Quote:
Originally Posted by Screwdriverone
Hi Ray,
Greg mentioned he uses the cursor in CCDStack to find the ADU value, although, as I use an Atik as well and am a bit of a noob still when it comes to taking flats with my light box, what do you suggest I use to determine the ADU value of the fits files? I think it works in Nebulosity when I debayer the fits file and go to the info page, but I am not confident this is correct?
Any tips on determining the correct ADU per flat would be of great help, as I find some flats (say 0.5 sec with my light box) give me a histogram in Nebulosity between say 18,000 and 30,000 so I guess that is somewhere in the 24,000 range for ADU?
Is there an easier way?
Thanks
Chris
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Hi Chris. there is no need for extreme precision. Flats in the 18,000-30,000 range should be fine if you take one for each light. I think that Nebulosity allows you to read out the ADU value under the cursor after you have taken an image, which should be fine for determining average flat exposure. The other thing that would work OK is to look at the real time histogram display (normally in the top right corner) and set the flat exposure so that the main peak is about the centre of the histogram.
From memory, your Atik has a Sony chip, so bear in mind that you might be able to get by without flats for short to medium exposures if your sky is OK. Suggest that you try processing one of your image sequences with and without flats to see if they are worth the effort for your system and the imaging you do - although of course, you will need flats if you must correct vignetting or donuts. Regards Ray
regards ray