Captain Scarlet

Not “a” 12.5 Morpheus but TWO! We went birding last year and he had them in his APM 45degree binoculars looking at Snipe IIRC. The vista as your eyes approached the eyepieces reminded me of approaching the liquid-shimmering barrier to the other part of the Universe in the film Stargate. Two pools of swimming contrasty brightness. Lovely views. Magnus

I just went outside ahead of an early night to throw out the used cat litter detritus over the wall into our next field. Reasonably clear, suddenly at exactly zenith a streak appeared, heading North East. At first I thought it was the ISS, it was just the right speed and brightness. But it seemed to be accelerating and just getting brighter and brighter. At about 45 degrees from zenith it turned orange/yellow/green and broke up into 6-7 pieces which carried on getting brighter until all finally exploding and extinguishing probably 10 degrees from horizon. Quite the most spectacular such event I’ve ever seen, whether meteor or satellite I don’t know. Seemed to end up over Cork or thereabouts. Magnus

Dave Hi that is a collimation-locking bolt. I also have a Skywatcher 12" cell, and I never use those locking bolts, actually: my springs are strong enough to hold everything in place as I move my scope around. Also, I am about to receive an Orion Optics 300mm mirror cell, so my SW cell will very soon be redundant anyway. Consequently, for either of those reasons, I'd be very happy to send you my locking knobs. Otherwise It would ve going to metal recycyling soon anyway. I believe I still have your address in my PM inbox from the RDF you took off me. Shall I post it? No charge obviously. Cheers, Magnus

They are very detectable indeed, especially M81/2 to the extent I can see one is round and the other is a sliver. M51 is a little less distinct, but a definite smudge and no doubt when you’ve got it. But I cannot get two cores through the bins. And that is handheld too, although sitting down, and with my 21.8 skies. I’ll try through my 10x50s tonight which should also be clear. M

A change in forecast caught me out, I had no time to set anything up so I took out my Kowa 88mm spotting scope with Tak 7.5 eyepiece giving 68x; and my 15x56 bins for a couple of hours. Jupiter had too much CA, sitting directly over a large house. Saturn much nicer further West, really quite sharp but 68x not really enough to get any real detail. Still stunning though. Mars rising with lots of CA and extremely red. Then sitting in a chair with the bins I hunted down M51, M81/82, M52, M31, M33, M38, Pleiades, Kemble's Cascade, Coathanger, and a nice binoculars-friendly double in the head of Draco, I must look that up (Nu 1 & 2 Draconis aka Kuma). And a few shooting stars, mostly fairly dim. Tomorrow's looking good too, so with forewarning I might get my 12" out. Cheers, Magnus

No probably not

Yes thanks. Although it’s usable the way I have it at the moment, when I go the FF route I’ll probably put the green focus unit back in but shorten the main tube by an appropriate distance.

I think it has to be done. I’ve just compared directly side by side the APM and the Evoguide, and the Evoguide is SO much more satisfying and contrasty to look through. Starizona here I come…

First night Light has yet to happen, it may well be tomorrow night though if the forecast holds. I have looked through it during daytime though, and while it’s a lovely wide-field view, very similar in quality to my Leica Ultravid 10x50 binoculars, the field curvature is severe. When focused for the centre, the edge is awful of course, but the edge is a lovely view when it itself is got into focus. I guess it’s a problem with very short focal length, the spherical nature of the field is that much more acute.

Very nice! Where was this, West End Green? Magnus

Or put them In your main “life” calendar. Shame to have to let down anyone having a wedding those days but priorities are priorities. M PS thanks for the dates 👍🏼

