Re: Same Photometry Settings on Same Image - different results

Posted by clkotnik on Aug 08, 2019; 9:16pm
URL: http://astroimagej.170.s1.nabble.com/Same-Photometry-Settings-on-Same-Image-different-results-tp1199p1202.html

I have what I hope is a clue.  

Looking at the FITS header it seems the values of BZERO and BSCALE are uncommon values.  I wrote a little python program that read the two files in and wrote them back out.  As I understand it, the scaling factor and zero point are removed and the data are in signed floating point rather than unsigned integer in the output file.  When I perform your simple test with using the mouse to see the peak value interactively and when I perform photometry on an image sequence the problem is not present.


An updated ZIP of my example directory is here.  The rewritten files are the two with rescaled_ prepended to the name.  In addition I saved the FITS headers to text files for each image.  You can see that BITPIX, BSCALE and BZERO are the difference.

I hope this helps,
Cliff