of 19th century of the common era, when the English astronomer, Normon Pogson, defined magnitude 1 stars as being precisely 100 times brighter than those of magnitude 6. Roughly speaking, a first magnitude star will be about 2.5 times brighter than a 2nd magnitude star, and these in turn are 2.5 times brighter than stars of the third magnitude, and so on. On this scale, there are stars that are actually brighter than magnitude 1 and are assigned either magnitude zero or a number less than zero. For example, the brightest star in all the heavens is Sirius, shining with a brightness of −1.46! This scale has the advantage of being able to be extended in both directions; brighter objects take on a greater negative magnitude, while stars fainter than magnitude 6 are assigned brightnesses with greater positive values. In this scheme of things, the Sun shines with a dazzling brightness of −26.7! Our guide book depicts stars of varying brightness with different sizes, going from the largest (brightest) to the smallest(faintest).

Angular measurement as it applies to double stars: As mentioned yesterday evening, the Orion Spaceprobe 3 showed us stars that were separated by various amounts of dark space. To see how close these separations are we must first take note of how angles are measured in astronomy. Recall the full Moon in the sky. This conspicuous orb subtends an angle of 0.5 degrees, but when we spied the small list of double stars discussed above, the telescope was able to resolve things separated by much smaller angles. For convenience, one angular degree is further divided into 60 arc minutes, so using this scale, the full Moon spans 30 arc minutes. One arc minute is depicted as 1′. Now each arc minute, in turn, is further divided into 60 arc seconds (depicted as 60″).

So 1.0 degree = 60′ = 3600″.

Using this new scale, we can begin to explore how much the stars in the above sketches are separated by. The companion to Mizar, for example  is separated from its primary by 14″, but the two tightest pairs thus far examined; Gamma Leonis and Castor A & B have much smaller separations; of the order of just 4″ or so. But just how much finer can our little telescope resolve? For double stars, we have a well established rule of thumb devised by the Victorian mateur astronomer, William Rutter Dawes, who suggested that the the limit is given by the simpe formula called the Dawes Limit: 4.56/ D where D is the aperture of the telescope in inches. Thus, for the 3 inch SpaceProbe, we ought to be able to resolve pairs separted by as little as 4.56/3 = 1.5″. The reader will note that as the diameter of the telescope is increased so does its resolving power. A 6 inch aperture ought to resolve pairs roughly half as small again.

There are a few qualifications we have to make with this formula. For one thing, Dawes devised it for two 6th magnitude stars of equal brightness. Things get more difficult as the brighness difference between the components becomes greater. Simply put, the greater the difference in brightness, the greater the angular separation needed to resolve them. What is more, if the stars are blue and equally faint, separations a little smaller than 1.5″ becomes possible. What’s more, the small obstruction made by the telescope’s secondary mirror (which we learn is just 19.9mm as stated on page 8 of the telescope instruction manual) also tends the shift the maximum resolving power a little upwards to more than 1.5″. Finally, these considerations are strictly true only for resolving stellar targets; as we shall see, the telescope will be able to resolve considearbly finer details on extended objects like the Moon and planets.

Small telescopes such as the Orion SpaceProbe 3(laevo) and the Shortube 80 make dapper double star ‘scopes.


















These qualifications will help us to gauge how well the little reflector will do in due course. But for now, we have more double stars to visit

A Brief Aside: Return to the Moon

Time: 19:30UT

The Moon is now at first quarter and very high up in the southern sky. This is an ideal opportunity to see just how well the little Orion SpaceProbe 3 can perform. After examining its surface at 28x and 70x, feel free to crank up the power to 150x or 210x and note how well the image bears up. Right now you will see amazing details in the crater fields, the Apennine Mountain range and much much more. It’s at times like this that you will come to appreciate just how good this telescope is. Enjoy the ride!

Date: February 24 2018

Temperature: 0C

Time: 21:45UT

It was a beautiful bright day here in the glen but it remains unusually cold. After a very hazy night last night, transparency improved a great deal today and I set up the little telescope at sunset to enjoy wonderful details on the brightening Moon. Seeing remained exceptionally good, as evidenced by very steady high power views of the Moon and double stars using a couple of  larger telescopes I had also deployed to make the most of the unusually good conditions.

Beginning at about 6:45pm local time, I began to make observations of three rather delicate stellar systems; Rigel (Beta Orionis) easily seen as the exceptionally bright white star in the extreme southwest of the constellation. The SpaceProbe showed its very faint companion just off to the southsouthwest of the primary. Although I caught a glimpse of it at 70x using the 10mm Explorer II eyepiece, I elected to boost the power to 158x using my 2.25x Barlow lens  and was rewarded with an even better view. Although Rigel B is situated about 9″ away from its primary, the enormous brightness differential makes it far more challenging than it looks on paper.

Immediately after that, I moved the telescope east into Monoceros (featured on page 187 of our guide book) by using Orion’s downward sloping belt stars as a pointer. I quickly centred Beta Monocerotis in the low power eyepiece. Then I switched to 210x by inserting the 10mm ocular with my 3x Barlow and was rewarded by a wonderful sight. Here is a magnificent triple star system (sketched below). The reader will note that the B and C components of this system are just 2.9″ apart, so significantly finer than anything we’ve thus far explored. Another triple system can be found in Cassiopeia (see the map on page 109). You can find it by making an imaginary line from Ruchbah through Eta and extending that line about the same distance again until you come to a creamy white magnitude +4.6 star, Iota Cassiopeiae. Using a power of 210x, the 3″ SpaceProbe  showed me an even more beautiful and delicate arrangement of three stars. The C component is easier to see owing to its greater distance from A but the B component is also just under 3″ from the latter.

Below are some simple sketches I made for clarity.

Observations of delicate multiple stars as seen with the 3″ Orion SpaceProbe on the fine evening of Saturday, February 24 2018.

















You can take it from me that these systems are challenging for obervers with significantly larger ‘scopes, so I hope you will agree that the 3″ Spaceprobe is a most capable high resolution instrument.

Date: February 26 2018

Time: 00:10UT

Just as I was about to pack up my 8 inch and 3 inch Newtonians at the end of an excellent vigil under the stars at 23:30UT on Saturday, February 25, I spied a couple of stars in Ursa Major, now very high up in the south southeastern sky, indicated by the position of the pencil tip in the image below (page 251 of our guide book).

On the march.

















Specifically, I went in search of a star called Xi Ursae Majoris, also known by the rather charming appellation of Alula Australis. After centring the star in the low power 28x eyepiece, I once again cranked up the magnification on the 3 inch SpaceProbe to 210x, carefully focused and was rewarded with a beautiful, sharp image of a pair of yellow suns, the primary shining at magnitude 4.3 and the secondary, just a half a magnitude fainter at magnitude + 4.8. What is MOST interesting about this system is that they are currently separated by just 2″, so we’re getting awfully close to the double star resolving limit of a 3 inch (76mm) telescope. This pair of stars move fairly rapidly, completing one orbit of their centre of gravity in just under 60 years! The reader will also note that this was the first visual double to have its orbit calculated by Felix Savary back in 1828.

I made a sketch (below) of what I saw in the SpaceProbe. The stars are orientated roughly north to south.

Xi Ursae Majoris; testing the mettle of the little long focus Newtonian.

















Date: February 27 2018

Time: 00:05UT

Temperature: −2C

Seeing: Remaining very good, very bright waxing gibbous Moon, virtually cloudless sky.

We are stuck in very cold, Arctic−like weather which meteorologists have dubbed, “the beast from the east” lol. At this late hour, the eastern sky is now showing the wonderful Spring constellation of Bootes. This constellation is home to a veritable treasure trove of interesting double stars. The other night, I got my first gander through my larger 130mm f/5 Newtonian of one of my all time favourite colour constrast double stars; Epsilon Bootis, or Izar, discussed on pages 90 though 92 in our guide book. Despite the presence of a very bright gibbous Moon, its shines fairly prominently at magnitude + 2.5, so is easy to find even from an urban location.

Bootes is home to some fine double stars, choicest among them being Izar, indicated by the pencil tip in the map on page 91 of our guide book.


















Shortly after midnight local time, it had a reached a decent altitude above the eastern horizon, so I decided to investigate what was what with the 3 inch telescope. In the low power (28x) field, the star looks singular with a comely orange hue. But when I increased the power to 210x, I was once again delighted to see its greenish companion fairly effortlessly in the fine winter air. Now, while the pair is separated by about 3″, there is a fairly large difference in brightness between the components; the primary being +2.6 and the secondary only +4.8. Thus, there is a 2.2 magnitude differential between the components,  making it more challenging than it looks on paper. The Orion SpaceProbe is turning out to be a most excellent double star telescope that even veteran observers will appreciate!

I made a drawing of what I saw in the eyepiece for reference (shown below).

My sketch of Epsilon Bootis in the high power field of the Orion SpaceProbe 3 telescope.











Date: February 28 2018

Time: 17:45 UT


















The beast fae the east is here the noo. Shockeroonie!

The elements are arrayed against us.

Cannae see heehaw, ken.

Date: March 1 2018

Time: 14:15 UT

We endured freezing, blizzard conditions (the worst in the country) throughout last night, bringing at least 30cm of snow. The high winds have created dangerous drifts of fine, powdery snow, making the roads all but impossible to travel on. But we have a warm fire, plenty of food and water, and our spirits remain high.

Small telescopes are very popular choices for observing the Sun, the star that sustains all life on Earth. I thought about how I might use the SpaceProbe 3 to do some solar observing when Spring properly arrives. Two methods came to mind: the projection technique and the use of a white light solar filter. The former involves pointing the telescope, fitted with an eyepiece, at the Sun and using some white card to project a focused image of the solar disk in order that I could record the presence of sunspots(regions of high magnetic intensity on the surface of the Sun). But I didn’t want to risk damaging the telescope with excess reflected heat (even a small aperture telescope like this can generate dangerous levels of heat), so I thought about using a white light solar filter as an alternative strategy.

Since I already owned and use an inexpensive white light solar filter with my Shorttube 80 achromat, I wondered whether or not it would fit onto the Spacerobe 3 optical tube.

The white light solar filter used with my Short tube 80 achromat fits snugly on the SpaceProbe 3 telescope!

















Well, it was like finding money in the pocket of an old jacket lol! The filter fitted snuggly over the front of the instrument! It was the perfect fit! Now I can observe the glory of our star in perfect safety. The tall tripod upon which the telescope sits is a good height off the ground, allowing any ground thermals to be kept at bay. This should make an excellent little solar telescope but I shall have to wait until this severe weather leaves our shores before more testing can be done.

The filter works by rejecting 99.999 per cent of the incident solar radiation, passing only a tiny fraction of the Sun’s light to the eye.

That being said, it is of paramount importance that the reader heed this warning:


Date: March 2 2018

Time: 13:15 UT

If you plan to use the SpaceProbe 3 to observe the Sun on a regular baisis, it pays to remember that the most economical way of acquiring a solar filter is to make one yourself. There are many outlets that sell various kinds of polymers specifically designed to reject the vast majority of the Sun’s light and heat. Perhaps the best of all is the very well established Astrosolar Material, marketed by Baader Planetarium. You can purchase a sheath of this material for under £20 UK and use it to make your own, homemade filter. Here is a link to one such DIY project.


A Request:

Attention Experienced Telescopists!

I’d appreciate if someone were to follow up on the reports thus far communicated. It’ll take up a little bit of your free time, but I think you’d get a kick out of it.


Date: March 7 2018

Time: 15:20UT

Sol seeker.

















Well, after a week long hiatus owing to terrible winter weather, the Sun briefly poked its brilliant rays through the clouds and I was finally able to see if the solar filter worked as advertised. I can report that the Spaceprobe 3 did an admiral job of focusing the solar disk sharply using the 10mm Explorer II eyepiece. Because the Sun’s disk is precisely the same size as the full Moon, it takes up the same area of the field.The reader will note that the small finder ‘scope objective was covered during the observation, so as to prevent any potential accidents! See, you have to think ahead when observing our star!


Was there anything to see?

No! Lol!

Though I’m certainly not a diehard solar observer, I’ve never seen it so completely devoid of sunspots! That’s not to say that there are no sunspots on its surface only that they were beyond the detection limits of this small telescope on this occasion. That having been said, there is no reason why a would−be user of the Orion Spaceprobe 3 could not use this as a very effective white light solar telescope; adding to the versatility of the instrument.

Curiously, low sunspot activity is somewhat correlated with cold spells, so in a way, this was not completely unexpected.

Taking stock: By now, I’ve demonstrated just a tiny number of things in the heavens that are accessible to this excellent little telescope. And the sky’s really the limit! By studying the constelattions that are well placed in your local skies, you could spend many happy months and years exploring a host of other deep sky objects, as well as the glories of the Moon and never once feel you’re missing anything. And once you’re done, you can always visit them all over again, each in its proper season. Soon, you’ll find that they become old friends! Such is the atitude of a determined telescopist!

I would like to end this blog by exploring something completely different; a planet dwarfing the Earth in size and majesty, hurtling ’round the Sun beyond the snowline of the solar system. I speak of none other than mighty Jupiter. More on this soon.


