7C. Shifting the stacked images

You may notice that the stacked image in one filter will be offset by integer amounts from the stacked images in another filter. We use the WCS to determine these shifts, and imshift to then reshift them, using the philtrans.cl script:

files WLM*.fits > dstack
philtrans dstack WLMU.fits

Will shift all of the stacked images so they line up with the reference image "WLMU.fits", in this case. The way we've executed this, the new images will replace the old.

One of the wonderful, wacky things about how IRAF handles the WCS is that the bad pixel mask creating in the stacking operation are unaffected. Furthermore, we can now imcopy the sections of the shifted, stacked images to keep just the good stuff, and the bad pixel masks are STILL appropriate!