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include <imhdr.h>
include "quadgeom.h"
define OPT_REFLECT 4
# GAINMEASURE -- Calculate the gain (e/ADU) and RON of a CCD using the CTIO
# (Bruce Attwood) algorithm.
# Input are a pair of high signal level exposures (Flat1, Flat2) and a pair of
# zero exposures (Zero1, Zero2). We then calculate:
#
# epadu = <Flat1> + <Flat2> - (<Zero1> + <Zero2>) / var{Diff_F} - Var{Diff_Z}
# RON = RMS {Diff_Z} * epadu / sqrt(2)
#
# Where:
#
# diff_Z = Zero1 - Zero2
# diff_F = Flat1 - Flat2
#
# The statistics must be calculated for regions free of bad pixels and other
# defects, and with reasonably uniform illumination.
procedure t_gainmeasure ()
pointer flat1, flat2 #TI High level images
pointer zero1, zero2 #TI Zero level images
char section[SZ_LINE] #TI Section for calculation
char buffer[SZ_LINE]
int npix, x1, x2, y1, y2, amp
pointer sp, f1, f2, z1, z2, fd, zd, qg
real f1bar, f2bar, z1bar, z2bar, fdbar, zdbar
real f1sigma, f2sigma, z1sigma, z2sigma, fdsigma, zdsigma
real div, epadu, ron
bool headers
pointer immap(), imgs2r()
bool clgetb(), quadsect()
int hdmaccf()
begin
# Open instrument file
call clgstr ("instrument", buffer, SZ_FNAME)
call hdmopen (buffer)
# Map input images
call clgstr ("flat1", buffer, SZ_LINE)
flat1 = immap (buffer, READ_ONLY, 0)
call clgstr ("flat2", buffer, SZ_LINE)
flat2 = immap (buffer, READ_ONLY, 0)
call clgstr ("zero1", buffer, SZ_LINE)
zero1 = immap (buffer, READ_ONLY, 0)
call clgstr ("zero2", buffer, SZ_LINE)
zero2 = immap (buffer, READ_ONLY, 0)
# Get section over which measurement is to be made.
call clgstr ("section", section, SZ_LINE)
# See if headers are to be printed
headers = clgetb ("print_headers")
# Set-up quadgeom structure. We blithely assume all images are the same.
call quadalloc (qg)
if (hdmaccf (flat1, "HDR_REV") == NO) {
call quadgeom (flat1, qg, "", "")
} else {
call qghdr2 (flat1, qg)
}
# call quaddump (qg)
if (headers) {
call printf ("#")
do amp = 1, QG_NAMPS (qg) {
call printf ("%9wAmp%2s%5w")
call pargstr (Memc[QG_AMPID (qg, amp)])
}
call printf ("\n")
call printf ("#")
do amp = 1, QG_NAMPS (qg) {
call printf ("%5wGain%4wRON%3w")
}
call printf ("\n")
call printf ("#")
do amp = 1, QG_NAMPS (qg) {
call printf ("%3w(e-/ADU)%2w(e-)%2w")
}
call printf ("\n")
}
call printf ("%1w")
do amp = 1, QG_NAMPS (qg) {
if (quadsect (qg, section, OPT_REFLECT, amp, x1, x2, y1, y2)) {
npix = (abs(y2 - y1) + 1) * (abs(x2 - x1) + 1)
# Allocate working arrays
call smark (sp)
call salloc (fd, npix, TY_REAL)
call salloc (zd, npix, TY_REAL)
# Read data
f1 = imgs2r (flat1, x1, x2, y1, y2)
f2 = imgs2r (flat2, x1, x2, y1, y2)
z1 = imgs2r (zero1, x1, x2, y1, y2)
z2 = imgs2r (zero2, x1, x2, y1, y2)
# Calculate differences
call asubr (Memr[f1], Memr[f2], Memr[fd], npix)
call asubr (Memr[z1], Memr[z2], Memr[zd], npix)
# Calculate means and standard deviations
call aavgr (Memr[f1], npix, f1bar, f1sigma)
call aavgr (Memr[f2], npix, f2bar, f2sigma)
call aavgr (Memr[z1], npix, z1bar, z1sigma)
call aavgr (Memr[z2], npix, z2bar, z2sigma)
call aavgr (Memr[fd], npix, fdbar, fdsigma)
call aavgr (Memr[zd], npix, zdbar, zdsigma)
# call eprintf ("f1bar=%g f1sigma=%g\n")
# call pargr (f1bar)
# call pargr (f1sigma)
# call eprintf ("f2bar=%g f2sigma=%g\n")
# call pargr (f2bar)
# call pargr (f2sigma)
# call eprintf ("z1bar=%g z1sigma=%g\n")
# call pargr (z1bar)
# call pargr (z1sigma)
# call eprintf ("z2bar=%g z2sigma=%g\n")
# call pargr (z2bar)
# call pargr (z2sigma)
# call eprintf ("fdbar=%g fdsigma=%g\n")
# call pargr (fdbar)
# call pargr (fdsigma)
# call eprintf ("zdbar=%g zdsigma=%g\n")
# call pargr (zdbar)
# call pargr (zdsigma)
div = fdsigma**2 - zdsigma**2
if (div > 0.0) {
epadu = ((f1bar + f2bar) - (z1bar + z2bar)) / div
ron = epadu * zdsigma / 1.41421356
} else {
epadu = INDEF
ron = INDEF
}
# Print results
call printf ("%3w%6.2f%2w%6.2f%2w")
call pargr (epadu)
call pargr (ron)
# Free working arrays
call sfree (sp)
}
}
call printf ("\n")
# Tidy up
call imunmap (flat1)
call imunmap (flat2)
call imunmap (zero1)
call imunmap (zero2)
end
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