A Brief Daylight Experiment

Comparing the image sharpness and light gathering power of the Orion SpaceProbe 3 with a stopped down 90mm f/5.5 ED apochromat.

Introduction: On Sunday afternoon, I set up both the Orion SpaceProbe 3 f/9.2 Newtonian alongside a high quality 90mm ED f/5.5 apochromatic refractor during a bright spell in order to estimate the light gathering power of the Newtonian and also to compare and contrast image sharpness in both instruments. Both telescopes were kept out of direct sunlight, so as to miminise thermal effects.

Materials and Methods: I constructed three aperture masks of progressively larger aperture from cardboard. These had diameters of 56mm, 65mm and 73mm, respectively. The masks were affixed using parcel tape, placed ahead of the dew shield of the refractor and carefully centred on the optical train. Starting with the 56mm aperture mask, I compared the images of the denuded branches of a horse chestnut tree about 100 yards in the distance in both telescopes. I charged the ED refractor with a Vixen HR 2.4mm ocular delivering 208x diameters. A 2” Tele Vue Everbrite diagonal (99% reflectivity) was used to maximise image brightness in the refractor. The Orion SpaceProbe 3 reflector was charged with a 7.5mm Parks Gold coupled to a 2.25x Barlow delivering 210x.  The experiment was repeated using the 65mm and 73mm aperture masks on the refractor and the views similarly compared. My wife also volunteered to assess the images and our findings were in good agreement.

Making the aperture masks: left to right: 56mm, 65mm and 73mm, respectively.


Results: There was a clear and unequivocal difference between the images when the refractor was fitted with the 56mm aperture mask. The SpaceProbe 3 delivered a noticeably brighter image but image sharpness was quite comparable.

The masks are easily affixed to the front of the refractor using parcel tape.

















Using the 65mm aperture mask, the results were much more comparable, with the refractor yielding a slightly brighter image but image sharpness was still quite comparable. Finally, when the 73mm aperture mask was affixed, the refractor produced the brighter image although image sharpness remained quite comparable.

Locked on a stationary target.
















The Vixen HR 2.4mm ocular with a 2″ Tele Vue Everbrite diagonal.



Conclusions: The 76mm SpaceProbe reflector has a light gathering power equivalent to a high quality quality 60 to 65mm refractor. Image sharpness is right up there with the apochromat in these daylight tests. That’s a very good result for a telescope that retails for less than £70 delivered to your door. In comparison, a top quality 60 to 65mm Apo (without a diagonal, eyepieces or mount) could set you back between £400 and £800!

Final note: We sent our results to former Sky & Telescope Associate Editor, Tony Flanders, whose opinion I trust, and who has also evaluated the Orion Space Probe 3 in a past review. He agreed with our assessment.

Some readers may legitimately ask why a 76mm reflector would not be as good as the equivalent sized refractor. The answer lies in the way these telescopes are designed. The refractor uses a lens to collect light and its transmission is very efficient. Mirrors are not quite as good though, since they reflect a high percentage of the light which strikes them, though not all. For example, if the mirrors both reflect say, 85 per cent of light incident upon them, then the percentage of light that reaches the eye will only be 85 per cent of 85 per cent; that is 72 per cent. Add in the small amount of light lost by the obstructing effect of the secondary mirror and you can begin to appreciate why it is not as efficient as the same size refractor. Having said all that, the little reflector still collects enough light for you to enjoy many objects in the heavens, as we have discovered.

Date: April 1 2018

Time: 20:45 UT

Temperature: 0C

Conditions: Good clear sky, no wind, steady conditions.


An Encounter with Venus

It remains unseasonably cold. Indeed, more snow is forecast for tomorrow. I can’t help but think that this is in part attributed to the solar sunspot minimum that is upon us just now. Nevertheless, the light on the landscape and the lengthening days inform me that April is truly here, lol.

At dusk, I set up the little Orion SpaceProbe 3 reflector at the side of the house to observe Venus, which appeared like an intensely bright star sinking into the western sky. Venus is now an evening ‘star’. Excitedly, I turned the telescope on the planet, charging the instrument with the 10mm Explorer II eyepiece delivering 70 diameters. Well, the strongly gibbous disk of the planet was clearly visible, but it was completely featureless. Increasing the power to 140x didn’t really help things all that much. You see, you can discern very little on the Cytherean disk in any telescope, however large and powerful. But what I could see was the six diffraction spikes emanating outward from the brilliant white planet. I found these very striking and quite beautiful to behold. As mentioned previously, this six−pronged diffraction spike is produced as a consequence of the secondary mirrors three spider vanes. In contrast, the view in my larger Newtonians shows cruciform diffraction spikes owing to the four spider vanes supporting their secondary mirrors.

At present, Venus is at its smallest; just 10 arc seconds in size. It is much larger when it is in its crescent phase and slowly shrinks as more and more of the disk is revealed. Venus, like our Moon, goes through phases!

Venus is covered in quite good detail on pages 348 through 352 of our guide book. And though it looks serene through the telescope, you wouldn’t want to be there. Indeed, it is the nearest thing to a proverbial hell that humans could possibly imagine. Its choking atmosphere of carbon dioxide has generated a massive, run−away greenhouse effect that has raised the temperatures on the surface to about 470C; so hotter than any domestic oven! The atmosphere exerts a pressure in excess of 90 times that found on the Earth at sea level, and then, to add insult to injury, the clouds are not made of cooling water vapour as they are on our world, but instead are composed of droplets of sulphuric acid with a concentration of about 80 per cent. Anyone standing on its surface would be simultaneously crushed, choked, incinerated and corroded to death! Not a pleasant prospect methinks.

But Venus was not created for life, whereas the Earth was.

Thank goodness for small mercies!

I made a drawing of what I saw at the telescope.

Venus as seen through the 3 inch SpaceProbe Newtonian on the evening of April 1 2018.















An Encounter with Jupiter:

Studying Jupiter from the guide book.

















Date: April 28 2018

Time: 01:30am

Temperature: 3C

Conditions: mostly clear, bright gibbous Moon now sinking into the southwestern sky, rather cool.

This morning, I enjoyed my very first telescopic observation of the giant planet Jupiter in 2018 as it approached the meridian. I very much wanted to begin this season of observations using the Orion SpaceProbe 3 reflector. And boy was I not disappointed! To see it well, I had to move the telescope(on its mount) across the road to the children’s play park so that I could get a good view of the planet as it hung over the trees like a distant coach lamp. But that was never an issue, as the set up is so lightweight that transporting it over the 80 yards of so was not an issue.

Charging the telescope with the 10mm Explorer II eyepiece, the telescope delivered an excellent panoramic view of the planet at 70x with its four large satellites; Io, Europa, Ganymede and Callisto. Even at this power, I was able to see that the planet was flattened at its poles. This is caused by the planet’s rapid rotation on its axis, taking less than 10 hours to complete one revolution. As a result, its equator bulges owing to fierce centrifugal forces, which also somewhat flattens the poles. Jupiter’s shape is thus best described as an oblate spheroid.

Using the 2.25x Barlow with the 10mm eyepiece yielded a power of 158x, but while this gave a sharp image, I found that a better image was obtained by backing down on the magnification in order to optimise resolution, contrast and image scale. I reached for my 1.6x Barlow with the 10mm Explorer giving a power of 112x. This  gave a wondeful image! I was able to make out the tan coloured equatorial belts and also a few other belts at more northerly and southern latitudes (maybe 5 bands in all?). I could also make out significant detail within the equatorial belts. Studying the image from minute to minute, I tracked the planet simply by nudging the telescope along, applying gentle, finger pressure to the optical tube.

Having observed and enjoyed the Giant Planet in many small telescopes over the years, I can report that the 3″ f/9.2 Newtonian provided an image that was significantlty more detailed than a classic, long focus 60mm refractor and was more reminiscent of the details garnered by a very high quality 66mm William Optics triplet apochromatic refractor I had the pleasure of owning many years ago. The SpaceProbe 3 will definitely allow you to study this planet, and with some practice, you will be able to make out other features, such as the famous Great Red Spot(GRS), an enormous, terracotta brick−coloured storm that has persisted on the planet for at least the last few centuries. Such tempests last much longer on this world owing to its lack of a solid surface, which causes terrestrial storms to abate quickly as they get drained of energy when they fall over land. Every now and then (but not on this occasion), one or more of the satellites crosses in front of the planet allowing you to see a disk shaped shadow of the same moon projected onto the cloud tops of this giant world. When you see such an event, it will most assuredly take your breath away!

A light blue Wratten no 82 filter is a good tool to enhance belt detail on Jupiter.

















I watched the planet until it culminated in the south after 2:00 am local time, when it reached the same altitude as Rigel (so not very high) does in my local skies, and was delighted by the high quality images this simple, inexpensive telescope served up. As an experiment, I screwed on a light blue Wratten filter to the same eyepiece/Barlow combination and found that this filter improved the contrast between the dark belts and brighter zones of Jovian atmosphere. I would advise other observers to try this filter (which can be picked up for just a few pounds).The planetary image in the telescope was quite stable and relatively devoid of turbulence in comparison to larger aperture instruments. That’s because small aperture ‘scopes such as the SpaceProbe 3 are relatively insensitive to the vagaries of the atmosphere and are quite well suited to low altitude planetary observations.

I left the field tired but genuinely impressed with how well the telescope showed this fascinating target. I even made a quick sketch of the panormaic view at 70x but hope to make a full disk drawing of Jupiter in due course.

You can find out much more about Jupiter and its satellite system by consulting pages 362 through 367 of our guide book.

The mighty planet Jupiter, as it appeared in the Orion Spaceprobe 3 telescope in the wee small hours of April 28 2018.


Date: May 19 2018

Time: 23:45UT

This evening I set up the Orion Spaceprobe 3 reflector to have a look at Jupiter and was delighted to see that the Great Red Spot was prominent near the central meridian (the planet’s north−south line). I made a quick sketch (shown below) of what I saw using the 10mm Explorer II ocular supplied with the telescope coupled to a 1.6x Barlow yielding a power of 112x and a Wratten no 82A light blue filter. Having a hoot with this charming little telescope!

Jupiter with its main belts and zones and the Great Red Spot(GRS) near the planet’s central meridian, as seen through the 76mm f/9.2 Orion Spaceprobe reflector. Local time: 23:4o UT.






Spotting the GRS proved rather easy for this telescope even without the filter, its distinctive colour being readily detected.This is an instrument that will certainly allow you to study the constantly changing aspects of this fascinating world. And with more practice, you will become adept at recording its subtle features.


Three cheers for Oona.

















We have now come to the end of this journey with the Orion Spaceprobe 3 altazimuth reflector. As I’ve demonstrated, you can accomplish a great deal with the instrument on the Moon, bright planets, the Sun and into the depths of the deep sky. I feel very privileged to have acquired this simple little telescope and it will remain in my stable.

I hope you have enjoyed this blog.

Keep looking up!


Neil English is author of several books on amateur telescopes.


De Fideli.

‘Scope Testing: What the MTF Graphs Reveal.

MTF graph comparing a perfect 5 inch triplet Apo(blue line) with that of an 8 inch Newtonian with a 24 per cent obstruction(worst case scenario)  shown with a dotted red line, as well as a sensibly perfect 8 inch Newtonian(<20% obstruction) shown as a solid red line). Image credit: Ed Moreno.





Over the last few years, I’ve been conducting extensive field tests comparing Newtonian reflectors to refractors. Those conclusions can be found elsewhere on my website for both my 130mm and 203mm reflectors and a variety of refractors from 90mm to 160mm in aperture. In this blog, we’ll explore what Modulation Transfer Function(MTF) graphs have to say about the conclusions reached.


Tune in soon for more details……..


De Fideli.

Winds of Change: Some Comments on the SkyWatcher Evostar 72EDS Pro Refractor

Breaking the mould; the SkyWatcher Evostar 72EDS Pro.



For a good few years now, SkyWatcher has brought many quality telescopes to market at very reasonable prices. One of the major reasons for this success is the company’s  investment in better manufacturing technology, as well as improvements in quality control. This author can personally vouch for the fine Newtonian and Maksutov Cassegrain telescopes that are now available at prices that won’t break the bank. Apochromatic refractors have remained noticeably more expensive though, and while the same company has offered both doublet and triplet models at prices that are among the lowest in the market, I felt they still remained on the expensive side, especially when one considers their rather small aperture for purely visual use. Their relative expense still registers somewhat as an anomaly to my mind. Why, pray tell, should they command such high prices relative to other kinds of telescopes? That said, recently, SkyWatcher has marketed a few products that are significantly less expensive than even their earlier offerings; and one of them piqued my attention; the SkyWatcher Evostar 72EDS Pro Refractor.

So what does your £265 buy? Well, as it turns out; quite a bit! The telescope has a two speed Crayford focuser that can be locked for astroimaging applications, and it can also accommodate both 1.25 and 2 inch accessories, including diagonals and eyepieces. The machined aluminium dust cap screws on to the dew shield; a very nice touch!. It comes with dedicated tube rings and a universal dovetail plate for easy securing on a variety of light weight mounts. The optical tube is typical SkyWatcher, not overly showy and more practical than overtly ornate. While nearly all other similarly sized instruments come with a retractable dew shields, the Evostar 72EDS is of fixed length but is easily removed for transport. And you even get a nice custom fitted travel case for easy storage and transport. It also has a bracket for mounting a suitably sized finder ‘scope. Check out this youtube video for more details of what the package provides.

