Captain Scarlet

They’re passive-aggressively enforcing no-mow-May on you. Insects are grateful 🐝 😁 M

Sounds as if you should do what I’m attempting to do … start one. To begin with you’ll be Founder, President, Treasurer, Secretary, only member 😂. My approach has been think of a name, get a little bit of infrastructure set up, i.e. a website and/or FB simply saying what it is and where and when you’ll meet up (perhaps a local pub with observing lawn out back, last Thursday each month say), distribute some flyers and tell anyone who’ll listen, turn up and accept the first couple of “meets” you’ll likely be the only person there. You may be surprised who comes out of the woodwork. Cheers, Magnus

Thank you all, that’s great, just what I need. What will go into my article will be the word “most”, as it’s for the benefit of people who share these skies here. For myself, I can easily see M1 in my 10x50s. Thanks, Magnus

I've been asked to write an astro piece for our local community newsletter, and one thing I want to touch on is equipment for prospective beginners. Binoculars are one obvious recommendation, so my question to experienced dark-sky observers is this: "Approximately what percentage of Messier objects do you reckon are detectable with 10x50s at a dark site?" Our skies here are 21.8, and I have measured 22.0 a few times with the MW out of the way on tryly transparent nights)?. I have a feel for what the answer might be, but I have by no means seen them all. Thanks., Magnus PS I'm also starting up an astronomy group/club/society - there are none here.

I would expect the effect on collimation of that tiny amount of lateral movement will be completely negligible, especially compared with the astigmatism you’d have from tight grubscrews. M

Those nylon grubscrews are there to constrain the mirror's side-to-side movement (using nylon rather than the metal of the clips themselves), but not tightly constrain. They must not be tight to the mirror's edge, they must be infinitessimally clear of the mirror, so the mirror is constrained, but not put under any pressure (even a little pressure causes astigmatism - my brother-in-law once asked me "why are the stars triangular?" when I'd made that mistake). What I do now is screw those nylon grubs in until they just touch the mirror, then unscrew about 1/8 turn. You may be able to feel a very small amount of "rock" as the mirror shifts when, say, you're carrying the tube out to the mount - that slight amount of movement is fine.

The whole point of the cell design is that the whiffle-trees (the three triangles each containing 3 nylon supports) have freedom of movement. The silicone prevents this and is unnecessary, indeed destructive to the whole purpose of a cell. I bought my 300mm cell a few weeks ago new from OO. There was no silicone, quite rightly. I bought my 200mm within a VX8, and the whole cell was slathered in silicone, top, back and sides. And whoever did it made a real mess. I dismantled it and removed all the silicone and it now behaves as it should. Aside from the difficulty getting the mirror out to clean, the cell is IMO a good design. Why they feel the need to silicone everything up I have no idea. Magnus

Yes I've done this a few times now with both my OO mirrors. I did consider cleaning them whilst still in cell, but decided in the end to completely remove it. Unfortunately yes you do need to completely remove the rear section by removing the collimation knobs. You then need to unbolt and remove one of the "clip units" (two bolts and possibly a grubscrew. With one clip unit removed, you can then remove the mirror "sideways". It needs great care, of course. Magnus Edit: I plan at some stage to grind away the top part of the mirror-retaining clips and replace with a more removable or rotatable pin arrangement, so that I can simply lift the mirror off vertically. I haven't designed it yet, but it shouldn't be too difficult.

Absolutely amazing. I remember your much earlier shots from a year or three back, themselves very good indeed, but my god you’ve kept learning and your stuff has become something else! Keep it up. Cheers Magnus

Paul so pleased for you to see that sort of detail in M51 and 81/2. If you could see spiral structure in M51 you should easily have been able to see the third part of the Leo Triplet. Is it possible you panned in the wrong direction from M65 & 66? I have done that before more than once. Having myself seen M51 from a dark place, I subsequently found myself able to see it from London albeit as a faint smudge, by knowing exactly what to look for and where to look relative to the two bottom “saucepan handle” stars of the plough. I did feel your joy from your report. Cheers, Magnus

Yes the change was certainly worth it. The Planet is far more stable and solid than the SW 2” tripod. As for tripod-strike, these pictures show that it’s not a problem for me, with my previous 300p, my current 300/carbon-tube, and my Stellarvue SVX140T. Though I did consider the extension pillar, so far it’s (just) not been necessary:

From the floor to the top of the head mine is 87cm, and 74cm between two the tips of the rubber feet. You’ll see from my photo that it’s not fully folded in, but I’ve adjusted my figures as if they were. Cheers Magnus

Yes just the same here actually this am

Just looking at Plato … I can get a few craterlets, what do you think?

