Well I finally got enough of the equipment that I need to do some prime focus astrophotography.
Tonight there is patchy cloud in Sydney (closest thing to clear skies I have had) and I figured that my first attempt wasn't going to be that good anyway, so I may as well set up and test it all out.
My first target is M42. It is a single 28 second exposure at ISO400 on the Pentax *ist DS. Probably needs to be better focused, or better polar aligning (still need the reticle for that).
Yep the mount has drives. Last night was really only a test as the clouds were around. Thanks for reminding me about the Hartmann Mask as I intended to get one, once I needed it.
Can I ask though, in the following image the stars are trailing, but not in a straight line. Can anyone explain why the trailing is curved and seems to jump into a different line anyway.
Daniel,
Congrats on a first shot. You'll see the feverish obsession grow more and more as you go :] .
Some thoughts:
the trails could be shifting because of wind? or as David says the mount itself.
Good drift alignment will make a big difference I have no doubt
you may want to check the obvious (i've ruined many a shot having forgotten to check the basics) like any cables dragging/getting caught up, check the balancing (some say keep it a fraction heavier on the part that is rising (be that the weights or the scope depending on where you're shooting)
you can make your own Hartman mask : http://www.iceinspace.com.au/index.p...63,187,0,0,1,0
looking at your first shot , you'll be there in no time
cheers
frank
Thanks for the advice, I think I may need to get a little checklist together to remind myself of all of the things you need to go through when doing this stuff.
Yes a reticle is on the shopping list, so some time soon I should be able to sort that out.
I use a remote switch, I wouldn't even bother without one; I shake waayyy tooo mucchhhh!!!
Daniel...
OK - because I get that star trail "kink" if I just press the button or use a cable remote.
I now use an IR remote that is set on a 5-second countdown - allowing the mount to absolutely stop shaking before firing the shutter - and there's no "tugging" on a cable..
Umm, so when I said a remote switch I actually meant the cabled version. The camera has a 3 second delay setting for the remote, but this doesn't actually result in any delay at all.
Can I ask though, in the following image the stars are trailing, but not in a straight line. Can anyone explain why the trailing is curved and seems to jump into a different line anyway.
Got stacks of similar shots too . I took the mount apart, degreased it, re-lubed it. That sorted out the wavy trailing. Once I had "straight" trailing I tried to balance the mount better. That took care of drift in RA. If you still get drift in DEC then better your Polar alignment, but it's more forgiving.
I actually plucked up the courage to follow iceman's guide on cleaning mirrors the other day . Pretty scary stuff but I think that maybe with a bit reading up I might be able to give your suggestion a go. It does seem that most people are doing this type of thing to their mount in order to get the most out of them.
Tonight I still used the 8" Newtonian at prime focus, but, rather than 1 28 second exposure, I thought I would give stacking a proper go.
Focus was better tonight and I mixed up the exposures just to see what would happen.
Exposures were made up of:
ISO400 - 5 second x 5, 10 second x 5
ISO800 - 5 second x 5, 10 second x 5
ISO1600 - 5 second x 5
The final stack was made up of 22 images in registaxx and I also did Histogram processing here.
Well...at least it is an improvement and any advice on how to get better data or process better is much appreciated.
:
nice image of the trapezium there well done 
. I took the mount apart, degreased it, re-lubed it. That sorted out the wavy trailing. Once I had "straight" trailing I tried to balance the mount better. That took care of drift in RA. If you still get drift in DEC then better your Polar alignment, but it's more forgiving.
. Pretty scary stuff but I think that maybe with a bit reading up I might be able to give your suggestion a go. It does seem that most people are doing this type of thing to their mount in order to get the most out of them.