In a departure from previous marketing strategies, SkyWatcher has not disclosed the nature of the ED element their optical engineers have mated to the Schott glass crown lens of this 72mm ED doublet, but early indications are that it offers very good colour correction for its attractive price tag. All of this is very good news for the consumer, as it appears SkyWatcher is listening to their customers and bringing to market more economical ED refractors that offer significantly better overall value.

That said, considering the many nice mechanical features this new refractor offers, I wonder what percentage of the total cost of the telescope is divested to the objective? Are ED objectives really that expensive to manufacture? Judging by the modest cost of the entire package, the answer must surely be “relatively easy.”

In comparison to other models recently launched by companies like William Optics, who now offer a 61mm ED doublet for £400 UK, the new SkyWatcher will almost certainly be of greater utility owing to its significantly larger aperture (for many seasoned observers 61mm is just too small). This is especially the case for those amateurs who do not dabble in astrophotography.

I am personally comfortable about endorsing this product and see it as a significant and welcome move in the right direction for money conscious hobbyists. Will I be making a purchase myself? No, as I already have too many telescopes and, as I’ve already disclosed, I do virtually all my observing with modified SkyWatcher Newtonians which offer superior daylight and nighttime views to any small refractor in this aperture class. But I do think more folk can now enjoy the considerable charms of a small, short, high quality refractor.

The move by SkyWatcher will hopefully be part of a much greater impetus to drive down prices for apochromatic refractors generally. The hobby can only grow if more amateurs have access to decently priced products, and in making this move, SkyWatcher will surely impose pressure on other makers to offer their wares at fairer prices. The soon to be introduced ED 150 by the same company promises to continue this trend and I commend SkyWatcher for embarking on this very encouraging (and profitable) venture.


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



De Fideli.

A Newtonian Travel ‘Scope

Wednesday, February 3 2016: SkyWatcher has established a solid international reputation for producing high quality Newtonian optics for the modern amateur astronomer, and at prices that won’t break the bank. Having been thoroughly satisfied with a 8″ f/6 Skyliner Dob, I became very curious about a smaller, model – the Heritage 130P (a 5.1″ f/5 Newtonian with a parabolic primary) tabletop Dobsonian – which promises to provide decent light grasp and resolution in an ultra-portable package for take anywhere travel and short grab ‘n’ go excursions to the back garden.

The telescope was purchased new from Rother Valley Optics on Tuesday morning, February 2, and arrived in the mid-afternoon today. The price, inclusive of postage, was £129.

The telescope came double-boxed and involved no assembly. The optics looked clean and streak-free. A neat instruction manual accompanied the instrument.

The Heritage 130P Dobsonian as received.

The Heritage 130P Dobsonian as received.











The ‘scope, weighing about 6 kilos with the mount, has a built-in carrying handle for swift transport into and out of the house.

Following along the same lines as their extremely successful flextube line of larger Dobs, the Heritage 130P can be extended to reveal the upper tube assembly, lengthening the tube from just 38cm to about 61cm. The lower assembly is adorned with the names of time-honoured astronomers, celebrating four centuries of telescopic astronomy. While some folk might find this ‘tacky,’ I rather liked it.

The Heritage 130P fully extended.

The Heritage 130P fully extended.










Remarkably, the telescope was almost perfectly collimated out of the box, as evidenced by the just slightly offset red dot from the centre-marked spot on the primary mirror. That’s a nice touch, as one can imagine the reaction of a complete novice were he/she to discover that the optics were delivering iffy views as a result of mis-aligned optical components. It might be enough to put someone off the hobby for good.

Note the position of the red dot from the laser collimator; just a shade out of whack.

Note the position of the red dot from the laser collimator; just a shade out of whack.

Once the collimation was tweaked, I investigated retracting and extending the tube assembly several times to investigate the rigidity of the structure. I am pleased to report that the collimation held quite well but might still require last-minute tweaking for more demanding tasks, such as obtaining the best lunar and planetary views, as well as double star work. Overall though, this is a very well thought out piece of kit and certainly better than I had anticipated.





The telescope primary and secondary mirrors are fully adjustable and can be aligned in a matter of minutes. Unlike the three ultra-thin spider vanes on larger models, the secondary mirror on the Heritage 130P is affixed to a single vane, which is a good bit thicker than the latter; a necessary design compromise to maintain that little bit more stability to the optical train.

The adjustment screws behind the f/5 parabolic primary mirror.

The adjustment screws behind the f/5 parabolic primary mirror.

The secondary support is of high quality and is easily adjustable with a user supplied hex wrench.

The secondary support is of high quality and is easily adjustable with a user supplied hex wrench.




















The focuser is unusual. Unlike standard rack and pinion or Crayford type focusing mechanisms, the Heritage 130P employs a simple helical focuser which involves rotating the eyepiece either clockwise or ant-clockwise to bring objects to a sharp focus. In addition, the length of the upper tube can also be adjusted to accommodate cameras and other equipment. In short, any eyepiece will reach focus using a combination of these procedures. Only 1.25″ oculars can be used with the instrument, however.

The unusual helical focuser on the Heritage 130P Dobsonian.

The unusual helical focuser on the Heritage 130P Dobsonian.











Some observers may find reaching precise focus a little fiddly, but with a bit of practice, it works smoothly and accurately.

The Heritage 130P also came with a simple red dot finder (RDF) to aid in locating objects quickly under a dark sky.

The basic but useable red dot finder is easily attached to the upper tube assembly with a small screw driver.

The basic but useable red dot finder is easily affixed to the upper tube assembly with a small screw driver.

A particularly attractive feature of the instrument as received is the dovetail mounting of the optical tube assembly which enables one to remove the tube assembly from the mount proper for even easier storage.

The optical tube can be removed from the mount if necessary to aid storage/transportation.

The optical tube can be removed from the mount if necessary to aid storage/transportation.

In addition, the dovetail plate allows the user to mount the instrument separately on other types of mounts such as this author’s ergonomical Vixen Porta II alt-azimuth for an alternative style of observing. What a nice touch!

The SkyWatcher Heritage 130P mounted on the author's Vixen Porta II alt-azimuth mount; a particularly stable configuration.

The SkyWatcher Heritage 130P mounted on the author’s Vixen Porta II alt-azimuth mount; a particularly stable configuration.























Optical testing: Although the instrument suffers from the introduction of considerable amounts of stray light during daylight use without employing some sort of light shroud, I set the instrument up in the late afternoon, aiming the instrument at a roof top about 100 yards distant. I didn’t wait around to use the supplied oculars (which are adequate but not great for testing) but instead decided to push the ‘scope as hard as I could. To that end, I ran inside and affixed a good quality 6mm orthoscopic to a 2.25x Baader shorty Barlow lens, which would deliver a power of 244 diameters. Inserting these into the helical focuser, I carefully rotated it until best focus was achieved. Although the view was a bit drowned out with extraneous light, I am happy to report that the image of the terracotta roof tiles came into very sharp focus; a great initial sign that the optics were of potentially high quality.

After dark, more cloud encroached, but I waited for the odd sucker hole and was rewarded by a clear spot corresponding to Auriga, then high in the eastern sky. Relocating the instrument in a dark spot in the garden, I centred the bright star, Capella, using my multi-coated 32mm SkyWatcher Plossl in the field (yielding a true field of 2.5 degrees!) and was delighted to observe (with my eye glasses on)  a beautifully sharp vista, with pinpoint stars across most of the field. Then, I investigated the high power view of Capella at 244x and after refocusing, was thrilled to see a tight white Airy disk with diffraction rings a shade more prominent than what I have observed in my work horse telescope, a larger 8″ f/6 Dobsonian. This could be explained by the larger central obstruction of the Heritage telescope (~29 per cent by aperture) as compared with 22 per cent for the larger 8 inch.

On a whim, I moved the instrument north-eastward from Capella and centred the star, theta Aurigae. Focusing as accurately as I could, I was able to steadily hold its very faint companion at 244x, some 4 arc seconds away from the primary. Very encouraging to say the least!

It wasn’t long before the skies completely clouded over, and the drizzle came back, ending my first light vigil under the stars. Needless to say, the instrument performed surprisingly well under admittedly dodgy observing conditions.

More testing in the pipeline though.

Thursday, February 4, 2016


Having collimated the telescope in situ and placed a makeshift light shround around the upper telescope assembly (UTA), I am happy to reaffirm that the telescope delivers tack sharp images of distant willow tree branches at 244x.

Friday, February 5, 2016

The Heritage 130P has a parabolic primary mirror, that is, it is figured into the shape of a parabola. Why is a parabolic shape responsible for such sharp images in a Newtonian reflector? It’s an interesting question, yet many amateurs accept it as a given. But we can do considerably better than that. We can analyse the properties of the parabola, one of the conic sections beloved to the mathematicians of classical antiquity, and thereby gain a deeper appreciation of why this shape, over all others, is chosen by opticians in the fashioning of high quality primary mirrors. Our analysis will borrow from the approach of the great French mathematician, Rene Descartes (1596-1650), who developed a way of investigating geometry using algebra.

A parabola is the set of all points which are equidistant from a given point called the focus and a given line known as the directrix.

The image below outlines the basic features of a parabola drawn on a x-y axis.

The Parabola

The Parabola










Let the focus be the point S( a,0) and the directrix be the line x=-a, as shown in the diagram. Consider any point on the parabola, P(x,y).

Thus, by definition, the length of SP = length of PM

So [(x-a)^2 + y^2]^0.5 = x + a

Therefore, (x-a)^2 + y^2 = (x+a)^2

Thus, x^2 -2ax +a^2 + y^2 = x^2 + 2ax + a^2

From which y^2 = 4ax ( Eq 1)

This is the standard form of the equation of a parabola.

Consider next the parametric equations x = at^2 and y = 2at.

Substituting the expression for x into equation 1 we obtain;

y^2 = 4a^2t^2 = 4a(at^2) = 4ax

So, x = at^2 and y = 2at represents the parametric coordinates of any point on the parabola y^2 = 4ax.

We can use this to derive two more equations that will enable us to arrive at the result we want. Consider the diagram drawn below.

The parabola with the point P defined parametrically.

The parabola with the point P defined parametrically.









y^2 = 4ax

Differentiating implicitly with respect to x we obtain;

2yf'(x) =4a

so f'(x) = 2a/y, which is the gradient of the tangent at any point.

Now since y = 2at, the gradient becomes 2a/2at = 1/t

And so the equation of the tangent to the parabola at the point P is given by:

y – 2at = 1/t(x-at^2)

Multiplying across by t  gives;

ty – 2at^2 = x-at^2

or  x – ty + at^2 =0 ( Eq 2)

Also, the gradient of the normal at P = -t and so the equation of the normal will be:

y – 2at = -t(x-at^2)

or tx + y – 2at – at^3 = 0 ( Eq 3)

Now we are ready to obtain further information from the parabola under discussion.

Let the tangent at P intersect the x-axis at R and the y-axis at U, and let the normal to the parabola at P intersect the x-axis at V, as shown in the diagram below:

parabola 3

The coordinates of R are obtained by setting y = 0 in equation 2

x – ty + at^2 =0 and so if y = 0 then x = -at^2 and so the coordinates of R are (-at^2, 0)

The coordinates of U are obtained from setting x = 0  into equation 2, from which it is easily shown that y = at i.e. U(0, at).

The x-coordinate of V can be obtained by setting y = 0 in equation 3;

tx + y – 2at – at^3 = 0 and when y = 0 we obtain:

t(x- 2a – at^2) =0,and since t cannot equal zero we have

x = 2a + at^2 and so the coordinates of V are given by (2a + at, 0).

From these results it is possible to verify the following:

(i)  U is the midpoint of PR

(ii)  length of SR = length of SV = length of SP

(iii) US is parallel with PV and that PU is perpendicular with SU

I will leave these as exercises for the interested reader.

Now, to the meat of the analysis. Consider a line PZ drawn parallel to the axis of the parabola as shown in the diagram below:

parabola 4



Since  length SP = length SV so too must angle SPV = angle SVP

But angle SVP = angle VPZ since PZ is parallel with RV

So angle SPV = angle VPZ

But ZPV is the angle of incidence of a ray of light incident upon a reflective parabolic surface and so the law of reflection requires that the angle of reflection be the same i.e. angle VPS.

But since P is independent of S, the result implies that any ray of light parallel to the axis will be reflected through the focus, S.

This is the reason why parabolic mirrors work so well, as they completely avoid a phenomenon known as spherical aberration, which can can plague other kinds of optical designs.

That’s enough math for one evening eh.

After a day of more or less constant rain, the sky appears to be clearing up and so I’ll get some more time under the starry heavens using my little parabolic Newtonian.

Thank goodness for small mercies!