In principle that’d be great but Mayo’s at least five hours drive I think 🙁

I can't really see the diagram very well, but hopefully I can partly answer some of your questions. When you suggest placing the secondary "inside the light cone" I guess you're talking about the on-axis light cone, i.e. the cone formed by light coming from an object at the centre of the field. While it's true an undersized secondary will indeed "miss out" rays coming from the outside edge of the mirror, the same is not necessarily true for off-axis rays. Beyond a certain angle off-axis, light from the edge of the primary will strike the secondary and get reflected into your eyepiece or sensor. So your image plane will be increasingly "contaminated" by edge-of-the-primary rays the further off-axis you get. If you want to mask off the primary's edge, you will need to do it at the primary mirror itself. Sizing of the secondary is basically a choice between contrast and illumination: either using a small secondary (but still >= size of the on-axis light cone) to minimize CO and hence maximize contrast; or using a larger secondary to increase the illuminated field at the image plane at the expense of contrast. A visual observer would tend towards the former, AP-ers the latter. Either way there is no real argument to size the secondary smaller than that covering the on-axis light-cone. Meaning that you will always be dealing with a more or less oversized secondary. As for the correct placement of an oversized secondary, there is no real absolutey correct answer. Conventional wisdom suggests that a correctly-sized secondary will appear perfectly circular in perspective from the focal point. However, this is only true if the secondary is exactly the size of the on-axis light cone (i.e. not oversized or undersized). If either of those conditions is not met (eye not at focal point, or an oversized secondary), then the secondary should not necessarily appear circular, depending on your definition of "correctly-placed". There are two intuitively obvious approaches when trying to decide a "correct" method for placing the secondary. One (the easiest) is to place the secondary such that it, the outer edge of the primary, and the inner edge of the OTA (if visible) all appear concentric from a collimation cap at the focal plane. This intuitively seems the right thing to do, but in fact it yields a non-circular fully-illuminated field at the focal plane. The other approach is to start off with the requirement that the fully-illuminated field be symmetrical and circular at the focal plane, and sizing the outside edge of the secondary to coincide with the outer edges of the light cones that produce this circular field. The problem here is that the shape of the secondary will then not be the standard elliptical 1.414:1, nor should it appear circular from the central focal point. Note that I haven't yet mentioned "offset" here. Offset up and down the OTA sorts itself out when using the optical tricks ("make circular") to get the desired perspective view of the secondary from a collimation cap, say. (i.e. the focal point). Transverse offset does need to be calculated and built in to the transverse position of the secondary, however. The trouble is, each of the methods described above yields a different value for the offset. However, the differences between these alternatives are small and, in my opinion, negligible. So as long as the secondary appears _roughly_ circular from the focal point, and the outer edge of the primary and the tube edge also appear roughly concentric, you should be fine. Draws breath. Cheers, Magnus

Yes indeed @Gonzo0, I’m at the very southern end of the West of Ireland: very near Baltimore. If you’re going to be anywhere near I’d be happy to try to meet up. Weather of course is not so reliable though! But when clear, as you say, properly dark! Cheers Magnus

Do these count? I have yet to use them on the night sky, but hopefully not too long now. I got them for travel and for the coming gas giant/Mars season. Magnus

Very nice inspiring read. It makes me want to get a Mak out, neither of mine have seen the sky for a while now. Cheers, Magnus

It weighs 1.29kg, so a fair bit heavier than the 0.80kg of the APM 8x50 finder it’ll be replacing for my 12”. But the 12” comes in at 21kg so the odd extra 500g won’t matter much. It’s forecast to be reasonably still with clear patches tonight so hopefully I’ll be able to give it its First Light, mounted on the Baader Stronghold you can see I’m the pic. I’ll compare it directly to the APM too… M

I initially added this to another thread but on reflection the other (3-years-ago-last-post) thread was the wrong place to put it, so I’ve put it here instead… I bought a one of these Evoguide 50 ED guide scopes on here a few weeks ago with the intention of turning it into a super-finder. The original plan was to do some surgery, i.e. to cut off some tube and use grubscrews to re-attach the focus unit and a diagonal. But experimenting by simply slotting a generic SW 2” diagonal I had spare, I found that my Panoptic 24 sat in at exactly infinity focus. The problem to solve was that the female thread inside the 50 ED’s tube appears to be M53, and the small difference between a 2”/51mm nosepiece and a 53 thread does not allow for any adapter. Besides, none seem to exist. So I very carefully wrapped the 2” nosepiece in a few layers of plastic tape, screwed it in and it’s fine, pretty solid too. No actual surgery needed. 242mm FL and 24mm eyepiece gives me almost exact a 10x50 68-degree well-corrected finder. It certainly looks very nice at distant objects terrestrially. It’s not RACI, but I don’t mind that. But my neck does mind it not being RA. I can’t wait now to try it out on my 12” … I reckon I’ll get as much pleasure looking through the finder as I will through the 12” eyepiece. Well, nearly as much. Cheers, Magnus

… deleted and placed elsewhere…

Not only that but if it were on top you’d hit your head on it whilst lowering your head to the main eyepiece

Thanks … my next target, skies permitting

Unexpectedly clear, I umm-ed and ahh-ed and roused myself to whisk out the LZOS 105 and ayo2 to see if I could finally get the whole Veil in one field (I did!), and to look for the North America and Pelican Nebula for the very first time. Both with my Baader 2” Oiii. Both successes, using the Nagler 31 for 21x and nearly 4 degree field, but neither terribly impressive, there was a milky sheen to everything such that the MW, so impressive two nights ago, was rather washed out. I popped in the Ethos 4.7 for quick looks at Jupiter and Saturn at 138x and that was it. Two “ticks” but to be revisited on a more transparent night. The Veil-in-one-field was good though. And there were 2-3 serious flashes from over the hill towards SSE, which I looked up were some heavy thunderstorms just off the coast of Brest. Magnus

