i used icnr before but this made no difference, just took longer.
Quote:
Originally Posted by [1ponders]
If you take your first image and the temp is 24deg and when you take the last image the temp is 18deg then the last image will have half the dark current (noise) than the first. If you start taking darks then and by the time you finish taking the darks the temp is 12 deg then the last dark will have half the dark current than the first and only 1/4 the dark current the first light has. It is almost impossible to get accurate dark subtraction in this situation. Unfortunately this exact situation is not uncommon in SE Qld at this time of the year. You start taking images after twilight and finish taking darks 4 hours later.
I used to be a strong advocate for taking darks after lights. But I consistently get better result using ICNR now. If the temp is stable within a couple of deg then later darks can work well, otherwise I would strongly recommend using ICNR.
The biggest problem with ICNR is the loss of time collecting Lights. It takes two hours to collect an hours worth of lights. As with most things, its a trade off. If you have plenty of time then ICNR, if only a small window then darks later.
Mind you I'm not convinced that this is your problem, but trying this method may eliminate one factor that could be causing you issues.
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