I thought I'd just pop this one onto the forum to encourage any
newbies who are just starting with AP, and are not yet familiar with
DSS etc: No processing other than increasing saturation a bit.
raymo
Thanks Peter and Dunk. I chopped off about the outer 10% to get rid
of the worst of the coma, and to enlarge M20 a little. The 1100D is
the best I can hope for unless I win lotto; actually it does all I need.
raymo
Wow, that's great. Much better than my effort at M20, which I've attached. Your's seems to have much less noise. Mine was 35 seconds through a Nexstar 8SE with a Nikon D90, like you I set ISO to 3200 but did no processing at all. Any tips from anybody are welcome.
Russell, most of your noise could be eliminated by dark frame subtraction, either in a camera setting or with a separate dark frame. I'm not sure which in camera setting it would be on the D90 though, but it would be something like "long exposure NR" or similar.
Thank you Chris, Russell , and Kevin. I posted it to show newbies that provided they can get reasonable polar alignment, they can get some
sort of fairly decent results from day one.
Russell, the 8SE, whilst being of the same aperture as my 8" Newt,
is much slower photographically, so will not gather as much data; also,
your exposure was a little shorter than mine. It looks as though your
focus is a little off as well. Incidentally, my image is one of 50 that were
stacked and posted here back in June. If you want to see the result of stacking
you can click on this link. http://www.astrobin.com/105011/
raymo
Last edited by raymo; 09-08-2014 at 10:11 PM.
Reason: more info
Thanks Kevin and Raymo, I will have a look at the camera manual re noise reduction, or possibly venture into the dark art of dark frames! I must admit that focus is a bit of a problem for me. What I do at the moment is line up on a fairly bright star, do a series of, say, 10 second exposures and adjust the focus after each one until it seems OK. Then use the finder to find my photo target and hope it comes out somewhere near the middle of the frame! I am sure there must be a better way though. When I get more time I will post up a few of my other efforts, any advice is more than welcome. I think I may have been bitten by the bug. Oh, I should say that the Nexstar now has a F6.3 focal reducer fitted and is now on an Alt-Az EQ6 for photography-which should enable me to increase exposure times somewhat, or I may explore stacking images when I have time to think a bit more about the concept. Thanks again for your advice and suggestions.
Does your D90 have Live View; if it does, just get a bright star on the
screen, magnify it 10x, and adjust the focus until the star is as small as you can get it. If it doesn't, a Bahtinov mask works brilliantly. About $40,
or download instructions from the internet to make one yourself.
Even at f/6.3 your 8SE is still significantly slower than my f/5 Newt.
raymo