Re: Combining slices loses FITS header data

Posted by Bill Tschumy on Sep 15, 2022; 4:00pm
URL: http://astroimagej.170.s1.nabble.com/Combining-slices-loses-FITS-header-data-tp1997p2001.html

Actually here is a better comparison.  This is the header from ASTAP after a calibration and alignment:

T_Cas_Light_V_10s_001_aligned.txt

Here is the header after the 10 calibrated and aligned images were stacked.

!T_Cas_V_stacked.txt

As you can see, most info is preserved.  It looks like the DATE-OBS was replaced with the average of the DATE-OBS of the subs.  The EXPTIME was replaced with the sum of the individual exposure times (not sure if that is really correct, but not critical).

He also adds:

JD-AVG  = 2.459822664406E+006         / Julian Day of the observation mid-point.
DATE-AVG= '2022-08-31T03:56:45'                                                

Looks like the WCS data is changed slightly.  Not sure if he averaged these in some way or what.  We could ask Han what he did.