Re: Three questions about Aperture Photometry Settings screen

Posted by karenacollins on May 19, 2022; 12:29am
URL: http://astroimagej.170.s1.nabble.com/Three-questions-about-Aperture-Photometry-Settings-screen-tp1911p1913.html

The ADU values AIJ has access to are the output from the ADU on your chip, which is likely limited to 16 bits, or about 65000 ADU. This makes sense for your camera spec since the CCD well depth is 88391 electrons and dividing by your detector gain of 1.37 is about 65K. So, you should probably set your saturation value to something like 60,000. The linearity  setting is more hand-wavy, but for most modern CCDs a value of ~40,000 seems reasonable.

Please note that these values are affected by calibration too, so you may have to adjustment them down if you have particularly high sky bias or background that is being subtracted, or if your flat division changes the values dramatically.

Finally, keep in mind that these settings do not affect the light curve results in any way. They are only intended to give you a guide in the ref star panel that a star might be getting close to concerning limits.

Karen