Odd issue with master bias and dark frames

Posted by Michael Collins on May 31, 2021; 4:51pm
URL: http://astroimagej.170.s1.nabble.com/Odd-issue-with-master-bias-and-dark-frames-tp1579.html

  While doing some engineering work over the weekend, I captured sets of bias and dark frames intended to calibrate my on-sky images. I've done this before using other cameras and capture software, so the process is reasonably familiar to me. Looking at my data afterward, I encountered no difficulty nor saw any error or warning messages when the master bias and dark frames were generated. I'm unable to use the masters to calibrate the image sets, however -- they are rejected with the message: "Unable to open FITS file <path/filename>: IO error: java.io.IOException: Invalid FITS header", followed by an "open failed" dialog. The first error is also reported if I attempt to open any of the master images using File -> Open... ds9 does not report any problems with any of the masters, and inspection of the header data using imhead shows no obvious problem, though I note that BITPIX is 16 in the original FITS headers and -32 in the masters.

  A set of darks and the corresponding master are available in <https://tmckepsj.org/files/Dark_1.497.tgz>. Not sure what I'm doing wrong, but I'd be interested in learning.

  -- Mike --