Saturday, February 6 2016

Time: 00:05h

The telescope was collimated perfectly before use and left to cool in a dry, unheated shed. Initially, I had intended to use my Baader zoom and dedicated 2.25x Barlow to observe Jupiter, now 31 degrees above the horizon. To my chagrin, I discovered that this combination failed to reach focus. Due to the constant interruptions from clouds and with the rain never far away, I did not want to retract the UTA enough to get it to focus. Instead I chose a 7.5mm Parks Gold ocular and 2.25x Barlow yielding 195x.

Though the helical focuser is a bit fiddly and takes some getting used to, I am happy to report that the Jupiter images were wonderful in this telescope, with lots of nice detail showing up under moderate scrutiny. The planet’s enormous equatorial belts were seen in their faithful colours and many shades of tan were observed. A Baader Neodymium filter took away a little bit of glare surrounding the planet, helping to bring out more subtle details. Although I felt 195x was a little too high, and would have been happier with 160x, I was most impressed by what this inexpensive Newtonian was delivering.

Jupiter as seen through the Skywatcher Heritage 130P Dobsonian at midnight of February 6.

Jupiter as seen through the Skywatcher Heritage 130P Dobsonian at midnight of February 6.

Turning then to some brighter stars appearing from behind the clouds, I was equally impressed by how well the instrument focused them down to tight round Airy disks at the highest powers pressed into service (244x). The telescope seems quite immune to atmospheric turbulence as judged by the calmness of the images. Returning to a 32mm Plossl, I enjoyed a spell binding few minutes drinking up the famous Double Cluster (Caldwell 14) in Perseus. The 20x delivered by this eyepiece provided a very generous field of view, allowing both star clusters to be easily framed in a most beautiful portal.

This is certainly not a toy telescope! It is impressively powerful with high quality optics. Indeed my initial impressions were very similar to this assessment made by Ralph Bell back in 2009.

Monday, February 8 2016

Time: 18:30-45 UT

I enjoyed another brief vigil under the stars with the Heritage 130P Newtonian.  Charging the telescope with a 32mm Plossl (20x), I first visited the Pleiades, now high in the southern sky. Its constituent stellar components focused to fine points of light, pure white as the driven snow, with excellent contrast. Though I did not do a side by side comparison with my 80mm f/5 shorttube refractor, I was immediately aware of the Heritage’s significant advantages in light gathering power, with many more fainter members coming through at a glance. Then, I moved the instrument southwards, where majestic Orion was just about to culminate. The view of M42, the Great Nebula, was a sight for sore eyes. Cranking up the magnification to 81x with my Baader Zoom, I enjoyed a sumptuous field of view dominated by the emission nebula and Trapezium stars at its heart. The hinterland of the nebula was jewel encrusted with brilliant white stars set against a jet black sky.

Before packing up, I examined three higher resolution targets; first Rigel, just a few degrees to the southwest of M42. Using a power of 108 diameters, I was delighted to see the faint companion to this brilliant giant star cleanly and steadily. Then I swung the telescope over to Cassiopeia, now high in the northwestern sky. First I centred eta Cassiopieae and keeping the power at 108x I was able to easily split this pair, consisting of a beautiful yellow primary of magnitude +3.5 and its ochre companion some 13 arc seconds away, shining considerably more faintly at magnitude 7.4. Finally, I moved the Heritage 130P over to iota Cassiopeiae and could make out two of the three components of this system at a glance at 108x. The third member remained somewhat more elusive though, so I attached the Baader 2.25x Barlow yielding a higher magnification of 244x, refocused, and was overjoyed to see all three components clearly and precisely!

The Heritage 130P enjoying a dry afternoon.

The Heritage 130P enjoying a dry afternoon.

The imminent arrival of another student meant that I had to end the short vigil there, but it was very rewarding nonetheless. The telescope has great potential as a deep sky instrument and appears to be no slouch on moderately difficult double stars.

Tuesday, February 9 2016

Time: 19:00-30 UT

After a cool but crisp day, I continued my Newtonian education by fielding two telescopes; the Heritage 130P and a high quality 90mm f/5.5 ED doublet on loan for a a magazine review. Both instruments were given plenty of time to thermally acclimate and placed in the darkest spot in my garden to minimise stray light flooding into the open tubed reflector.

The multicoated objective of the f/5 ED90 'scope.

The multi-coated objective of the f/5.5 ED90 refractor.

The sky after sunset was clear but the stars were corruscating fairly wildly. Transparency was excellent though, so I decided to assess the seeing conditions some more by turning the 130P on Castor, now quite high in the eastern sky. Charging the telescope with a power of 195x, both the A and B components were resolved but there was quite a bit of turbulence which made the stars bloat significantly from their calmer appearances under better seeing conditions.  Comparing the same target in the ED90 charged with a power of 188x, both components were also resolved but there was still noticeable turbulence. It was not quite as unsettled in the refractor though, a consequence I suppose of its smaller aperture. This demonstrated to me that poor seeing can (though thankfully rarely at my location) adversely affect small telescopes. I judged the image in the refractor to be slightly more aesthetically pleasing under these conditions.

The reader will also note that the refractor comes equipped with a state-of-the-art 11:1 dual speed micro-focuser and so was considerably easier to focus finely than with the comparatively crude helical focuser on the Heritage 130P. This may also have contributed to my conclusions regarding Castor A & B. Accurately focusing f/5-ish instruments is never a walk in the park.

Turning to M42 once again, I compared and contrasted the images in both telescopes matching their image scales as best I could (~100x). Both telescopes delivered good images but the superior light gathering power of the reflector gave it a distinct edge. More nebulosity was seen and the stellar images were noticeably brighter in the reflector. This was despite the fact that the refractor had superior contrast, with a blacker sky background.

I am hoping that conditions will improve by the time Jupiter rises in the sky in a few hours from now.

22:45 UT

The sky has completely clouded out and the forecast predicts that it won’t clear again until the wee small hours. I am very tired though, so will leave further testing for another night.

Thursday, February 11 2016

Time: 00:50h

I fielded the same two instruments tonight as last night; the 130P reflector and the ED90 refractor. I finally found a good eyepiece to optimise the 130P’s capabilities on Jupiter; a 4mm Plossl delivering a power of 165x.The ED90 was charged with a power of 150 diameters.

Seeing was only marginally improved over last night (Antoniadi III-IV) but it was nonetheless a good test of what both instruments could deliver on Jupiter under these sub-par conditions (we have a north westerly air flow here which almost invariably brings more turbulent conditions but with excellent transparency).

I fitted a Baader Neodymium filter (with very high light transmission and virtually no colour shift, more a moon and skyglow filter than anything else)  to the 130P to reduce the glare a little.

Comparing the images in both telescopes over a period of about half an hour, I gathered my thoughts.

Both showed some nice details in the equatorial belts. The ED90 image revealed hints of more subtle details at higher and lower latitudes but in the end I felt the 130P showed that little bit more. In particular, it was easier to see those details at temperate latitudes, as well as the more delicate polar shadings. One very striking difference was the colour of the Jovian disk presented in the telescopes. The ED90 was noticeably yellower in overall hue – a consequence of its imperfect achromaticity in comparison to the perfectly achromatic reflector. The latter presented a brighter disk in its true colour; much more creamy white than yellow. The Neodymium filter showed that the colour in the ED90 remained the same but with a little more light loss.

In retrospect, this should not have come as a surprise; while the refractor has a low dispersion element, which improves colour correction, it still can’t deliver perfectly achromatic images. Yes, it’s a sizeable improvement over the traditional achromat but still not perfect. Only a reflector image – which brings all wavelengths of light to the same focus – could really reveal this. In addition, a brighter image can also help the eye see finer details. You need light to see such details.

That being said, I do know the ED90 is capable of showing more on better evenings ( data not communicated) but so must the 130P, as they were both compared under the same conditions. I am eager to conduct further tests in this capacity as soon as the seeing conditions return to normal.

This was an instructive vigil. The 130P should  give very decent images of Jove when the seeing is fair to good.


SkyWatcher has also brought to market a related telescope called the 130PD-S, which, as far as I can tell, features the exact same optics as those possessed by the Heritage 130P but retails for about £30 more. The optics are housed in a closed tube and the spider vanes are akin to what is seen on a traditional Newtonian. It also features a low profile 2-inch dual speed focuser for precise focusing and the secure mating of a CCD camera to the instrument. The 130P-DS has proven a huge hit with astro-imagers who have used it to good effect to capture stunning views of the night sky. Featured on this link is a plethora of deep sky objects captured by this modest telescope, but the reader will also take note of the lunar and planetary images captured by the same instrument.

Although not a visual assessment, I hope you will agree that the unlying camera shows just how good the optics are in these telescopes.

Friday, February 12 2016

Time 00:01UT

The seeing was vastly improved tonight, frosty but no wind. I only had time for one target; Jupiter. Like last night I fielded the same telescopes and employed the same magnifications etc.

Both telescopes served up some excellent images, but this time there was a clear winner – the 130P.

Though the image flitted somewhat between perfect focus and slightly out of focus in both telescopes, both instruments revealed excellent details in the equatorial and temperate belts. Details in the more prominent NEB were more finely resolved in the Newtonian than in the ED90. But what clinched it for me was the sighting of the Great Red Spot (GRS) near the western limb of the planet (at 00:01UT) that was picked off in the 130P but was not seen clearly in the ED90.

As always, I would be very grateful if someone could repeat these observations if you have the 130P and a good 90mm refractor.

The 130P is turning out to be a fabulous little telescope and I am overjoyed to have made its acquaintance!

19:30 UT

I have noticed that the price of the ED90 has been bumped up by £48 in the short time since I acquired it for review. It now retails for £868?! I don’t know why this was done (it was £820 just last week, remember?), but I can tell you I do not consider these telescopes good value for money and do not understand some people’s obsession with them. Under good conditions the Heritage 130P will outperform it and for 1/6th of the price. And if the classical achromat is the prince of telescopes, Newtonians are the ruling monarchs.

I would like to keep this telescope and learn how best to maximise its potential. I have bestowed a name on her; Plotina.

After another beautiful, crisp day, the firmament was glorious after sunset, with a gorgeous crescent Moon adorning the western sky. I set up Plotina at the side of the house and trained her on our life-sustaining satellite. She cools super quick, faster perhaps than the ED refractor that now sits in its case. The view of Luna at 20x was simply breathtaking, with razor sharp crater fields and the most wonderful earthshine from its dark side. Cranking up the power to 165x, the image remained razor sharp with excellent contrast and without a trace of chromatic aberration.
After that, I headed over to eta Orionis, a fairly tricky double star and was rewarded by a good clean split of the A and B components, the primary shining about a magnitude brighter than the secondary (3.8 and 4.8, respectively) and separated by a mere 1.7 arc seconds. Because of its f/5 relative aperture, it is very important to examine such high resolution targets at the centre of the field. This can be achieved by placing the system at the eastern edge of the field and letting it drift into the centre. The procedure is repeated several times until one is certain that the duplicity has been unveiled.

Some haar moved in a short time ago but hopefully it will clear later. I hope to field my most powerful telescope, Octavius, to continue my study of the Giant Planet.

Saturday, February 13 2016


My luck ran night overnight, as instead of clear skies, we got a fall of snow.

The final step in keeping anything in my family is to get my wife’s approval. For that, I had to get all my facts together to make a convincing case lol:

The optical tube assembly weighs just 3.2 kilos

The little lazy Susan weighs 2.8 kilos

The telescope can be collapsed to half its length.

The tube assembly can be used with a variety of other mounts.

The telescope is easy to tweak; involving a couple of minutes with a laser collimator.

The telescope is easy to carry about using one hand, so even when I’m feeling lazy it will not overtax me.

The telescope cools rapidly, so no waiting around or extensive pre-planning involved. Just set it out 15 or 20 minutes before use and you’re cooking with gas.

Because the tube is open, the optics can be accessed to remove dust and other grime easily.

The telescope gathers a very decent amount of light to go that little deeper than my short-tube refractor; very good for deep sky viewing.

The telescope takes high magnification well; images remain sharp and well defined up 244x (higher powers not yet tested) when conditions are average to good, so will perform well on lunar, planetary and double star targets.

The telescope can be improved in a number of ways; for example, the mirrors could be re-coated to give both higher reflectivity and increased durability, the secondary size re-assessed, ways could be found to refine the helical focuser, a permanent light shroud can be installed  etc. Any amount of tomfoolery is permissible!

The instrument exudes charm and is popular with the kids.

The entire package cost only £129.

I think these points will be enough to win her over. Fingers crossed eh!

16:00 UT

Improving the Focuser:

As mentioned earlier, the focuser on the Heritage 130P is of the simple, helical variety. One simply twists it one way or another to attain a good focus. But in the field at night, it can be a little frustrating to focus precisely, especially when using high magnifications. Manhandling the focuser almost always causes the telescope to move a little, necessitating re-centering of the object under study.

Fortunately, I was able to find a very simple solution; about six inches of string!

A new improved focuser!

A new improved focuser!


The string is tied in a single knot around the focuser, gripping the top thread, and leaving two overhanging ends which can be pulled in either direction causing the focuser to move inward or outward, as desired. This enables both course and fine focusing with much less vibration or annoying image shift. I tested it out during the day on a variety of targets at various distances from about 40 yards to infinity and it worked really well! This will allow more quality time observing and more precise focusing from moment to moment.