Out here in the West Cork coastal countryside, I have over the past couple of years become good friends with a neighbour who’s Swiss/German and spends 4-5 months of the year over here. He, and particularly his (Irish) wife have on several occasions mentioned in passing that if I were to happen to do a shared session they would be keen to attend. They love the night skies here - most Easters I can get 22.0 on my SQM-L when the MW is down - and she even mentioned that a semi-tutored tour of these skies was one of her “bucket-list” items. Crikey, no pressure then. It's been stubbornly cloudy and quite windy since the latest Moon-down half-month started, but from a week ago, the forecast for Monday 29th had stayed clear, and so it proved. Monday it was, and I asked them to arrive around 2130 while there was still a vestige of twilight left. As it happened there were four of them: they had their daughter and her husband with them, and as it turned out the daughter was the most impressed by everything she saw. Definitely a future Astro-convert. They arrived as I was still aligning. I had two scopes out, my 300mm OO/Helmerichs Newt on AZ-EQ6, controlled by the standard SynScan handset; and my 105/650 LZOS refractor on an Ayo2. The newt I’d pre-installed with an Ethos 13 giving 141x, and the LZOS was given my Nagler 31 for 21x and 4 degrees FoV. I’d attached my Nexus DSC to the Ayo2 but in the end it was used purely manually, as they arrived before I had a chance to align it, and I can appreciate watching someone else align is rather tedious! I set up behind the house, facing South to East to get some planets in. I told them I’d give them a tour of the best example I could find of each of the main types of objects we visual astronomers like to observe: planets (obviously), double stars, globular clusters, galaxies, open clusters. In the end I forgot planetary nebulae: next time! Being still twilight, I pointed the 300mm to Saturn. The seeing seemed quite good, and there were quite a few moons on show. Cue gasps of wonder, one after another as they took turns at the eyepiece. “It doesn’t look real, it looks like a cartoon”. Next, I explained a little about double stars, how beautiful they can be and how most are not just pretty patterns, but actually gravitationally-bound systems. So I showed them Cygnus, pointed to its head and said that star, Albireo, is also known as “The Jewel of the Sky”. They were amazed at the vividness of the colours, and appreciated the trick of de-focusing to get the colours even more clearly. I let it pass that in fact Albireo is not a gravitationally-bound double, merely a pretty alignment. None of them had ever heard of the term “globular cluster”, so I drew their attention to the central “keystone” asterism of Hercules, and both the younger pairs of eyes could see M13 naked eye. It was on the very edge of detection for me, helped by knowing exactly where to look. Again, at the eyepiece, sounds of OMG! And Wow! As they looked at M13 at 141x. Our next object-type was “galaxy”. We were going to look at M31, of course, and for this I put in the Nagler 31 to give us 59x and 1.4 degrees. By now the Milky Way was prominent, SQM-L showing 21.5, so I quickly described that looking at the Andromeda Galaxy they’d be looking at a “Milky Way type” galaxy, but from a long way off. That the bright streaks of the Milky Way were more or less the same thing as the view of M31 initially confused them, but suddenly clicked when I said that everyone knows what a tree looks like, but it looks quite different when you’re sitting on one of the branches. I’d warned them that the thing about looking at a galaxy through a scope was not the incredible view, merely a fuzz, but the thought of what you were looking at. M31 was duly appreciated. Jupiter was just about high enough to be worth a look, and despite some atmospheric CA some detail was on show, and of course all four moons. Similar reactions to Saturn, partly at being able to see any sort of detail on a planet, but also its sheer size took everybody by surprise. Open Cluster was next, and my example of choice was the Double Cluster. Having ascertained where it was naked eye, they appreciated the beauty of the myriad pinpoints against black and the variety of colours and brightnesses. Finally, after a quick return to more gasps at Saturn, I suggested we try for Neptune. I warned them that it wasn’t going to be spectacular, but it would just about be a disc, and just about appear blueish. Just to be able to say they’d seen it. It was found easily enough. And throughout the session there was a steady stream of meteors, lovely! I must say, a most rewarding session, even though I forgot any PNs. I wanted to show them the Double-Double too but that was nearly vertically up, and one of the party would not quite have reached the eyepiece even with my steps. I think I’ve definitely caused the acquisition of at least one scope, and when I get around to founding a local Astronomy Society, they’re definitely in. Thanks for reading, Magnus.

Set up early and ready for the first session, once again, in what seems like AGES. My neighbours expressed an interest so I’ll be giving a tour of the greatest hits, with the LZOS at 21x and the 12” at 150x-ish. Cheers, Magnus

Shock horror … it finally got delivered! VERY worn packaging. At the bottom of the lane again (not wet because there’d been no rain for 3 weeks) but it took 3.5 months, and a re-order in the meantime. So I now have lots of extra highly specific mostly Torx bolts with various lengths widths and heads. Always useful. Magnus