Thanks Greg, Lachlan, David and Adam.
Lachlan: re collimation, I use the "hall of mirrors" technique
https://astrojolo.com/gears/ritchey-...e-first-light/ to make the primary and secondary parallel at any point in the procedure. I also have a Glatter laser with a holographic attachment which generates concentric circles to line the primary up with the centre of the tube.
I have not found a good guaranteed technique, but a combo of the straight laser, the holographic laser and the hall of mirrors seems to get close with some iteration, swearing and crossing of fingers! Often never quite clear whether to adjust primary, secondary or the collimation ring I have on the back - not helped by the lack of a centre spot on my secondary. But make small changes and check. The main source of error is the laser not being central in the focus tube, and I try to guesstimate/fix this by using my rotator to spin the laser round and make sure it doesn't move. Or if it does, the centre of its circle is where the focuser is really pointed.
Finish off with a test on a defocused star and maybe a very slight tweak of the mirror to centre everything up.
Quote:
Originally Posted by Dave882
Both those images are fantastic! Particularly impressed with the hamburger and the detail you’ve revealed both in the body and tidal stream. Very hard to do well like this especially without dark sky!
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David - the skies were very dark. Just not great seeing on 2 of the 4 nights and some dodgy flat frames made it harder than it should have been.