Re: Negative values on the histogram - what do they mean?

Posted by magnusl on Jan 05, 2022; 8:44am
URL: http://astroimagej.170.s1.nabble.com/Negative-values-on-the-histogram-what-do-they-mean-tp1713p1721.html

Hi!

Thanks.

OK, then there is something wrong with my process - fully within AIJ.

I have master bias, produced by the DP module, median checked.

I have master dark, produced by the DP module. deBias checked when producing the Master. Should it then be deselected when reusing the master Dark? I don't see much difference.

I have flats, also produced by the DP module. Median checked and Remove Gradient.

And with these settings and files, I get -7.739 for some images right now.

The Bias I use has a mean value of 370, and the dark varies between 3.5 and 191,7, if I read correctly.

The flat, when opened in AIJ, gives me values between 0.8510 (min) and 1.4992 (max). Which feels odd. When measuring in PixInsight I get a minimum of 221 and a maximum of 56983 (16-bits), with a mean of 15064.


What am I doing wrong here? And how come the values for the flat is so strange - or are they not? I'd be happy to share the files with you in a Dropbox folder?

Best,

Magnus