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Old 30-05-2020, 09:47 AM
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Saturn488 (Chrys)
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Determine light box brightness for flats

Iíve already configured SGP for taking my flats but I wanted to ask how you determine the brightness of your light box to take accurate flats?

I adjusted my brightness until it could resolve the value it needed in the flats wizard but unsure if that was the right way to do it.
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Old 31-05-2020, 08:39 AM
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The proof is in using the flat and does it correct the vignetting and any dust donuts?

I find around 18,000 ADU works for flats with various scopes and cameras.
Matched with accurate darks at the same temperature and perhaps a good bias (I don't always use a bias and always test before I calibrate a set of exposures).

I might also add the minimum exposure I go for is about 3 seconds but that is with cameras with a physical shutter. Less than that and you see artifacts from the shadow of the shutter. But for cameras with an electronic shutter like ZWO and QHY cameras this is not an issue.

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Old 31-05-2020, 08:40 PM
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The_bluester (Paul)
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Actually I would add to that. My ASI294 is a somewhat tricky one calibration wise and I aim for 10 seconds exposure flats (With a corresponding 10 second master dark flat) and I aim for about 32K ADU and I try to make the masters up out of at least 50 exposures of each type (Dark flat and flat) The ten second exposure means a very dim panel and a couple of layers of white cloth over the flat panel.

No bias frames for the 294 due to how they are driven, bias frames don't work well with them.
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