I’m well happy with the improvement!

Sunday, February 14 2016


St. Valentine’s Day and the first Sunday of Lent.

Last night I fielded Plotina just before midnight. After snowing for much of the day, the late evening sky cleared up to reveal the hosts of the second heaven. Seeing was very good but bitterly cold(-4C), but I was rewarded by quite an extraordinary view of Jupiter and its magnificent satellite system. I watched the planet for about 40 minutes, beginning at 23:50UT and ending at about 00:35UT.

This instrument continues to humble me in many ways. The optics are unreasonably excellent in this telescope; something I was not really prepared for, but hand on heart, it has thus far given me the finest views of Jupiter in any small telescope that has passed through these parts. I made a quick sketch depicting the planet’s appearance at 23:50UT (CM II 217 degrees), when it was 33 degrees above the horizon. The Great Red Spot (GRS) was plainly seen in the eastern hemisphere of the planet. The magnification employed was 165x and a Baader Neodymium filter threaded to the 4mm Plossl.

Jupiter as it appeared though the Heritage 130P shortly before midnight on February 13, 2016. North is at the bottom and west is to the left.

Jupiter as it appeared though the Heritage 130P shortly before midnight on February 13, 2016. North is at the bottom and west is to the left.










Indeed, I was able to use this telescope to establish the most accurate longitude of the GRS during this apparition. The GRS was observed transiting the centre of the planet at 00:32 UT where the system II longitude was 243 degrees. Not bad eh?

In the immortal words of Alexander Pope;

Nature and nature’s laws lay hid in night;
God said “Let Newton be” and all was light.

Monday, February 15 2016


I subjected the 130P to a high magnification test on the first quarter Moon, at an ambient temperature of -1C. I am very happy to confirm that it handled 244x without flinching, with the craters, mountain ranges, maria and valleys  remaining tack sharp and colour free throughout. This is about as high as one would like to go with this telescope in the vast majority of applications and a testament to the quality of the underlying optics.

I would warmly encourage other individuals to test each and every one of the claims I have made about this telescope. Test everything; hold fast to that which is good.

Sound Biblical advice that!

23:15 UT

Way hay! I found me an online thread about the same telescope;  Enter the One Sky Newtonian from Astronomy Without Borders .

250K+ hits ……..Crikey!

Seems like I don’t need to say anymore, eh.

Watcha think?

Tuesday, February 16 2016


What a thread! The things they say about this telescope warms my heart.

That thread has saved me months of blogging; Laudate Dominum!

Gary Seronik of S&T also found the telescope a joy to use; see here.

And yet another independent review can be read here.

Here my story ends.

Thank you for viewing.

Post Scriptum: 

Thursday, February 18, 2016


Having just acquired the latest issue(March 2016) of Astronomy Now (pp 63), I read with interest that the current longitude (system II) of the GRS is 238 degrees. That’s just 5 degrees shy of my best estimate made with the 130P shortly after midnight on Sunday February 14 (see above). I’m thrilled to bits to have gotten so close with this nifty little travel Newtonian.

Monday March 14, 2016

I have found that the Televue bandmate planetary filter is a great match for the 130P whilst studying Jupiter.This filter will be used in all future observations of the planet with this telescope.

The Televue Bandmate Planetary Filter.

The Televue Bandmate Planetary Filter.

The primary and secondary mirrors of the Heritage 130P have been despatched to Orion Optics UK. Both mirrors will be re-coated with Hilux enhanced aluminium reflectivity coatings and a slightly smaller secondary (35mm @27% linear obstruction) is to replace the original flat.

Will report back on progress.

Tuesday, March 22 2016

The mirrors arrived back from Orion Optics UK this afternoon and I immediately set to work putting it all back together again.

Out came the matt black paint to darken the periphery of the new secondary mirror to further reduce stray light and increase contrast.

The primary mirror has been rocaoted with 97 per cent reflectivity Hilux coating. The smaller secondary ( also Hilux coated) is seen in the middle beside the original secondary.

The primary mirror has been re-coated with 97 per cent reflectivity Hilux. The smaller secondary ( also Hilux coated) is seen in the middle beside the original secondary.








Applying a coat of matt black paint tot he periphery of the new mirrors cuts down on unnecessary stray light entering the optical train.

Applying a coat of matt black paint to the periphery of the new secondary mirror cuts down on unnecessary stray light entering the optical train.











Side view of the recoated 130mm primary mirror.

Side view of the recoated 130mm primary mirror.














The primary mirror had to be re-spotted at its centre but this can easily be done by placing the mirror shiny side down on a sheet of paper and tracing round its circumference. Next, the 130mm diameter circle was carefully cut out and folded first in half, and then once again into quarters. When the paper is unfolded the centre is marked by the intersection of the two crease lines. A scalpel (lol!)was used to excise a very small hole at the centre of the unfolded paper and then it was placed over the mirror, being secured in position with some cellotape. Finally, a doughnut shaped sticker was placed on the spot exposed by the hole. Job done!

Marking the centre of the mirror for collimation purposes.

Marking the centre of the mirror for collimation purposes.









The optics were then rehoused in the tube, collimated using an inexpensive laser collimator (SkyWatcher) and briefly tested with an eyepiece. Everything looked dandy!The telescope should now deliver brighter, more contrasty images on all celestial targets. And those special coatings will last at least a quarter of a century!

Surely now Plotina will be as durable as any high quality refractor nay?

All I have to do is wait for a decent clear spell to see how well she performs under the starry heaven.

Plotina pining for a clear sky.

Plotina pining for a clear sky.










Wednesday, March 23, 2016

Jupiter as it appeared in the modified Heritage 130P travel Newtonian on the evening of March 23, 2016.

Jupiter as it appeared in the modified Heritage 130P travel Newtonian on the evening of March 23, 2016.

Beginning about 20:30 UT this evening, I took advantage of a clear spell after a few hours of light rain. Jupiter was about 34 degrees above the horizon and rising, and I continued observations through to 21:15 UT before more cloud rolled in. I captured some beautiful detail on the Jovian disk, including the appearance of the GRS at the planet’s eastern limb. As the minutes passed, the view of Jupiter got ever better as it gained in altitude. The 130mm f/5 performed flawlessly. The planet was brighter, crisper and cleaner than I had ever seen it before with this instrument under these conditions (Ant II). To say that I’m pleased with the modifications would be an understatement, but we’ll leave it at that.

I heartily recommend this telescope to my amateur friends across the world.

Wishing you all a very blessed Easter.

March 31, 2016

23:50 UT

I enjoyed a half hour with the Heritage 130P this evening after I had observed Jupiter. After spending some time in Leo hunting down some spring galaxies, I started looking at some double stars. Gamma Leonis was easy, Castor A and B just as easy, iota Cassiopeiae triple lovely and all three components resolved. Mizar & Alcor were glorious at 150x as was Polaris A & B. Izar (epsilon Bootis), a summer favourite, was high enough in the east for me to split it. These were all seen at 183x save for Mizar & Alcor. I then decided to try a pair of stars I haven’t visited in a while; Alula Borealis and Alula Australis in Ursa Major. They are high overhead this time of year. Aiming is quite difficult using just the RDF but with my 32 mm Plossl delivering 20x, I was able to frame them both in the same field. Starting with the orange star Alula Borealis, I employed 183x using my most comfortable ocular; the Mark III Baader Hyperion zoom set to 8mm with its 2.25x Barlow. Although this does not show the highest contrast views (but only by a surprisingly small margin!!), I was able to see the very faint spark of its companion. The primary is magnitude 3.5 but the secondary shines at magnitude +10.1 and only 7.4″ separating them! I was chuffed to see this in such a humble little reflector. Then came the icing on the cake; I moved south to Alula Australis (Xi UMa) and could see that the star looked ‘entangled’ but I knew I needed a little more power to get a clearer view. So I ran in and fetched by 6mm orthoscopic and coupled it to the little 2.25x Barlow yielding 244x, centred and focused carefully: Voila! The pair (1.6″ split) were beautifully resolved (magnitudes 4.3 and 4.8), the components round as buttons, with a kind of diffraction halo encircling them; kind of like an ‘aura’ encasing two luminous eggs in a wafer thin handkerchief lol.

I was absolutely beside myself in admiration for what this little telescope can do! I believe Newtonians have been terribly maligned as unsuitable for high resolution work relating to double stars but I now know that this is another myth. The telescope takes very high power well under reasonable seeing conditions and totally exceeded my expectations.  I feel privileged to finally ‘know’ and  to share this personal discovery with my peers.

If no one bothers, how can one ever discover the truth? The Heritage 130P is unreasonably excellent on everything; a great little bundle of joy!

April 7, 2016

Mr. Adam Blake from Pennsylvannia USA, was kind enough to share some video footage of Jupiter he captured with his One Sky Newtonian, as seen on the evening of April 5, 2016 during a spell of good seeing. He used an inexpensive 5X GSO Barlow and standard UV/IR filter on the camera at prime focus to capture the images, which have only been very lightly processed to show the telescope’s potential. See below.

Mighty Jupiter as captured by Adam Blake using the 130mm f/5 Newtonian on the evening of April 5, 2016.

Mighty Jupiter as captured by Adam Blake using the 130mm f/5 Newtonian on the evening of April 5, 2016.












I aimed the Heritage 130P at iota Leonis, now high in the south. Using 244x I was able to quite easily resolve A-B. The primary shines with magnitude +4.06 and the secondary +6.71 with 2.1″ separating the components. I would warmly encourage others to try this system, as well as the aforementioned star systems with this telescope.

A Portable Dew Buster: Are you concerned about dew building up on the open tube of the Heritage 130P? Nae worries! I never let any heating devices within a country mile of my telescopes, just like my forebears. I bought a portable three-speed fan for about £10 that zaps dew in seconds from the secondary and primary using cold air. Now you can enjoy the telescope under the stars for as long as you like!

Laudate Dominum!










April 28, 2016


At an ambient temperature of -1C, the Skywatcher Heritage 130P worked flawlessly to bag epsilon 1 and 2 Lyrae, eta Bootis (with its 10th magnitude companion), pi Bootis ( AB:  4.9, 5.8  separation  5.4″ and  AC: 4.9,10.6, separation 127″), alpha Herculis ( AB:3.5, 5.4, separation 4.6″ and a corker, AD: 3.5, 11.1, separation 79″)

For lunar and planetary studies, I can also recommend the Baader single polarising filter to use with this adorable little telescope. Retailing for £32.00, it significantly enhances belt detail on Jupiter, reduces glare and presents the planet in its natural colours.

The superlative Baader single polarising filter.

The superlative Baader single polarising filter.











Sunday, May 15, 2016.

The view from the sandy beach at Luss, on the western shore of Loch Lomond. May 14, 2016.

The view from the sandy beach at Luss, on the western shore of Loch Lomond. May 14, 2016.











During a relaxing weekend away with a group of old friends in the picturesque and historic village of Luss, on the western bank of Loch Lomond, I took the little SkyWatcher Heritage 130P along with me, as it was so easy to transport and set up. After long sunny days outdoors, I set the instrument (on its Dob mount) up on the garden table for a look at Jupiter and the first quarter Moon, which were perfectly positioned in the evening sky.

The Skywatcher Heritage 130P on holiday.

The Skywatcher Heritage 130P on short vacation.











As this was an annual event away, the crew were expecting me to bring along a telescope, but it is usually of the short refractor variety. I got some odd looks from the gang as I extended the upper stage of the ‘strange’ reflecting telescope, but I was sure glad I made the effort; they were all mightily impressed by the images the little portable reflector served up:- and even more gobsmacked when I told them how relatively inexpensive an instrument of this quality cost to acquire!

That's it guys: form a nice orderly queue.

That’s it folks: form a nice orderly queue.










A close encounter with the first quarter Moon: Kenny's face says it all!

A close encounter with the first quarter Moon: Kenny’s face says it all!












July 21, 2016

 LightBridge Mini 130 5.1" tabletop altazimuth mini-Dob reflector by Meade Print Home Telescopes The Meade LightBridge. Image Credit: Meade Instruments.

The Meade LightBridge Mini 130 5.1″ tabletop alt-azimuth mini-Dob reflector
 Image Credit: Meade Instruments.

My collegaue at Astronomy Now, Steve Ringwood, has independently reviewed the New Meade Light Bridge 130 Mini Dob for the August 2016 issue of Astronomy Now (now in the shops) on page 108-10. Although a slightly different design to the Heritage 130P featured in this blog, the optics are essentially the same but features a solid tube and a more traditional four spider-vane secondary support for even more rigid collimation maintenance in the field. Steve found that the optics were very good indeed, being capable of powers in excess of 200x, in agreement with my findings. At $200, it is priced at the same as the One Sky Newtonian from Astronomy Without Borders, discussed above.

So more choice for the discerning amateur.

Brian Schultz, from his YouTube channel Cool Space, describes how the One Sky Newtonian can be fitted to an inexpensive go-to mount for added versatility. See here for a video clip.

August 8-9 2016

The Old Man of Storr, Isle of Skye, as seen in the opening scenes of the block buster movie, "Prometheus".

