alacant

Phew. Amazing effort. Alas my mosaic expertise runs only to a two frame image of the moon with an old orange tube Celestron. Nine panel without craters, I'd stand no chance! Not sure where you are, but it's quite well positioned ATM from 38N. Do keep us posted.

Hi everyone I'm always disappointed with this region. I thought more data would help, but disappointingly, adding more frames on night two gave very little extra; maybe a little more detail emerging in the spirals, but little else. I suppose that with an aperture of only 70mm, I ought not to be expecting miracles, but seven hours to get only this? We've a visit due from a Hyperstar. I'm gonna see if I can get my hands on that and compare. Tips, advice and -especially- your examples of this area of the sky most welcome. Maybe you've already tried with a Hyperstar? Even better, as I've zero hands-on with them; disaster waiting to happen territory. Thanks for looking. ubuntu 22.04 siril 1.3.0a st 1.9.565 dt 3.8.1

+1 @OP: Perhaps the best (only?) way to make a decision is to go along to a nearby astro club [1] and see items you're considering first hand. The members will be only too pleased to let you have a go with stuff gear you're considering. Between them, they'll have it all and it could help you avoid making an expensive and frustrating error. Cheers and HTH [1] Just remember that at astro club, everyone knows the best setup. For everything😉

Hi To enable us to help, we really need to see where the star is in the frame and so be able compare it to others therein. Maybe post -links to- example frames along with detail of mount, guiding, cc, how the guide telescope or WHY is mounted... Cheers

Hi and welcome Llinks to each cr2 may help us diagnose. Cheers

Hi and welcome Astro in Spain is exhausting. Just pray for cloud so you can occasionally get a good night's sleep 💤 Cheers

No, no. You must not do that. Chalk makes dust which could get onto your lens. Otherwise, good advice😉

Hi In Spain, maybe call Luis at str-astrum who may be more knowledgeable as to your climatic conditions. FWIW, for cooled CMOS here in Alicante, we've standardised on -5º all year round. In summer it's not easy maintaining much below -10º anyway and the benefit it brings is negligible. HTH

Hi I don't think a change of glass will make much difference, but a triplet may. Ideas. Use a: focus mask to get you close to focus, then remove it. Use live view to move away from that focus point until the blue halo is reduced. reflector #8 and correct the colour cast afterwards Or just mask and reduce it:

Hi Siril flips the images. Is there any reason for not using Siril to process your cr2s from start to finish? Siril's banding algorithm is best applied after pre processing the fit sequence. You need only a flat frame stack which has had the offset subtracted. Details here. You are free of course to flip back or choose any orientation you like. Probably easier though to do it after processing. HTH

Hi everyone First night for ages I had a telescope to myself. In fact two. Cheepo specials; a gso203 and a Bresser 203. m106, ngc2903, m63 and m66, changing to the gso after 106. Forgot to take flat frames, so had to guess the camera angle for the Bresser. Hopeless. The only way out was graX's AI, which I really don't like. Ironically, I think it has the best background. Thanks for looking.

Hi Some stuff is difficult or impossible to describe in words on a forum. The in person person is at your local astro club. Any of the members would be only too willing to get you polar aligned and imaging. Probably in less than 5 minutes! Cheers

To reseat the front element, simply loosen its retaining ring until upon shaking the lens, you can hear it rattle. Now tighten the ring until the rattle just disappears. That should help with the astigmatism/gulls/birds. ISO800 is the optimum setting for low noise on the 18mp sensor.

As per our 700d -same sensor- and an old Takumar 135... Did you try the ISO800 5s f8 no drizzle idea? You might also try loosening and reseating the front lens element. Cheers

People seem obsessed with it. I image. To me, it's useless. Where I live, I can see the milky way. But if there's a moon, haze or I've been looking at my 'phone, I can't. I don't need a number to associate with these observations. But... Is it a 'good' night if I can see the milky way? No idea until I've assessed the seeing. If it's poor, no amount of Bortle is going to change it. Cheers and clear skies.

I suggested f8: 50/6 = 8 and a bit

Really? A step down ring to 6mm?

It gives you a circular aperture, helping control aberrations around stars, particularly those caused by the non circular edge of the lens diaphragm.

For example...

Hi No need to cut the spring. Simply remove it. That should give you the distance you need. To help you with the secondary, replace the hexagonal grub screw adjusters with M4 hex head bolts; much easier to take up the slack that way. HTH

Hi Still a little overdone perhaps. eos600d? So as a starting point maybe try: RAW, ISO800, 5s, f8, no drizzle; leave the aperture wide open and place a M6 washer over the front of the lens. Cheers and HTH

Excellent image. Loadsa detail you don't usually see. I'm absolutely useless with colour, but had a go HOO. It may help in controlling the red a little. Cheers **@stu: have you had a go at this with the same filter on your f4? Should be an interesting comparison.

Yes. My bad. I read that the 8" was f5 and the 12" f6. f5 is offset. f6 is much more central. But the method I gave to adjust the secondary is still correct; the secondary is both too far toward the primary and is rotated incorrectly. Cheers

Hi The main difference between f5 and f6 is that for the latter, you'll find the primary donut reflection will collimate almost centrally, with very little offset. You have it set (perhaps by habit?) more as if it were at f5. Primary visibility is not helped by the small secondaries fitted to sw Dobsonians. The fix is easy: 1. Move the secondary toward the open end of the tube a few mm. To do this, loosen the three secondary adjusters and turn the central screw clockwise. 2. With the secondary adjustment screws still loose, rotate the secondary until it appears circular. Relative to your photos, you'll need to rotate the secondary anti-clockwise. Repeat 1 and 2 until you can see the missing primary mirror clip. Now you will be able to complete the collimation Focuser? Be sure to read the common collimation myths and Seronik's no nonsense collimation guide. Note that the fast and slow photographs in the AstroBaby guide are incorectly labelled. They should be like this (you're aiming for the slow version): fast: slow: Cheers and HTH

Therefore, and as your images show, apart from tilt, you are too close. Can't recall exactly but we needed at least 58mm from the shoulder of the m48 thread. The m48 t-ring alone will give you 55mm. With your 2mm spacers that's probably around 57mm, but you're now at the safe thread limit. Baader give 57.5mm. Use 58mm as a starting point. The low profile t-adapter with a set of extension rings makes this easy. It removes the coma, but introduces astigmatism. If you want out-of-the-box-corner-to-corner over aps-c, perhaps consider the GPU. Cheers and HTH