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Old 10-11-2018, 09:29 AM
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Slawomir (Suavi)
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Join Date: Sep 2014
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Quote:
Originally Posted by Andy01 View Post
Hi folks,

I'm using a QSI683 wsg8 and recently had a go at using Astropixel Processor. Very cool software indeed.
APP allows the user to load lights, darks, flats, dark flats, bias or masters of each of these in any combination.

Some users are recommending using bias instead of dark flats - which I understand is very convenient.
Now I'm not looking for a very technical answer, I just want to use what works best! Usually I take lights, darks, flats & dark flats, but no bias.

So my question is - should I be using Bias or Dark flats? What's best?
Bias or dark flats or both?

cheers
Andy
Andy, I think it will be best to calibrate a dataset with both methods and measure and compare the results. But I suspect that differences will be negligible. Having said that, I feel that darks would be worth trying, given that there is a good number of them in order to eliminate any external signal such as cosmic rays etc during stacking.

With my camera (ICX 814), I found that SNR decreases slightly when I use a good number of darks for calibrating up to about 100 15-minute narrowband subs, but when stacking more than 150 15-minute narrowband subs, SNR improves slightly when calibrating subs with a good number of darks. I suspect this is due to a fixed spatial camera noise. Visually, there was no noticeable difference though, no matter how hard I looked.

Given such low dark current for my camera, which only shows a just measurable improvement when using darks for 40hrs+ of data, I do not bother at all with darks for calibrating 10-20s flats (for narrowband filters), since, from what I investigated, using 50 or so darks instead of hundereds of bias frames would make master flats a tiny bit more noisy.

For calibration, I use 250 bias frames and aim for at least 600,000e for master flats.

Last edited by Slawomir; 10-11-2018 at 09:45 AM.
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