Reduction Information
Processing Images
When the image is read out, you can immediately display it; you'll see
a gap in the display because you are reading out of both amps. To make
a joined, trimmed up image, you'll want to do the following (in iraf, of course):
- chpixtype image.fits image.fits type=ushort (may not be necessary)
- mkmsc image.fits image.fits descrip=2amp.dat
- ccdproc image.fits overscan+ trim+ merge+ biassec=!biassec trimsec=!trimsec
Note that the 2amp.dat example file is for 2200x4200 images (the default),
and you may want to alter as you see fit.
Zeropoint
Zeropoints will change, of course, but here's the zeropoint solution for
the M filter from Spring 2004, using an instrumental magnitude zeropoint
of 25:
m = 25 - 3.665 - 0.153*(secz) - 0.181*(B-V)
So 1 count per second is a magnitude of 25 - 3.665 - 0.153*1.0 - 0.181*1.0
= 21.001 (assuming unit airmass and a B-V color of 1.0).
So for a 900 sec exposures, and a pixel scale of 1.45 "/pix, this is equivalent
to a surface brightness of
mu = 21.001 + 2.5log(900) + 2.5log(1.45*1.45)
= 29.2 mag/asec2
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Last Updated: 18/4/04