PixInsight Flat Problem

[William McLaughlin]

For some reason, PI seems to not flat correct properly during calibration. I had not tried PI for calibration (dark subtract and flat field), having use CCD Stack for that to date. Using the same master files for dark and flat (both calibration frames are already dark and bias subtracted so those options are left unchecked) in PI (left) and CCDStack (right) I get what you see.  Corner was originally darker from vignetting so it looks to be over corrected. Any ideas?

[Juan Conejero]

Hi,

Have you created the master bias, dark and flat frames with PixInsight? Have you followed our master frame creation tutorial?

[William McLaughlin]

No, these were created in CCDStack since that is what I have used until now.

It seems odd that the master dark created in CCDStack works in PI, but not the master flat.

I suppose I can go back and reprocess the component support frames in PI.

[Juan Conejero]

No, these were created in CCDStack

Then this explains the problem. Unfortunately, with a few exceptions, raw data are incompatible between applications. A cause is that the FITS and TIFF formats don't define a number of critical image elements, such as the range of pixel values for floating point data, the meaning of signed integer data, black and white points, color spaces, etc. This causes many problems. Other reasons are related to the fact that some applications 'protect' themselves by making migration of data more difficult than what is strictly necessary.

If you generate your masters with PixInsight there shouldn't be any problems. I recommend you follow Vicent's tutorial. Let us know how it goes.

[William McLaughlin]

OK, tried that and it works nicely. In fact, for some reason it handles partial hot columns better than CCDStack.

Thanks!

BTW, I noted that for some reason, even if I have just saved a process icon, when I go to close PixInsight it warns me that I have NOT saved the process icon. Minor issue, to be sure, but worth noting.