Captain Scarlet

A handful of things that “are what they are” (or were, not necessarily all good), because of Astronomy: GPS; The fact that the Sun is at the same place in the sky at the same date&time every year; Various Empires, owing to the fact that a principal skill-in-trade of a ship’s captain 2-300 years ago was astronomy and spherical trigonometry; Winston Churchill’s escape and navigation from PoW camp in Pretoria to the coast - he said he used Orion as a guide; Of course those things aren’t why I and likely you do astronomy. I do it because it boggles my mind to be able to observe such vast differences in scale, and such huge amounts of “stuff” just hanging out there in “nothing”, so easily with merely some good engineering and curved mirrors*. Such beauty. Good, thought-provoking question! Magnus *some refractors aren’t bad either

Assuming the pairs of vanes are parallel, you’ll get just 4 spikes, but they will be “doubled-up” in intensity over single vanes. If they’re not quite parallel, you’ll get 4 pairs of spikes, with each pair annoyingly close to each other but distinct. Stu’s point about the single adjustment bolt is fair too: unless you can absolutely guarantee the mirror is perfectly positioned on the holder and square, you do need the extra degree of freedom provided by another bolt. 3 is actually overkill, 2 I’d say is a minimum. M

… something like “the artist formerly known as …” 🤣

Part of my initial (misguided) motivation for removing the baffle was to reduce the Central Obstruction to an absolute minimum. It was only later that I realised that the CO% was actually defined by the (unnecessarily wide) retaining ring for the primary mirror. So the baffle can be anything up to that value without spoiling things (meniscus-refraction adjusted). With the baffle completely removed you can see directly from the front of the scope and see light past the visual back, bypassing the secondary-mirror path. That should not be "allowed". In that configuration, looking at a bright object like the Moon will cause all sorts of serious extraneous light problems. Part of the purpose of the wider baffle therefore must be to block off that direct line of view through the VB. M

I did remove the glass, though I'm not sure if I documented it. I pulled off the baffle because it was seriously off-centre, but that in itself didn't require wholesale removal of the glass plate IIRC. I did eventually decide though to check that the clips retaining the glass in place were not "metal clip directly on glass", and found that that was in fact the case, so I did remove the glass to insert thin pieces of electrical tape under the clips. Recollimation was fine. I think all the surfaces at that end are spherical, and there is very little scope (apols for pun) for lateral movement of the glass, so the process of glass-removal and replacement is pretty forgiving. The thing you should take care of, if you are concerned, is to ensure the central reflective spot goes back in properly centred. I'm not actually sure how much care they took in ensuring that at the factory anyway, given how badly my baffle had been placed. All in all, you should be fine I think. The glass is coated with SiO2 (i.e. Quartz crystal, very hard indeed) so will be extremely scratch-resistant. I re-glued and removed my baffle (using Acetone) about 4 times I think before I was totally happy. Use superglue, it's totally soluble in Acetone. Good luck and keepus informed! Cheers, Magnus

I guess taking a hack-saw to the back of the tube would be out of the question for such a rare and valuable beauty 🤣 ?

… and I’m on your first! 😁😉

Here’s my 200p on a skytee2 … the saddles are upgraded to the ADM ones, though it is on the original Vixen-type dovetail on standard SW rings

This I am looking forward to...

I recently bought as a present for a helpful neighbour a pair of Nikon Prostaff 3s 8x42. I specifically chose them for their wide FoV and when I tried them out I could use them easily: I require long eye relief and use specs when using them. I’m used to Leicas, having 3 pairs, and these were not disappointing at all in comparison. M

Haha I’d have to add something, all I’ve done so far is find ROR’s regulatory filing and more or less copied that recipe. Perhaps an extra drop or two of “Eau de Magnus” to make it uniquely mine. Yuck.

I've just got around to finding out the IDs of the stars in the field: I'd made a note of what it seemed to be its match in brightness. Through my 8" and Nag 31, it seemed the same as HD 175919, which is mag 8.54 according to SIMBAD. This would've been around 0130 0100 this morning, 14th June. Quite fascinated to have witnessed something unusual. Cheers, Magnus

Amazingly different from last night. Barely detectable with my 15x56 bins. Whereas last night it was in a par with the 3-star asterism to the North.

I got my 62mm spotting scope out today during the day and put a baader solar filter on the front, which I’ve had for a year but never used, until now. That feature you point out was amazingly clear this afternoon, had rotated into view, and had real depth to the “hole”. Amazing, actually. Is it a sunspot?

What else is there to do on a lousy weekend like this 🤣☀️

After spending my observing session last night trying to navigate from the Coathanger to the Nova in Hercules (/Aquila) with my Skytee2 carrying a SW 8" newtonian, and eventually succeeding, I thought I might share a number that I wish I'd known last night. I was able to find the Nova very quickly using 8x binoculars plus @JeremyS's chart of the locale. Knowing that it was a bit over 7 degrees "mostly right and up a bit" from the Coathanger, I simply panned right just over a full binocular FoV and there it was. Through the eyepiece of the Newt, it was more difficult. First I had to note which direction the slo-mo knobs turned the mount, and I also had to judge how far to go. At higher magnification than the bins, with stars racing across the view and with one axis "reversed", it was quite tricky. Knowing the angular distance between the objects, if I'd known the "angular distance per full turn" of the slo-mo knobs, I would've been able to "fly blind" to the general vicinity with some confidence and pan around from that point. I did find it eventually, but knowing that number would've saved me some time. It should really be stamped or printed on the mount somewhere. I spent a pleasurable part of this afternoon with my collimation laser measuring distances between laser-spots on my living room wall. Any way, the Magic Number is ... ... ... 2.5 degrees per full turn on both the az and the alt axis. (perhaps this is well-known?) Cheers, Magnus