Duplicate post

At the moment I’m unable to tell. Because of the very short eyepiece adapter, the eyepiece sits on the internal lip which prevents the nosepiece sitting atop the prism face. So it turns out that the critical dimension is the distance from the open end of the nosepiece to the eyepiece focal plane. As it happens, the Pan 24 has a very short nosepiece*. Those on all my other eyepieces, every one, are significantly longer. It’s lucky the one I really need to work, does so. But it does give me an excuse to take 10mm out of the middle of the tube at some stage. M * edit: the shortest of the whole TV range, it turns out, lucky coincidence for my 10x50.

Just under a year ago, I picked up an Evoguide 50ED, intending to use it as a super-luxury finder to go one better than the APM 50mm finder I already have, itself no slouch! It would mean that I could dedicate each to a scope and avoid too much re-alignment fiddling. Assigning the APM to my 200mm newt and the Evoguide to my 300mm newt. In theory, with my 24mm Panoptic, I'd get a 68-degree 10x50 finder. Of course, I knew in advance that this scope is designed as a guidescope not a finder, and it comes with warnings that it will not reach focus with a diagonal attached. This didn't deter me. If necessary and in extremis I could perform some surgery on the main aluminium tube and shorten it, though that would be saved as a last resort. Initially, I removed the green helical-focus unit and simply shoved a spare generic 2-inch SW star diagonal up the tube, taping it in place. I added my 24mm Panoptic. To my surprise, in daylight I did appear to be able to reach focus JUST ABOUT, but there were four problems: 1. it was UGLY, with a 2" lump jammed in to one end; 2. I had no convenient focus control, as I'd removed the helical unit; 3. Something I had not anticipated: severe, really severe, field curvature. A 16km-distant target (effectively infinity for a 242mm FL scope) at centre-field was lovely, easily the match of, say, my Leica 10x50 Ultravid binoculars. At the edge of the field, it was extremely blurry. If I re-focused to bring the edge into focus - crudely, by simply manually lifting the eyepiece out a bit - the edge became superb too, ruling out edge-aberration. 4. I only discovered this later using the Ugly Ducking on the night sky: it hadn't really come to focus during the day: my eye was highly stopped down, of course, being daylight, and I had obviously accommodated a bit - something I'm less able to do with my pupil fully dilated at night. I'd been following @markse68's very similar project, and seen that two modifications could solve all the problems. i. Baader T-2 prism diagonal, to screw directly onto the back of the OTA; ii. Starizona Field Flattener, made specifically for this scope, which also increased total available back-focus to 55mm, AND of course does what it says: flattens the field. The new diagonal and its low-profile eyepiece adapter arrived yesterday, I assembled it all and have just daylight-tested it. So far I couldn't be happier. I can achieve focus with an extra 5mm to spare. The field is now truly flat, an amazing difference, actually. Most importantly of course, it now looks the business. I can't wait to get it under the stars, and combine my 1830mm 300mm scope with a mega-wide-field well-corrected 242mm alongside. Cheers, Magnus

Two diagonals and an adapter. Dare I say it but sat next to the BBHS 2” mirror diagonal, the T-2 looks “cute”. The small diagonal plus adapter are the final bits for my SW EvoGuide 50 to make it into a luxury finder. And see what passes for delivery around here - some of them can’t be bothered to go up my lane. It was pouring with rain and luckily I saw the van down the road from the house. Magnus

Yes that’s true, but all told less diffraction though. A 4-vane spider in fact produces 8 spikes, but in 4 pairs which overlap/“double-up”. With a planet, for any given point on it the total amount of vane-induced-diffraction-softening from that point’s neighbouring “pixels” is reduced both by the one fewer vane and the fact of thinner vanes. I’ll probably start off by adding one vane with the original spider still in place, to compare spikes side by side

My own effort to reduce spikes/help local contrast has seen me buy some 0.2mm thick stainless steel sheet and I’ll get my local metalwork company to guillotine it into 15 or 20mm wide strips. I’ll also reduce the number of vanes on my 8” from 4 to 3. These will replace my current 4-vane spider whose vanes are 1.2mm thick. The idea is that fewer vanes will reduce total length of diffraction edges, and the thinness will make the spikes longer and fainter, throwing most of the diffraction far beyond a planet.

