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I’ve never got along well with flat frames, I’ve always had trouble with getting the levels just right. It’s tempting just to fire it all through PixInsight and let the background extraction tools take care of it, but it doesn’t get better than having good calibration already done, espacially when you have light pollution to battle on top of that.

So, I thought it was time to get to grips with this part of imaging, so I bought a Gerd Neumann Aurora Flat Panel.

The first problem when it comes to flat frames and the Atik 383L+ is just what is the exposure length I need to get above to overcome any smearing from the mechanical shutter? I’ve heard 0.5 – 1 secs as a rough guide, but it should be easy to work out and have a measurable effect on the data.

Well, here is a range of exposures through a Red filter using the Aurora. Analysed using CCD Inspector. The resting position of the shutter is obviously on the bottom right looking at the first exposure. With increasing times this gradually decreases the effect on this corner and starts to show the real vignetting in the system on everything above 2 secs, it may be possible to get away with cutting it fine somewhere between 1 and 2 secs, but for the sake of headroom, 2 secs will be my minimum exposure length.

Scope: Borg 101EDII (@ F5.3)
Filter: Baader 1.25″ Red CCD

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