Quote:
Originally Posted by Atmos
For astrometric purposes 1,000,000 e- is recommended but if all you’re wanting to do is remove vignetting and dust motes then it isn’t that important  |
1Me- is certainly overkill for pretty pictures but noise from a poor quality master flat will end up in your image during calibration so I reckon it's definitely worth aiming for 100K or more.
Quote:
Originally Posted by Peter Ward
The math on the flats is the same for your lights...so you need 250 odd subs for a decent S/N eh?
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It's better and worse than that, Peter. It's better because 250K or more electrons sets a fairly high bar for SNR - deliberately so because we don't want flat calibration to add much noise. It's worse because lights usually have data values much less than half full well in areas of interest. It is certainly true that you need to take lots of (short) subs with a CMOS camera at high gain.