Just got it myself. Started at the Coathanger then one full viewfinder right in my 8x56 bins gets me more or less there. M

I’ll have a go at it myself tonight, just setting up for a session anyway

2-3 years ago I acquired a solid-tube SW 200p f/5 newt. It seemed in good condition and I have enjoyed using it. However it’s not been without some problems. The geometry was all wrong: the position and the size of the secondary mirror means that the secondary is significantly undersized. IE that the converging light-cone is bigger than the outside edges of the secondary. It means that the scope is acting not as a 200mm scope, but rather as a 178mm (by pushing the primary back as far as possible, and the spider and focuser as far "up" as possible without surgery, I've eked out another 5mm of effective aperture). Its also very "non-stiff", requiring recollimation of the secondary tilt for any big change in altitude. Anyway, the purpose of this account is not to address those, but rather to talk about how dirty it's been, and how I've cleaned it. When it arrived, it had rather a dirty primary mirror, well beyond my own criteria for requiring a clean. Lots of dust of varying sizes, but also a layer of something very fine, causing a marked dullness. So I cleaned it according to my method then, which was simply soaking it for a while and slooshing it in detergent and warm water, and using many cotton-buds to gently wipe the surface. What emerged was undoubtedly better, but that fine layer was mainly still there. You could see some evidence of wiping on it, but it was barely affected by my clean. I ignored it and have used the scope many times since. It’s given me much pleasure. However, a year or more on, and I’ve decided to give it another go. It’s acquired enough other dust and crud to need a routine clean anyway. In the pictures below, you can see the not-removed fine layer with its wipe-marks from the old clean under the dust. I now clean my mirrors differently. I soak and sloosh in warm detergent-water, as before, and vigorously run warm water over the mirror to lift and rinse off actual dust particles. But I have made up some home-brew ROR (Residual Oil Remover), and my next step is now the “fingertip method”. After doing this to my mirror yesterday, using this method with my ROR, I thought “nothing will survive this combination of solvents”. Final rinse is first with softened water from the tap, then a pour of de-ionized water, and finally a sloosh with laboratory-grade purified water. Well the mirror emerged apparently very clean, EXCEPT FOR THE FINE LAYER. It had made not a bit of difference to that, it was still there! I had as a “target” the bits of the mirror which had spent their lives under the edge-clips: they were pristine bright and shiny, and by comparison the rest of the mirror was not! I started over again, this time using a little more fingertip-pressure. Still no difference. I had one weapon-of-last-resort in my armoury: pure Acetone. This time I used a “wad”, a rolled-up piece of kitchen-cloth dabbed in the Acetone. I tested it first on a tiny section of the mirror just next to one of the mirror-clip “clean bits”. It worked! So using @markse68 ‘s method of successively dabbing, wiping, and snipping the rolled-wad (snipping to remove the contaminated end), I wiped the whole mirror in pure Acetone. The snipped-off bits when discarded were rather dirty! Remember this was AFTER doing a “normal clean” 2-3 times! Then more final-final rinses in my succession of water-types. I was very happy with the end result, and the pictures below should show the difference. To be sure, you can still see evidence of the contamination remaining, but the vast majority has gone, and the pictures do I think show a marked difference in contrast. When taking them, I tried to use identical exposure settings and I processed them out of the camera using the same “load settings” for each pair of pics. As for what the contamination was (is), I have no idea. My theory is that some previous owner was a smoker. Anyway, I look forward to trying it out, perhaps even tonight. Cheers, Magnus Before and after, from the side. Note the streaks on the "before" and the small amount remaining after cleaning (in a radial pattern). Not also the difference in contrast of the window-frame behind (the bright white spots on the clean pictures are spots of water, lab-grade-purified, as-yet undried): From directly above: And my control, giving me an idea of what I was aiming for:

I have exactly that WO 45 degree erecting diagonal and IMO it’s very good. I’ve had it for instance in my Intes M603 6” Mak looking at Hooded Crows on a post at about 60m distance, and the image quality seemed every bit as good as another scope I had alongside the same day: my Kowa TSN 883, which by all accounts is the match of the best spotters from Leica and Swarovski. the only “blemish” in that erecting diagonal was when looking at Vega one time, there was a diffraction spike from the “roof” of the prism. But I think that’ll make no appreciable difference for daytime use. Cheers Magnus

Yes those were exactly the ones I was looking at too. Wiki says they are evident with the sun between 6 and 16 degrees below the horizon … at the time I was looking the sun was about 10 degrees below. But I still have the same question as @Stu .

You learn something every day. I had no idea Noctilucent Clouds needed milk 🤣 Seriously though the first I ever saw were also while looking at the comet June 2020, and last night also 10:30pm I saw the same. Magnus

Thin cloud with occasional gaps for me. I managed to use the cloud as a sort of exposure-reducer and used my DSLR and 400mm lens to get this: Cheers, Magnus

About the same to me tonight through my bins just now as HD220102, which is 6.6 M

Still on the subject of Glaswegians I assume? 😉