Plotina: a 130mm f/5 Newtonian that just goes on debunking myths promulgated by armchair astronomers, poodle pushers and fake theorists.
August 15 2018
Preamble: No doubt you’ve heard one or more of these statements before;
” My skies are never good enough to get steady views”
” The bleedin’ jetstream always gets the better of me.”
“The British Isles suck when it comes to doing visual astronomy.”
” Climate change is making our skies more cloudy, making small refractors more profitable to use.”
” It’s been cloudy for weeks and months on end.”
” My refractor cuts through the seeing like nothing else!”
What do they all have in common?
Lies, more damn lies, or gross distortions of the truth!
You see, I’ve been doing my homework, testing out a modest 130mm f/5 Newtonian reflector all over the British Isles, and finding that many places are plenty good enough for doing high-resolution planetary, lunar and double star observing. And from dark places, low-power, deep sky observing is also very much worthwhile.
Don’t believe me?
Do I sound like I care?
Stick this in your proverbial pipe and smoke it: if only you got off your big, fat, wicked, lazy butt and did some real testing you’d soon come to a knowledge of the truth!
Moi? I’ve observed with the same telescope from no less than five counties in Southern Ireland, the windswept Isle of Skye in Northwest Scotland, Aviemore in the heart of the Scottish Highlands, and rural Aberdeenshire in Northeast Scotland, Wigtown in Southwest Scotland, Seahouses in Northeast England and even in the heart of the large cities of Glasgow and Edinburgh. Most recently, I tested a site in southern Lakeland, Cumbria, the subject of the present observing report.
Thus far this year, I have logged 78 separate sessions under the stars (not all perfectly clear and not all long sessions), either at home here in my rural site just north of the Scottish Central Belt, or while on holiday, and no doubt there were still more nights when I was unable to observe or it cleared too late or some such to conduct any more observations. That’s 78 out of 226 nights, or just shy of 35 per cent! So, more frequently than one in every three nights proved profitable. But I suspect the figure is nearer 40 per cent.
How do these data resonate with the above statements?
They don’t, do they?
Get yer logbooks oot……lemme see yer logbooks.
Sheer dumb luck?
Don’t give me that either!
I don’t believe in sheer dumb luck. Nor do I spend my precious time haunting telescope forums, you know, drooling over this instrument or that.
Nope; I’m an observer!
So I just go observing lol. You know, actually looking through my telescope; it’s not so hard is it?
Anyone with a deep enough interest in such things would quickly draw the same conclusions, at least on the British Isles.
Do I believe these findings are unique to Britannia et Hibernia?
Why should they be?
Surely, most of these observations were conducted during warmer, more settled spells, like in Summer?
Nope, computer says no! Check my logbooks!
Good spells occur in all weathers, from freezing cold nights to sweltering hot ones!
Have these data any historical precedents?
See my up-and-coming book, Chronicling the Golden Age of Astronomy, for a full disclosure.
If you take the time to examine the frequency of key historical figures who loved the night sky, you’d find fairly similar results in the literature.
How do I know?
I’ve studied those historical cases.
Phew! Quite a rant there!
But better a rebuke than faint praise eh?
Now, shall we get down to business?
Plotina; the author’s ultra-portable 130mm f/5 Newtonian sampling the skies from the southern Lake District, Cumbria, England.
A 5.1″ f/5 Newtonian was transported in its custom aluminium case to a site in Southern Lakeland, Cumbria (Latitude: 54.5 degrees North) to establish whether conditions were good enough to resolve a number of test double stars and to more generally assess the seeing and transparency at this location. The success of this modest ultra-portable instrument at various sites within the UK and Ireland has been truly remarkable, so much so that this author has totally abandoned more traditional instruments such as Maksutovs and refractors in favour of this small Newtonian to pursue all areas of grab ‘n’ go amateur astronomy. As explained in a number of previous blogs, the telescope sports a significantly greater aperture (130mm) than your run-of-the-mill grab ‘n’ go telescopes. Possessing a high quality optical flat resulting in a modest 27 per cent (linear) central obstruction, it is significantly smaller than all commercial catadioptrics and sports very high reflectivity coatings that produce bright, crisp images, very comparable to an equivalent sized refracting telescope. In addition, its relatively low mass and open-tubed optics ensures that it cools more rapidly than a similar-sized refractor or catadioptric.
During the trip, just one evening turned out clear, namely the night of Friday, August 10-11 2018.
