Ineffective Flat Frames

[Keshdogga (Casey)]

Hey all,

I've been having trouble with dusk and specles on my CCD and telescope and to combat it i've bought a light box to take flat frames with. I get great big transparent blobs all over my image that i thought flat frames would retract however It just doesn't seem to be working to the fullest extent. The blobs are only slighty reduced.

I'm guessing that i'm taking flat frames with the wrong exposure time and i would really like to hear another person's experience with light frames.

Also, seeing as I use Deep Sky Stacker to combine images, is the appropriate time to combine the flat frames in the initial image stacking process or is it done after the image is combined/post processing?

I will post some photo's later today to make what i'm saying more clear.

Cheers,
Casey

[Poita (Peter)]

Have a quick read here, and see if you are missing any steps.
http://dasflatframes.blogspot.com.au

[mithrandir (Andrew)]

There's a tutorial using Nebulosity here. The full manuals are on Craig Stark's web site.

The order of the steps is the same for other programs.

[Peter Ward]

I wrote this years ago, but the principles are still valid.

The link is here

[Keshdogga (Casey)]

Thank you all very much, I have just found out how to see the ADU values for an image in MAXIm DL. So if i've got it right, my SXV H9 has a well capacity of ~27000 electrons (the starlight website says >27000) and a gain of 0.45 ADU which means i'll need to be taking flats with at least 20000 ADU but preferably something around 40000 ADU. Sweet