Help! Image type changes mid-DP!

Posted by Jeffrey Larsen on
URL: http://astroimagej.170.s1.nabble.com/Help-Image-type-changes-mid-DP-tp293.html

Hi!

We were just getting started with AstroImageJ with some data in 16 bit unsigned int and tried to use the DP to do our bias and flat corrections.  After sorting the data the right way, we get a strange behavior.

Our bias images have means in the ~200 ADU range.
The master bias output by DP has a mean in the 33000 range (actually 200'ish + half of 65538).
The reduction is ruined because that large pedestal takes otherwise proper flats and distorts them badly.

Here is the strange part though....
1.  Start AstroImageJ fresh.  Load one of our images and examine it.  Values in the ~200 ADU range.
2.  Run DP.  Things get ruined due to the previous problem.  Processed images popped up with values in the -23000's.
3. Take that same image window that popped up, open the same image I did in step 1.  Values now appear in the 33000 range for this image.
4.  Quit and restart aij and then load the same image again.  Values back in the ~200 ADU range again.

This happens for both a Windows 64 bit and Linux 64 bit install.  Somehow there seems to be a signed/unsigned thang happening!

Help?