I recently bought a home made equatorial platform from another iis member which has allowed me to take some 20 to 30 second exposures using my 8 inch gso dob with an afocal d400. For the most part I can only use about 50% of the frames I take but they seem to work out alright except for the blurring on the edges (I dont have a coma corrector or anything).
Any tips would be appreciated
The pics are the trifid, lagoon, omega, keyhole and eagle nebulas as well as ngc 6215
I'm not sure if these are full images or crops?
How many exposures have you taken for these images?
Anyway here's some tips:
1. Take flats to get rid of the vignetting. There may also be some other light interference? You can get rid of vignetting using gimp or photoshop - but that is harder and not as good as flats.
2. Take more exposures. 60 - 90 x 30 seconds is okay to start with for brighter objects, but you'll notice many of the great images are hours of total exposure.
3. You can use "lens correction" in gimp or photoshop to help correct the star distortion at the edges - but this must be done on an uncropped image.
4. Get the polar alignment as close as possible to avoid drift.
This will help to start with - then you can learn more about exposure times, processing etc.
Some of those were cropped but ngc 6215 wasn't. I'm not sure exactly how many frames I had for each one, I normally take heaps of frames (up to 100) but I can normally only use 50% of them as the platform is just a little bit uneven in the way it tracks.
I'll try using flats, I tried some tonight using a white shirt stretched over the scope and pointing it at a lit room but that didnt really work. I read somewhere that you can use a white computer screen so I might try that tomorrow night.