The Old Man of Storr (elevated in the distance), Isle of Skye, as seen in the opening scenes of the block buster movie, “Prometheus”.

Our family ventured to the remote Isle of Skye, a place of outstanding natural beauty, for our summer vacation. My trusty 130mm f/5 Heritage Newtonian travelled with us. Though the weather was mostly damp and windy, I did enjoy a bout of observing with the instrument during brief clear spells on the evenings of August 8 and 9. The sky is truly glorious at this location, presenting some of the darkest and most transparent skies in all of Europe. And the (not so) little 130mm did not disappoint, serving up jaw-dropping views of the northern Milky Way high overhead, once the crescent Moon fell out of the sky. Deep sky objects were a joy to behold, including M31,Caldwell 14, M57, M13 and M92. The North American Nebula in Cygnus was as plain as the nose on the your face, as were the eastern and western Veil nebulae nearby.

Plotina ready for action on the remote island of Skye.

Plotina ready for action on the remote island of Skye.

I can also report that high resolution targets – including a batch of close test double stars – presented very well indeed. Images of systems such as Izar, delta Cygni etc, were calm and well resolved at high powers (243x), showing that this island has good seeing conditions for such work. Scotland has many such places(as I continue to discover) if one is intrepid enough to find them out!

September 30, 2016

My experiments with the Skywwatcher  Heritage130P continue apace. A while back a kindly gentleman from the USA alerted me to a potential issue with the instrument; the loss of precise collimation as the instrument is pointed to different parts of the sky. In a series of experiments conducted over the last six weeks or so, I discovered that while tightening the shaft that holds the secondary mirror in place seems to solve this problem for lightweight eyepieces, it doesn’t always hold collimation for heavier oculars such as the rather bulky, Baader Hyperion zoom.

As a consequence, I have reassessed the suite of oculars I use with the instrument and have switched entirely to smaller, more lightweight units. Below is an image of my current experimental set up; a 32mm Plossl, delivering a power of 20x and a 2.5 degree true field. Using the tiny, screw-on 2.25x Baader Barlow, I can couple the 32mm ocular to give a power of 45x and a true field of ~1.1 degrees – just large enough to frame the entire Double Cluster in the field!

For higher power work, I use a Parks Gold 7.5mm delivering 87x, a 6mm Baader classic orthoscopic yielding 108x, and a 4mm Revelation Plossl (fully multicoated) giving 163x. Finally, using the 2.25x Barlow I can achieve 243x and even 366x when mated with the 6mm and 4mm oculars, respectively. I also have an old 1.6x screw-on Barlow made by UK Astro Engineering, which gives me still more options to play with.The Barlows will increase the eye relief of the short focal length of the short focal length eyepieces too.

Plotina with a suite of lightweight oculars and low profile Barlows.

Plotina with a suite of lightweight oculars and low profile Barlows.

















Over the winter I hope to fine tune this set up some more, but I am very happy with the range of powers available to me and the relatively low cost of its operation.

I also intend purchasing some Bob’s Knobs collimating screws to fit to the secondary assembly in order to make collimation even more easy to achieve.

I will report back later in the year to tell you how I got on!

The instrument continues to inspire in so many ways and needless to say I have grown very fond of using it.

Thursday, October 13, 2016

Plotina received her new set of Bob’s Knobs secondary screws to make fine adjustments to collimation easier. I consider these to be a quality acquisition going forward.

Bob's knobs for easier adjustment of the secondary mirror.

Bob’s knobs for easier adjustment of the secondary mirror.

















Monday, October 17, 2016

Upon further investigation, I have been able to tighten up the stalk holding the secondary mirror in place by inserting a small washer, as shown below.

A simple washer tightens up the secondary support.

A simple washer tightens up the secondary support.

















This increased rigidity allows the instrument to maintain precise collimation even after moving the telescope wildly in altitude and azimuth. This was verified using a laser collimator. The telescope can now use larger oculars once again, including the Baader zoom.

Monday & Tuesday, October 18 and 19, 2016

A break in the wet autumnal weather over the last two nights has allowed me to conduct further tests with the SkyWatcher 130mm f/5 Newtonian. I fielded a 90mm apochromat (retained for further testing) side by side with the instrument and studied how both performed on a variety of high resolution targets located in different parts of the sky.

Test instruments: a 130mm f/5 Newtonian (left) and a 90mm apochromatic refractor (right).

Test instruments: a 130mm f/5 Newtonian (left) and a 90mm apochromatic refractor (right).

Yesterday evening, shortly before midnight, I compared and contrasted both instruments in respect of their ability to maintain crisp, bright images of a waning gibbous Moon. Once our satellite achieved a decent altitude, I cranked up the magnifications on both instruments and examined the cratered terrain along the day-night terminator. Both instruments performed well but the larger aperture of the Newtonian allowed me to employ significantly higher magnifications (in excess of 300x) before the image became unsatisfactorily dim for my liking. The 90mm refractor, in contrast, maxed out about 200x.

Tonight, with better seeing but in colder(+4C) and hazier conditions, I ran the two telescopes to a variety of double star targets at various altitudes; gamma Delphini, theta Aurigae, Iota Cassiopeiae and delta Cygni; these systems were deliberately chosen so as to test how the 130mm Newtonian would hold collimation as it was adjusted in altitude and azimuth. My results show that the insertion of the washer in the stalk supporting the secondary mirror (described above) worked perfectly well, the stellar images remaining crisp, round and tiny. In every case, the Newtonian produced brighter, more convincing splits of these systems under equivalent magnification regimes – 200 to 250x.

These results show that the Newtonian is a wonderful, cost-effective and versatile instrument for all celestial targets and is noticeably superior to a much more expensive 90mm refractor, which quickly runs out of both light and resolving power in comparison.

I continue to highly recommend this instrument to those who are looking for excellent performance on a limited budget.

Nothing more to say really.

Thanks for following this blog.

Best wishes,


Update: February 15 2017

My colleague at Astronomy Now, Ade Ashford, is helping to change culture by writing an excellent four page article on how to tune up the SkyWatcher Explorer 130PDS, mentioned in the blog above, and essentially the same telescope optically as the Heritage 130P (but with a closed tube) for better visual and photographic use. You can read this VERY interesting article in the March 2017 issue (page 98 through 102), out now.

Update: July 17 2017

Time: 00:09 BST

Location: Wigtown, Southwest Scotland.

Seeing: ( I to II): generally excellent, very calm

Instrument: 130mm f/5 Newtonian

Comments: A fabulous bout of double star observing. See notes below.











Update: July 18 2017

Time: 00:45 BST

Comments: Just in from another excellent session with the 130mm Newtonian. Highlight of the night was tracking down and resolving the lovely Mu Cygni. Tight pair, even at 244x and a fainter ‘companion’ wide away making it seem more like a triple system. Generous aperture and solidly good optics made very light work of this system. Like I said, this is arguably the best grab ‘n’ go ‘scope on the market today.  Details below;



Update: July 21 2017

Time: 00:35 BST

Instrument: 130mm f/5 Newtonian, aka ‘Plotina’

Seeing: Excellent (I); very clear before midnight. Some cloud moved in after midnight.

Comments: Still in Wigtown. Third night where conditions have been excellent.

Some very tricky systems resolved once again this evening with this modest telescope. Textbook perfect results!











Update: April 4 2018

The Astronomers Without Borders, One Sky Newtonian thread has now exceeded 300,000 hits!



De Fideli.


Beauty and the beast: my 130mm f/5 Newtonian versus a 90mm f/5.5 ED refractor

















Date: Wednesday March 28 2018

Time: 22:00UT

Temperature: −2C

Seeing: III, bright gibbous Moon, small amounts of cloud cover in an otherwise clear sky.

It is often claimed that refractors give more aesthetically pleasing images of celestial objects than reflectors. But how true is this statement? Last night, I learned yet another instructive lesson that shatters this myth once and for all.

Earlier in the evening, I fielded my 8″ f/6 Newtonian against a very good 90mm f/5.5 ED apochromat. The target was Theta Aurigae, then sinking into the western sky and so past its best position for observing. Seeing was only average. Both telescopes had been fielded about 90 minutes earlier with the optics capped, so both were completely acclimated. I charged the apochromat with a 2.4mm Vixen HR eyepiece yielding 208x. The 8 inch Newtonian was charged with a 6mm Baader orthoscopic ocular delivering 200x.

Examining the system in the 8 inch reflector showed the primary star as a slightly swollen Airy disk but the faint companion was clearly visible. In contrast, the view through the 90mm refractor showed a less disturbed primary but the secondary(for the most part) couldn’t be seen!

Question: How can an image be deemed more aesthetically pleasing when a prime target (the secondary) in that said image can plainly be seen in one instrument and not in the other?

Date: Thursday March 29 2018

Time: 00:05 UT


Seeing; II/III, slight improvement from earlier, otherwise very similar.

Later the same night, I fielded my 130mm F/5 Newtonian along side the 90mm refractor and  turned my attention to a spring favourite; Epsilon Bootis, now rising higher in the eastern sky.

This time, I charged the refractor with a 2.0mm Vixen HR eyepiece yielding 250x. The Newtonian was fitted with a Parks Gold 7.5mm eyepiece coupled to a Meade 3x Barlow lens giving a power of 260x.  Examining the system, I was quite shocked by the difference between the images; the refractor did show a dull, greenish companion but it was entangled in the diffraction gunk from the orange primary. What’s more, the entire system was surrounded by chromatic fog owing to the imperfect colour correction of the refractor (an FPL 51 doublet). In contrast, the 130mm f/5 Newtonian image was far superior in every way; the Airy disks were smaller, tighter and more cleanly separated, and with zero chromatic fog to be seen. The Newtonian image remained just as stable as in the refractor image throughout the observation! The components also displayed their pure colours (as only a reflector can yield); the primary orange and the secondary, blue. In a phrase, the differences between the images was like night and day!

Conclusions: The 130mm Newtonian provided a much more aesthetically pleasing image than the refractor, which was compromised by its smaller aperture and less than perfect colour correction. As a small portable telescope, the Newtonian is far more powerful and is capable of delivering images that are simply in a different league to the refractor.

ED 90 Refractor: Proxime accessit.

130mm f/5 Newtonian(Plotina): Victrix/Pulcherrima!


Postscriptum: As always, I would encourage others to test these claims. Truth matters.



Neil English is author of Grab ‘n’ Go Astronomy.


De Fideli.



My Wonderful Fastnewt 130 F5!

The extraordinary 130mm F/5 super travel ‘scope.

















A little over two years ago, I first began exploring the potential of a 130mm f/5 Newtonian reflector. As you may recall, I was really quite impressed with what the telescope delivered for its very modest price tag, something I had come to expect after the very positive experiences I had had with a larger 204mm f/6 Newtonian for a whole year. Both telescopes were made by SkyWatcher, and had excellently figured parabolic mirrors with smooth, colour free optics. These collective experiences transformed my opinion of Newtonian reflectors, so much so that I have come to prefer them to my erstwhile favourite type of telescope; refractors.

The 130mm f/5 Newtonian is a very convenient telescope for travel and quick grab ‘n’ go excursions. Indeed, in one form or another, this telescope has travelled the length and breadth of the country with me and has never failed to deliver excellent views on all classes of celestial real estate. Over the 25 months I have owned it, it has clocked up well over 100 hours under the stars. Indeed, it was so easy and comfortable to use that I invested in making an already good ‘scope into a great one. I upgraded the flat to one of higher quality and had both mirrors treated with the best coatings money could buy. In previous blogs, I have described how I re−housed the open tube configuration into a more stable closed tube configuration with a better focuser. I also described how I lined the inside of the tube with cork before covering it with standard flocking material. All of the modifications were very cost−effective and, all in, set me back just a few hundred pounds.

I have enjoyed extraordinary success with the 130mm f/5 in my pursuit of double stars. It has resolved double stars down to 1.0” and elongated 0.9” pairs. And in recent months, I have been able to add a few more strings to my bow, including Iota Leonis and Eta Geminorum to name but two; systems that I found to be very difficult with top quality refractors of 4− and 5−inch pedigree under good, stable skies. Indeed, my notes confirm that on these and other high−resolution targets, the 130mm f/5 was more proficient than a 4−inch f/15 classical achromat, in violation of a tradition that hearkens back to the 19th century, and shattering forever the myth that good Newtonian reflectors cannot serve as first rate double star telescopes.

I can reaffirm the beneficial effects of insulating the tube of my 130mm reflector. My ongoing studies have shown that it significantly reduces tube currents while the ‘scope is acclimating, and in use, I have seen with my own eyes the beautiful, ultra−high magnification views of various tricky double and multiple stars. I would estimate that the insulating material consistently provides text book perfect images at the highest powers I have used with this telescope (over 400x on some objects during spells of good seeing) about 30 per cent more frequently. In addition, and as previously noted, the instrument is also an excellent lunar and planetary telescope for its size, as well as being a very satisfying deep sky instrument.

My success with double stars is particularly noteworthy, and I wanted to communicate another surprising advantage of using a small aperture Newtonian reflector like this. Anyone reasonably well acquainted with optics will tell you that as the f ratio of the primary mirror decreases, so too will the size of the field that is free of coma (an aberration that is particularly important to consider in high resolution double star work). So, conventional wisdom would say that an f/6 ‘scope will have a larger coma free field than an f/5 instrument and so on. But is this true? Surprisingly, the answer is “not exactly.” Let’s do the math to see what I mean.

