Quote:
Originally Posted by cventer
Interesting thread
I thought for flats you were supposed to expose histogram in half to 2/3 of full well ? So with full well of 65k I was aiming for median of around 40k. Sounds like this is too bright as well ?
What adu shoudl i aim for with 65k well depth ?
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I think it depends on the CCD. for a non ABG CCD 2/3 max is usually still in the linear part of the ccd so is ok. I'm not sure about the modern ABG CCDs.
I think that the over correction that the original poster notes is a combination of problems. It is very hard to make perfect flats. T shirt flats are good but can still be inaccurate if angled ambient light falls on the shirt.
Dome flats probably mimic the sky the best providing you can very evenly illuminate the target.
Twighlight flats are also very good but a pest to make.
I use dome flats and find they are good most of the time. They do seem to fail a bit if I image at full moon resulting in uneven correction.