Mostly clear with some patchy cloud. Temperatures were cool (12C), with a brisk south-westerly breeze, which continued to gust for several hours, abating almost entirely by local midnight. Transparency proved very good and although there was some light pollution owing to neighboring mobile homes, the sky was good and dark. Indeed, I judged the site a little darker than at my rural observing site in Scotland, with the northern Milky Way seen more prominently, snaking its way from northeast to southwest. The northern and eastern sky was especially dark, prominently revealing the majestic constellations of Cassiopeia, Andromeda, Pegasus, while high overhead lay Cygnus and Lyra. The site had a good view of the southern sky, with Aquila and Delphinus situated very close to the meridian. Two bright planets graced the southern sky low down, a dull yellow Saturn and further east, brilliant red Mars.
The telescope was precisely collimated using a good quality Chesire eyepiece and left to cool for about 20 minutes, with the open tube pointing straight into the prevailing (south-westerly) winds at the site. A working magnification of 260x was adopted to examine a number of test double stars. This was achieved by coupling a 7.5mm Parks Gold eyepiece and Meade 3x achromatic Barlow lens.
For widefield sweeping, a 25mm Celestron X-Cel LX was used, deliverng a power of 26x in a 2.3 degree true field. Higher power deep sky views were enjoyed with a 5.5mm Meade ultra-wide angle ocular which yields a power of 118x in a 0.7 degree true field. Mars and Saturn were observed at a power of 177x (using an 11mm eyepiece and 3x Barlow), which proved more than adequate, as both orbs were situated very low down in the southern sky around local midnight.
The test double stars were chosen for their easy accessibility as well as being progressively more difficult;
Epsilon 1 & 2 Lyrae
Lambda Cygni (examined at 354x using a 5.5mm eyepiece coupled to a 3x achromatic Barlow).
Double Star Results:
The first five test systems produced text-book perfect splits at 260x, the components being very cleanly resolved, and the individual stars presenting as perfectly round Airy disks with a single but rather subdued diffraction ring. The sub-arcsecond pair, Lambda Cygni, revealed its near-equal magnitude components as ‘kissing’ at 354x. You can’t do that with a 4-inch refractor; see here for just one example.
Additionally, the wonderful triple star system, Iota Cassiopeia, was examined later in the vigil, when the constellation had risen higher in the northeastern sky. I was rewarded with a perfectly resolved rendering of all three components at 260x using the 130mm f/5 Newtonian.
Despite enjoying just one clear night at this site during our short vacation, I achieved what I have come to view as fairly typical results for many locations in the British Isles. The telescope was able to deliver excellent high-resolution results on these test double stars. As stated earlier, I do not especially attribute these results to serendipity. Indeed, I have come to expect such results when conditions are reasonable at many sites within the UK and Ireland. Such results can easily be achieved by other observers using the same (read modest) equipment with just a little attention to detail; adequate acclimation and close attention to accurate collimation, which can be executed perfectly in under a minute. I would encourage others to test these claims so that these results become as widely known as possible.
Newtonian telescopes will continue to be my instruments of choice to observe such systems in the future, so as to help dispel a particualrly virulent myth that has arisen within the amateur community; a myth born out of ignorance and old fashioned laziness. Such a myth is plainly false and will allow many more observers to pursue such targets with unpretentious instruments that are very reasonably priced.
Observing the Planets:
Although certainly not a dedicated planetary observer, I have come to appreciate the very good views of Jupiter in recent apparitions using the 130mm f/5 Newtonian. During this vigil, my family and I enjoyed very nice, crisp images of Saturn with the telescope at 177x. Despite its low altitude in the southern sky, the planet revealed its glorious white rings with the Cassini Division being plainly seen. Some atmopsheric banding was also observed but, being much farther away, these features are much more subdued than on mighty Jupiter.
Mars was examined at the same power. This was actually the very first time the planet was observed telescopically during the present apparition. The view served up by the telescope was shockingly good and to be honest, not at all anticipated owing to its even lower altitude near the southern horizon. First off, I was amazed at how large the planet looked at 177x (a rather low power for a 5.1″ telescope on such a target generally). Though the image was roiling in the perturbed atmosphere near the local horizon, I was able to make out some dark markings on the planet as well as a rather subdued southern polar ice cap. I was aware that the planet had recently experienced a planet-wide dust storm that all but occluded many of the surface features but I was pleased to see that, while much dust was still present in the atmosphere, it was clearly settling out at the time the observations were made. Mars was a big hit with the family; its large size and great brightness to the naked eye being a lively topic of conversation with my wife and sons.
Into the Deep Sky:
Plotina is a step above the rest of the grab ‘n’ go herd with regard to deep sky observing. It’s highly efficient 5.1″ primary mirror collects enough light to put it in a different league to 90 and 100mm refractors.
How do I know?
I’ve done extensive tests with a 90mm Apo (shown below) and my notes show that double stars hard to see with a four inch refractor are easier to see and resolve in the 130mm reflector. It’s not rocket science!
