Quote:
Originally Posted by luka
Russell, was your DSLR cooled? If not how long exposures did you do with it? Camera noise will become significant for exposures longer than few minutes.
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the camera was uncooled, I have a fast imaging system 12" f4 newt, before the light pollution filter I was getting 70 second exposures. with the light pollution 3 mins was pretty much the sweet spot.
for narrow band it depended on the object, faint objects were overwhelmed with noise especially if it was warmer weather.
7 min subs on a bright object
https://www.flickr.com/photos/803366...posted-public/
10 min subs for bicolour helix
https://www.flickr.com/photos/803366...posted-public/
30 min helix raw trial sub - not recommended
https://www.flickr.com/photos/803366...posted-public/
here is another effort that I really didn't succeed digging out any faint detail because of the noise
https://www.flickr.com/photos/803366...posted-public/
so pretty much you're ok if its not hot and the object isn't too faint and you don't go over 10 mins as long as you get a fair bit of data. this of course isn't very scientific but just how I saw it. keep in mind the amount of Ha getting through on your chip will be way less so you will have more of a noise problem for me if you were considering Ha.