I believe @Stu got one, like the one in fig7 on that linked site, and recently inadvertently blind-tested it by being terribly disappointed by poor views he was getting of Jupiter in his 8” newt. He then remembered he’d left this mask on from a previous session, removed it, and Jupiter was suddenly much better. I’m sure he’ll tell the story more faithfully when he reads this, but that was the gist that recall. Magnus

Just ordered one myself on the strength of this thread. M

For a change it seems I’ve had a reasonably good run of clear nights lately, even if the last one a week or so ago, which I didn’t bother mentioning anywhere, was excellent transparency but terrible seeing. Last night promised something similar, and checking the Jetstream forecast I saw red/yellow just where I am at just the time I was due to observe. So my expectations were low. As it happened, seeing was rather good, excellent even, towards the East. Less good but still not bad to my West. I had planned to inspect Plato and its craterlets and see if I could spot the rille running down the centre of the Alpine Valley just nearby. I was able to see the craters lining one side of the Vallis Alpes, but the rille escaped me. I tried hard at various magnifications from 156x to 586x (mostly at 313x which seemed the sweet spot) but no joy at all. Plato similarly, although enjoyable, only gave up one of its internal craters, near the middle. I have seen 4 or 5 before but I can’t recall through which scope. I understand that there are plenty more tiny cralerlets that can show under perfect seeing and perfect scope? I vaguely recall @PeterW mentioning it. I run ahead. I’d set out my stuff, AZ-EQ6 and Stellarvue 140, whilst still light around 8pm. After dinner I went outside and noticed there was not a small amount of dew, all surfaces were wet. Luckily the scope has a very long dew-shield and the objective was, and remained, clear. I aligned the Nexus DSC on Capella and Algieba – Algieba is good because you know you’ve got the correct star as it’s an easy double – and decided to start off by going to my seeing-quality-meter, Epsilon Lyrae. My session a few days previously was so terrible I could not even nearly split the Eps Lyrae doubles. Tonight, though, was different. The Double-Double was EXQUISITE at 94x. Seeing to the East was clearly very good indeed. And my Nexus DSC didn't miss a beat all evening. I hopped over to the Moon, to the West, and as described above, couldn’t get full satisfaction, though it was enjoyable enough. That direction takes me over Baltimore village and harbour, and beyond it Sherkin Island and Clear Island, both inhabited. I wonder if turbulence in that direction will be a permanent “thing”. I could see transparency was slowly deteriorating and cloud blocks were starting to move in, so I decided to select some doubles from my SGL-gleaned list. First was Izar, easily split at 156x with the Delos 6 and more so at 313x with the DeLite 3. Next I chose Zeta Herculis, and again at 313x, dare I say, was also an easy split. Orangeish and smaller blueish IIRC. Nearly finally I went for Mu Bootis, aka Alkalurops. I’m not sure I’ve seen this system before, in some ways it resembles Epsilon Lyrae, except one “end” of the pairing was a single star, brighter than Eps Lyrae’s, and the other end was very similar to the Northern double of Eps Lyrae, an in-line double, the same separation at 2.something arcseconds, except dimmer. Very nice. For some reason I decided to finish off with the Ring Nebula, M57, to see if I could see a particular dim star nearby. Well, not only could I not see that star, the Nebula itself was extremely dim, to the extent I had to search hard and use averted vision to detect it as a Polo. I’m sure I’ve seen it bright and clear in a small scope before, so I put it down to increasing foggy haze exacerbated by a 78% Moon at 40-50 degrees up. That was enough, by now it was 1am and getting seriously cloudy. Normally I try to add pistures to illustrate, but last night I forgot. A very nice session, though, and the overall impression of “stars” through my scope was really something else, so I was very happy. Thanks for reading, Magnus.

For the recent strong display, last Sunday, I was ready and waiting outside once it had got dark and when my eyes had adapted was seeing very little, and about to give up, when the northern sky erupted into bright shimmering quite high-contrast vertical curtains of grey. I involuntarily swore out loud. Occasionally there were distinct hints of green. And this was from the very south of Ireland, my first ever view of the phenomenon. Being half Finnish, West Cork was not the place I expected to see it first. I grabbed my camera and took some 3-4 second exposures. The contrast to the naked eye seemed higher than in the pictures, but in grey. Magnus

Just in from what I expected to be a failed session. I’d checked the jetstream forecast and it looked as bad as it could be. Gratifyingly, seeing was quite good, better for various doubles to the east than for the Moon to the west. Good enough for zeta herculis to be an easy split at first glance through my 140. But not good enough for Plato to give up more than one craterlet. It just qualifies for a separate report tomorrow. Magnus