Faster, cheaper, better: The author’s 130mm f/5 modified Newtonian( Plotina) enjoying crisp, bright terrestrial views and in a completely different league to a 90mm f/5.5 ED apochromat(left).
With the glorious return of true darkness to northern British skies, my first port of call was the endlessly glorious Double Cluster in Perseus. This is where the 25mm Celestron X-Cel LX eyepiece really shone through for me. I don’t know if you’ve ever held on to an eyepiece because of how well it frames a deep sky object, but this ocular delivered an absolutely beautiful, expansive view of the famous open clusters. It’s very comfortable 60 degree AFOV delivers a true field of 2.3 degrees at 26x, centring the clusters perfectly in the middle of the field and showing just enough of the rich stellar hinterland to render the experience particularly memorable. The perfect achromatism of the Newtonian delivers the pure colours of the white, yellow, blue and ruby coloured suns decorating these wonders of nature, each of which are located over 7,000 light years away. I stared at these clusters for a full 10 minutes before dragging my eyeball away!
Next, I pointed the telescope into the heart of Cygnus and drank up the sumptious views of the northern Milky Way, moving the instrument slowly from field to field in awe of the sheer number of stars this wonderful 5.1-inch pulled in. Sometimes deep sky observing is not about seeking out any particular object; for me, it often involves just sweeping the telescope through an interesting swathe of sky, sitting back and enjoying the visual sensations that bring joy to the eye-brain.
My telescopic sojourns eventually took me into Vulpecula, where I quickly chanced upon Brocchi’s Cluster (Collinder 399), otherwise known as the Coathanger, owing to its extraordinary configuation of half a dozen stars arranged just like its common name suggests and spanning over 1.5 degrees of sky, which was easily handled by the 25mm Celestron ocular.
Skies were good and dark enough to observe a number of planetary nebulae in Vulpecula, Lyra and Hercules and for these, I switched out the 25mm ocular for the 5.5mm Meade Ultrawide angle delivering 118x in a fine 0.7 degree true field. Easy to pick up in my 6 x 30mm finder as an 8th magnitude smudge, the 5.1-inch Newtonian delivered an awesome view of M27, the famous Dumbbell Nebula, its enormous size occupying a space fully a quarter the size of the full Moon. I find such structures haunting in the telescope and a kind of shiver went down my spine as I studied its enormous bi-lobed morphology alone in the dark (the wife and kids having now retired for the night). Moving west into Hercules nextdoor, I sought a spot about 4 degrees northeast of the fairly bright star, Beta Herculis. With the generous, wide field of the 5.5mm I didn’t have to switch out for a lower power eyepiece to find the lovely 9th magnitude planetary, NGC 6210. The telescope made light work of picking up its distinctive oval shape and its soft bluish hue. Finally I ventured east again into Lyra, where the telescope made light work of picking up the endlessly interesting M57, the famous Ring Nebula, easily located smack bang in the middle between Beta and Gamma Lyrae. At 188x, this planetary looks big and bright with its inner and brighter outer structures showing up well. It’s amazing that this luminous smoke ring in the August sky is estimated to be a full light year in diameter!
Having studied the bright and comparitively huge globular clusters, M13 and M92 at home in Scotland with my 12″ f/5 Dob, I was impressed at how well they presented themselves in the little 5.1-inch lightcup at 118x. I was in for a bit of shock though when I eventually tracked down M56 in Lyra, located roughly half way between Albireo and Gamma Lyrae. In the 5.5mm eyepiece, this globular was considerably smaller and fainter, looking more like a nebula than anything else. When I cranked up the power to 177x, the view was little improved; just a bright but unresolved core with a smattering of faint stars hovering like little fireflies around it. The view in my 8-inch Dob is far better but still rather lacklustre. I find my 12-inch Dob to do proper justice to this cluster and its gorgeous hinterland of Milky Way stars.
I ended my vigil in the wee small hours of Saturday morning, August 11, with a ceremonial visit to M31 and its satellite galaxies, now riding about one third of the way up the eastern sky. To be honest, galaxies never do much for me and I don’t really understand why folk in possession of larger instruments want to look at them in very small telescopes. Some say it’s heroic and admirable to do that kind of thing but I think it’s bordering on nuts. Why struggle to observe such faint fuzzies when you can more easily study them in larger telescopes? Anyway, the decent light grasp and expansive 2.3 degree field of my new Celestron LX ocular delivered a sterling view of this showpiece object of the autumn sky.
It was good to get away; our first visit to the beautiful Lake District. But all good things have to come to an end I guess.
The author did not emerge from pond scum and cannot for the life of him understand why anyone else would have such a low opinion of themselves. Such are the false fruits of evolutionary ‘science.’