The coma free field of a Newtonian system in millimetres, scales directly as the cube of focal ratio. Specifically;

The coma free field = 0.022 x f^3.

So, for my f/5 Newtonian we obtain a coma free field = 0.022 x 5^3 = 2.75mm.

Next, consider how this translates into true field.

True field in radians is given by; coma free field/ focal length.

Thus, expressed in radians, the true coma free field in the 650mm Newtonian will be:

(2.75/650) = 0.0042, and converting to angular degrees gives 0.0042 x 360/2pi = 0.24 degrees.

Consider next a typical high−power eyepiece used in double star divination. A popular choice I like to use is a Parks Gold series 7.5mm, coupled to a 3x Barlow lens, with an AFOV of about 50 degrees. This yields a power of 260 diameters in the 130mm f/5, so the coma free field at this enlargement is: 260 x 0.24 = 62.6 degrees!

This means that there is no coma to worry about across the entire field of view using this particular configuration. In contrast, if I were to use a 2.5mm Nagler or some such, offering an AFOV of 82 degrees, the periphery of the field would have some coma.  This observation helps explain why I have done so well using comparatively simple eyepieces!

Favourite double star tools: a Meade 3x Barlow (laevo) and a 7.5mm parks Gold ocular (right).

Curiously, we can do the same calculation for my 8” f/6 Newtonian, which has a focal length of about 1200mm, yielding 0.23 degrees; slightly smaller than offered by the 130mm f/5!

Another consequence of this result is that the coma free field will be proportionally smaller in larger instruments of the same f ratio. Consider my 12” f/5 Newtonian, for example. In comparative terms, a power of 260x will only deliver a coma free field of 26 degrees, which is only about 27 percent of the true field delivered by an ordinary 50 degree AFOV eyepiece.

This agrees with experience; to get the best images at 260x from my 12” f/5 , I have to keep the objects in the centre of the field to derive the best images.

                                                        On the Road

In need of a sturdy case.
















I’m a sentimental observer, and I have grown to love my 130mm f/5. I hope to travel further afield with it this coming summer, God willing, when our family will visit the south of Ireland. Here, I’ll hopefully be able to view Jupiter fully 5 degrees higher in the sky than I can at my adopted home here in Scotland. This will be about 8 weeks after it reaches opposition in May, but with the return of truly dark skies for a few hours at this more southerly latitude, I’m hoping that it will make a significant difference to the views. Fingers crossed eh!

For travel, as well as for just general storage of the instrument, I decided it was high time that I invested in a sturdy case for my “Fastnewt 130 F5.” I pulled the trigger earlier today by purchasing a decently priced aluminium flight case, with dimensions of 850 x 295 x 270mm. Here’s the link. I’m hoping this will give me enough room to store the telescope, finderscope, various eyepieces and Barlows, guide and note books etc for hassle free conveyance to our various destinations. As soon as it arrives, I’ll chime in again with news on how I get on with it.

March 9 2018

A fine looking case for my Fastnewt 130 F5.















A great case for a great telescope.


Well, the package containing my carry case finally arrived today after a delay of a few days owing to the dreadful weather of late. I’m delighted with it. It’s light weight and sturdy, and should fit the instrument as well as other stuff as I had planned. All I need to do now is cut the foam to size and I’m in business!

After supper I set to cut the foam. Here is the final result. I think it looks dapper!

Snug as a bug in a rug, ken.

















My new case has brought instant domestic dividends! You what mate? It’s got my wife off my case lol. You see, she’s always nagging me about how the Fastnewt 130 F5 clutters up our hallway. It was more or less permanently mounted on my Vixen Porta II from the day I acquired it. Now it has its very own space; a place prepared for it.

I was a bit over ambitious about just how much I expected to pack into the case. My guide and note books didn’t make the cut (excuse the pun lol); they’ll go with the general luggage; no sweat. There’s a silvery (foam) lining though; my home made flexi dew shield just sits ’round the optical tube, and the deep incisions I made to accommodate the finder ‘scope can also carry filters; a variety of kinds; polariser, colour and planetary. Because Jupiter will be low in the sky, colour filters, in particular, will help clean up the images. The polariser will serve me by day, cutting through glare.

March 10 2018

I am lucky enough to have acquired some very nice oculars over the years and have come to appreciate many of them. The f/5 optical system serves up very good images with fairly simple eyepieces, such as orthoscopics, Plossls and even Kellners (on axis). Some of my favourite eyepieces include my 32mm SkyWatcher Plossl, which is my main wide field eyepiece with the Fastnewt F 5, delivering a well corrected 2.5 degree true field; plenty big enough for the vast majority of deep sky objects. For medium power work, I enjoy the widefield options delivered by my Mark III Baader zoom (particularly at the 8 and 10mm settings), but also appreciate the more contrasty views served up by 6mm Baader orthoscopic as well as a 7.5mm Parks Gold eyepiece and a 10mm Orion Explorer II Kellner. For high power work, I am fully sated by amplifying these eyepieces using either a 2.25x or 3x Barlow.

The extra aperture afforded by the 130mm parabolic primary mirror takes grab ‘n’ go to a whole new level of experience; and that’s not a hyperbola! Five years ago, I may have been cajoled by articles like this, but having owned and used many small aperture refractors (including a Zenithstar 66 SD doublet & triplet, SkyWatcher ED 80, Takahashi FS 60C, TeleVue 76, Tele Vue Genesis (original f/5 fluorite model), Tele Vue 102, Skywatcher ED100, and even long (but still small apertured) Skylight 4″ f/15 and Moonraker 80mm f/15 achromats), to name a sizeable fraction, they were all vanities of sorts.

Newtonians alerted me to this rose−tinted, but ultimately delusional state. I just sensed something was wrong.  In contrast, I discovered an honesty in the Newtonian reflector that simply wasn’t there in other telescopes. You do get what you pay for, that’s for sure.  But from a purely visual perspective, you get a whole lot more with the Newtonian! I was seeing more details, capturing more light and extending my target base with the 130mm reflector. Denying or dismissing these facts is a vanity!

Faster, cheaper, better!

As stated in previous blogs, the Fastnewt 130 F5 is truly fast in other regards; most especially cool down. Indeed, (and unlike the Fastmax 180 F4.5) its open tube configuration and small mirrors ensure rapid acclimation without the need for fans and other active cooling systems. The provision of Bob’s Knobs on both the primary and secondary mirrors means I can fine tune collimation in seconds when the most exacting optical ‘syncing’ is called for.

As you may know, I am especially passionate about observing double stars. And the 130 F/5 Newtonian has turned out to be a fine instrument for teasing out pairs down to the theoretical limit imposed by its aperture. I enjoy watching such pairs and triplets moving through the field at ultra high powers. Here are a few sketches of systems I’ve just recently visited.

Iota Leonis: a tricky system in the southeastern quarter of Leo.

















A couple of other delicate systems as observed with the telescope.


The first drawing shows Iota Leonis, resolved using a 6mm Baader orthoscopic coupled to a Meade 3x Barlow delivering 318 diameters. The second set of drawings are of Mu Bootis(Alkalurops), a most delicate triple system, and Delta Geminorum (Wasat). These were imaged using my 7.5mm Parks Gold and 10mm Kellner, respectively, coupled to the same 3x Barlow. Over the last couple of years, I’ve managed a whole suite of difficult pairs with this telescope and it continues to go from strength to strength.

March 12 2018

I gave up on equatorial mounts after I quit doing CCD imaging and film astrophotography. I felt liberated in being able to find things using muscle power, eye and brain. No wires, battery packs, heavy counterweights and finicky cameras to think about. There is great virtue in such simplicity; it brings peace and joy in equal measure.

The Fastnewt 130 F5 sits pretty astride the Vixen Porta II mount. I have owned this piece of kit for about six years now and it has carried all manner of small and medium sized telescopes. It is an excellent match for this instrument and is gifted with slow motion controls. Over the years I’ve trained myself to use these controls to follow targets, even at very high powers. For example, during a recent excursion, I was following a double star target at 406x fairly comfortably  While looking through the telescope, I grasp both controls and make very gentle adjustments so as to keep the object centred, even in a very narrow field!

Faithful companion; my Vixen Porta II mount.

















This kind of work is equally amenable to sitting or standing modes. And it’s made possible by virtue of the close proximity of the focuser to both the azimuth and altitude controls. Such a configuration confers maximum stability for exacting, high power work.

Mechanically it’s been sound; strong, light−weight and modular, breaking down into easily stored and transportable components. It works in all seasons, and here in Scotland you really can experience all four in one day! But like any ole jenny, the Porta can have its moments. The plastic knobs of the slow motion controls have a habit of coming loose…..sometimes during very critical observing moments. That’s why I always check ’em over before beginning a vigil. Having said that, I am now looking into ways of improving these also. That said, there is such a thing as overdoing it; check out what this bloke did with his Porta lol.

The clever design of the Porta enables it to used in spotting ‘scope mode during daylight. I am enjoying my 10mm erecting eyepiece, which delivers a correctly orientated view at 65x with a 2mm exit pupil, but I’m equally enthralled at seeing the details of nature at super high powers, thanks to its superior light gathering power and resolution over a conventional spotter. When you’re using 150x and upwards, it matters little whether an object is upside down or rightside up. This is possible because my climate here does not (as a general rule) endure large diurnal temperature variations and that leads to stable air masses, allowing me to capture wonderful details of nature over distances up to a few hundred yards.

March 14 2018

Pi Day!

Stephen Hawking has gone to meet his Maker. The poor man suffered for so long, trapped in the prison of his wheelchair. May the Lord have mercy on his soul.

Once upon a time, I entertained a dream to have my very own observatory, but now that I’ve matured as an observer, I have little desire to create one. I’ll always have a mancave of sorts though, but not an observatory. My modus operandi is open air observing, using telescopes I can manage; so that confines me to instruments of 12 inches or smaller. I own all the telescopes I could possibly wish for in life. As I get older, I will likely use smaller telescopes more frequently, and the ultraportable Fastnewt 130 F5 will thus remain an important instrument in my arsenal. Right now, I’m in the prime of my life and can enjoy my 8 and 12 inch telescopes just as much as the 130. As good as the latter telescope is, there are many things in the firmament that are beyond its reach. There is a time and a place for them all.

Acquiring a solid tube for the optics at the heart of the 130mm f/5 has proven to be a good move. I can remove the instrument from its case and mount it with little in the way of collimation adjustment. Certainly, it is a great step up from the original Skywatcher Heritage 130P (open tube) in this regard, but with very little additional mass.

Corbie watching.

















I am very much enjoying using the telescope as my new spotting ‘scope for nature studies. It’s a pure joy to watch the noisy corbies that make their nests in the conifer trees near my house. The telescope produces beautiful, sharp images and even on a dull day like today its generous light gathering power makes such observations very worthwhile. You don’t miss a trick with a telescope like this! Sometimes they look straight at you and you can see the light in their eyes. I sometimes wonder whether they see me better than I see them!

The telescope also allows me to monitor the buds on the trees as Spring progresses. Horsechestnuts are among the first to bring forth their leaves ’round these parts. I can tell you that they’re well on their way, but will need a few warm, sunny days before we will see their full glory, draped in harlequin green.

Nature waits for no man.

I understand that some folk are reluctant to use Newtonians in terrestrial mode because the tube is open to the elements. But this too is a vanity. As I’ve described in a previous blog, Newtonian optics are easy to clean, and any dust that falls inside the telescope can be easily removed. I find cleaning the optics once or twice a year is plenty often enough. It’s not afraid of pollen, or dust, moisture or even an adventurous spider! Whatever makes its home on the optics or in the tube can be removed; no sweat.

March 15 2018

Well, the weather has taken another down turn. Hoping for some more clear skies, but no go, unfortunately. I do however have a wee treat for you; I found this review of a close kin of my 130mm Newtonian; enter the Vixen R130SF. This lady provided a good review of this telescope on a Porta II mount no less. The reader will note that no mods of any kind were made in this report, but I think you’ll agree that she ticks many of the boxes I have covered in my own exploration of this telescope.

March 17 2018

Lá ‘le Pádraig sona daoibh!

The Fastnewt 130 F5 has been tested in all weathers. I’ve enjoyed it at temperatures as low as minus 10C and as high as +25C. In general, the telescope performs better in milder weather but I have encountered textbook perfect images on many freezing cold nights.

When the weather is settled, I usually bring the instrument out from a warm, indoor environment and let it cool off to ambient temperature. Low powers can be enjoyed pretty much immediately, whereas medium power views (up to 100x say) are fine to explore after about 10 minutes. But for the most critical observations at very high powers, I usually give it at least 30 minutes.

In unsettled spells, such as those we are experiencing just now, I leave the telescope in a dry, unheated outhouse, so that it can be deployed at a moment’s notice. This is a strategy that works well for all kinds of telescopes. That way, I can enjoy the telescopic heavens even during the briefest of clear spells.

Like any other activity, preparation will always be your friend.

Time: 22:10 UT

Observing during a cold snap.

















The great French scientist, Louis Pasteur, was fond of saying, “chance favours the prepared mind.” I think this is true. Though the heavens declare that Spring is here; the weather says otherwise. Indeed, this is the coldest St. Patrick’s Day I can remember in many years. A biting easterly wind brought in more snow and temperatures struggled to rise above zero today. But I did get a short half hour spell this evening with the telescope between snow showers, and to my sheer delight I discovered that conditions were excellent. Northerly winds almost invariably bring turbulent air in this location, and quite often, those from the east are little better. But there are always exceptions. Shortly after 9 pm local time, I was able to visit a few of my favourite double stars; Polaris A & B, Theta Aurigae and Iota Cassiopeiae; old friends from the depths of space. Indeed the images served up were so good when the wind died down, I was able to make a recording of what the 130mm f/5 showed me at 183x. A telescope of this size will show a very delicate 1st Fraunhofer diffraction ring ’round Polaris A, a magnitude 2.0 star, together with its tiny spark of a companion. A similar looking system; Theta Aurigae, is significantly fainter; just +2.6. In contrast to brighter Polaris though, the first diffraction ring is much more subdued. It follows that fainter systems will show even less of their diffractive effects; a good thing when it comes to observing these beautiful, delicate wonders of nature.

Below is a pair of drawings I made to show these differences.































By 9:45 pm, the situation had deteriorated. The clear sky was gone and another snow shower had begun.

Still, it was good to get out, if only for a wee while!

March 23 2018

Time: 18:30 UT

The snow has gone and it’s beginning to look more springlike.

After attending a couple of students, I set up the Fastnewt 130 F5 in my garden near the closing of the day, in anticipation of a wonderfully placed 7 day old Moon. The Moon is especially good to observe in March and April, when we obtain the most magnificent displays of earthshine. It also gains altitude during the earlier points in its cycle. And while it has crossed the meridian by now, it is very high up in the sky and that means the chances are high that I will obtain beautiful images over a range of magnifications.


















The forecast promises to maintain clear skies well into the night, so I’ll have more opportunities of using the telescope; and not just on the Moon. If conditions are good, I’ll be able to resume my favourite passtime of double star observing. Fingers crossed!


Well, it was a bit of a mixed bag this evening. Conditions were rock steady but the sky became progressively more hazy as the evening went on. That said, the views of the Moon did not disappoint, especially earlier in the evening, when the haze was less obtrusive. As I mentioned in this and ealrier blogs, the Fastnewt 130 F5 delivers excellent views of the Moon and planets, when suitably placed, courtesy of its very decent aperture compared with more ‘traditional’ grab ‘n’ telescopes.. I recall with great fondness the wonderful images the telescope served up on Jupiter during last year’s opposition and even though its positioning in the coming months (it transits low in the sky about 4am at the moment) will be far less favourable than in 2017, I’m still very excited about seeing the giant world again through this telescope.

Hazy conditions often bring excellent, steady images. That much was clear when I visited some of the brighter double stars this eveing; Castor, Theta Aurigae, Algieba, Cor Caroli, Alula Australis, Mizar & Alcor and a few others.Newtonians rock when it comes to double stars and there are very encouraging signs that more and more amateurs are using these telescopes in their pursuit.

By 10:00pm local time, the haze became so dense that only a few of the brighter luminaries dierctly overhead were still visible. But not a bad innings nonetheless!

March 24 2018

I hope to employ the Fastnewt 130 f 5 in all the ways I’ve described for the rest of the spring and will report back after our trip to the Emerald Isle later this summer.

Thanks for keeping up with this blog.

Until then; farewell and best wishes to you all.



To be continued………..


De Fideli.

Changing Culture V: Using Newtonians in a Terrestrial Setting.

See the difference.

















In a previous blog, I described, in considerable detail, my enthusiasm for the lightweight but powerful 130mm f/5 Newtonian reflector. This modest instrument beat the codpiece off a way overpriced 90mm ED apochromat which retailed for about £1,000 (and is now discontinued) on every test object. This little Newtonian has an excellent SkyWatcher parabolic mirror and the secondary was upgraded to an Orion Optics UK sourced unit, with a semimajor diameter of 35mm, thus delivering a moderate 27 per cent linear obstruction (so considerably smaller than a similarsized SCT or Maksutov). Both mirrors were also treated with Orion UK’s proprietary HiLux coatings, providing an overall reflectivity of 94 per cent. Further testing showed that it provided images that were effectively equal in brightness to a fine 127mm f/12 refractor (which has now been retired). The interior of the tube was lined with cork for improved insulation and then covered with standard flocking paper, maximising contrast and reducing stray light to near zero.

Such an instrument has provided excellent views of the heavens, from 20x in a 2.5 degree true field, to over 400x on very tricky double stars down to 1.0″ separation. During last year’s apparition of Jupiter, the 130mm f/5 Newtonian also proved its worth as a very capable planetary telescope. The instrument was also fitted with easytouse Bob’s Knobs on both the primary and secondary for ultraprecise collimation that takes just seconds to execute.

Newtonians need to be very well flocked to serve as effective terrestrial telescopes.

















It may come as a surprise to some readers to learn that this author spends as much time looking through telescopes by day as by night, and over the past few months, he has been using the 130 as a ‘super’ spotting ‘scope, where it has dlivered crisp, colourtrue images of a range of terrestrial targets, including, birds, trees and various manmade landmarks. This has led him to openly question the dominance of more conventional spotting ‘scopes (usually small refractors and catadioptrics). The only reservation I had while using the Newtonian for nature studies was that it delivered an image which was upside down and rightleft reversed. And while this ought not to bother a determined telescopist, some have dismissed the small Newtonian as a daytime spotting ‘scope precisely because of the orientation of its images. Yet, there are ways to produce correct orientation views through Newtonians and it doesn’t require expensive prism diagonals and the like; enter the Newtonian erecting eyepiece.

The SkyWatcher 10mm Newtonian erecting eyepiece.

















I was able to get hold of a 10mm focal length ocular marketed by SkyWatcher for less than £30. It has basic but effective antireflection coatings and appears to consist of a simple Kellner design with an extra lens inserted so as to invert the image at the focal plane and, unlike conventional refractor diagonals, it flips the image so that left and right are correctly presented.

The 10mm SkyWatcher erecting eyepiece has basic anti–reflection coatings.

















The eyepiece delivers a power of 65x, with a near 2mm exit pupil, which closely matches the diameter of my pupil during bright daylight. Optically, the unit delivers good, sharp images, with a welldefined field stop, although critical tests did reveal a small amount of lateral colour. Contrast is good but not quite in the same league as a dedicated astronomical eyepiece endowed with fully multicoated optics. Yet, it is more than adequate for casual nature studies.

The instrument can be focused on objects as near as 25 yards without adjusting the position of the ocular, but by moving the eyepiece further up the barrel, or using the supplied extension tube (pictured below),objects even closer to the telescope can be brought to a good focus.

The extender tube supplied with the 10mm SkyWatcher erecting eyepiece.

















Doing an internet search, I have also become aware of a 20mm model (supplied by Celestron with some of their smaller Newtonians), which would produce a power of 33x or so with the 130. This would be a useful addition for those wishing to extend the range of magnifications achievable with the telescope during daylight hours, and I will report back on this if I am lucky enough to find one.

Using the supplied extension tube allows the 130mm spotter to focus on objects as close as ten yards.

















So to summarise, there is absolutely no reason why observers possessing small Newtonian reflectors cannot use them in a variety of terrestrial applications. Their increased light grasp and resolution over conventional spotting ‘scopes and small refractors will both surprise and delight their users. The range of terrestrial eyepiece options available are quite limited at the moment (as far as I can tell) though, but I would warmly welcome the introduction of more models offering a greater range of magnifications, as well as improving the optical quality of these designs. But one thing is clear; using erecting eyepieces increases the verstaility of what is, already, a great, allround ‘scope.


Neil English is the author of Grab ‘n’ Go Astronomy.





De Fideli.

Some Experiments in Thermal Management with a Newtonian Reflector.

The author’s 130mm f/5 Newtonian reflector enjoying a winter wonderland.


















As explained in earlier blogs, I have discovered, through extensive experience in the field, that Newtonian reflectors can render beautiful, colour free images of a wide variety of celestial objects, from the Moon and bright planets, to a wealth of bodies beyond the solar system. In my own niche area of double star observing, I found that a simple 130mm f/5 Newtonian reflector resolved tighter pairs than a 90mm ED refractor and indeed, as deduced from my previous field notes, also exceeded the performance of a very fine 102mm f/15 classical achromat on good nights of seeing.

Refractors have a well earned reputation for garnering very stable images at the eyepiece, a consequence of the decent height of the entrance pupil above the ground, glass properties (crown & flint doublet objectives in particular), less intense tube currents and relatively small apertures which are quite often immune to the vagaries of the atmosphere. In comparison, reflectors can be rather temperamental. With their need for precise collimation and greater tendency to manifest thermal effects coupled to the (often) larger apertures employed in the field, Newtonians typically (but not always) serve up images significantly more unstable from moment to moment.

As I also explained before, this is not really a big issue for a seasoned observer, who has more than enough patience to remain observing long enough to ignore or wait for the disappearance  of these various bugs that attend the use of a good Newtonian telescope. That having been said, I elected to investigate the effects of some simple modifications that could potentially ameliorate the effects of tube currents in the 130mm f/5 Newtonian, so as to stabilise its images as much as possible.

This led me to investigate the effects of insulating the inside of the thin, rolled aluminium tube that houses the optics of this small Newtonian. My researches led me to explore the properties of cork; one of the best, natural and renewable insulators from the Creation.

I heard many a yarn recounted by veteran observers, that lining the inner tube with cork could dramatically dampen the effects of tube currents in Newtonian and compound telescopes. It seems to have originated sometime in the late 19th century or early 20th century, but in more recent years, some amateurs, whose work I trust, have also recommended cork as a suitable insulator for their telescope tubes.

The theory is fairly simple; the thin aluminium tube is an excellent conductor and radiator of heat. Indeed, under a clear sky, the temperature of a metal tube rarely tracks the ambient air temperature perfectly but instead can often fall off to a few degrees lower than the surrounding air during radiative cooling in the field. But by lining the inside of the tube with some kind of insulating material, one can keep this temperature differential between the aluminium tube and ambient air to a minimum.  This should create more stable images, especially at the highest powers, which would in turn make their visual study more profitable, as well as increasing their aesthetic appeal.

Materials & Methods

I checked out what types of cork were available and settled on the purchase of self adhesing cork sheet, which arrived promptly from the seller. Next, both the primary and secondary optics as well as the focuser were completely removed from the aluminium tube, which was then lined with the cork sheet.

Thin sheets of self adhesive cork can be purchased inexpensively from many retailers.

















Initially, I had just intended simply to paint the cork a flat black colour but was unconvinced that it was really dark enough to compare with regular flocking material. I therefore elected to cover the cork with the flocking material, which, in effect, would act like a double layer of insulation. After lining the tube with the cork overlaid with the flocking material, I also lined the drawtube of the focuser with more flocking material before putting the telescope back together again.  I was very pleased at the light dampening properties of the instrument  during daylight hours and noted that the images served up by the telescope were a little bit more contrasty than before the flocking material was added. The result is seen below:

The wonderfully dark interior of the telescope tube to improve image contrast.

















Finally, I was now ready to study the images of a variety of high resolution targets to see whether or not this tube insulation worked in practice. My tests were carried out over a number of winter evenings, where the ambient temperatures sometimes fell to −10C. Most of my observations were conducted on the evenings of January 18, 19, 20 and 24, but also included some shorter vigils during more unsettled spells. The telescope was given time to cool off to near ambient before commencement of observations.

The targets included some tricky double and multiple stars; theta Aurigae, delta Geminorum, iota Cassiopeiae, as well as  easier subjects like Castor A & B. In each case, I charged the telescope with a power of beween 260x and 406x diameters (so between 52 and 80x per inch of aperture) and the images studied as they moved across the field of view.


The carefully focused stellar images were very impressively presented in the telescope and appeared significantly calmer (read less susceptible to thermal degradation) as they moved across the field, their forms morphing significantly less than I had previously noted in the uninsulated tube. Indeed, during these vigils I enjoyed some of the finest images  yet garnered from this modest telescope. Specifically, the stellar Airy disks were much more in keeping with those I have enjoyed during the milder months of Spring and Summer. I was able to pick off faint and close companions much more easily and efficiently than I can remember when using the same optics in previous winters. The activity of insulating the inner metal tube most definitely improved the images from moment to moment, allowing me to enjoy their perfect forms for longer.

Further Comments

My correspondence with some highly experienced observers also alerted me to other ways tube currents could be minimised or even completely abated in Newtonians, including housing the optics in an oversized tube, constructing non cylindrical tubes (think hexagonal designs) and using active mirror cooling. A combination of all these strategies have been shown to improve image stability in reflectors and are well worth investigating in their own right. They will surely make an already good telescope into an excellent one.

I intend to insulate my larger Newtonians in the same way, and in due course.


The author would like to thank Martin Mobberley and Garyth64 for interesting discussions on cork.