This is a flow chart for dsimulator.
Some notes about it.
The input/output in light blue is in the sky plane. The input/output in green is the mask plane.
Iraf procedures are in CAPITAL letters.
The only use of actual distorsions is in LEN_SLITS. This procedure, which is triggered if ADJ_SLIT = YES, only affects the slit edges.
# Open X-Projection mapping
fdx = open (XPROJ_MAP, READ_ONLY, TEXT_FILE)
call gs_ingest (fdx, asfx, asfy)
......
# We will need to recalculate something ...
xlow = X2(sdat,ndx1) + SLIT_GAP(indat)
xupp = X1(sdat,ndx2) - SLIT_GAP(indat)
xcen = 0.5 * (xlow + xupp)
yas = Y2(sdat,ndx1)
dxlow = gseval (asfx, xcen, yas)
yas = Y1(sdat,ndx2)
dxupp = gseval (asfx, xcen, yas)
dxavg = 0.5 * (dxupp + dxlow)
dxlow = dxlow - dxavg
dxupp = dxupp - dxavg
call eprintf ("%6.3f %6.3f\n")
call pargr (dxlow)
call pargr (dxupp)
if (pc1 == CODE_AS) {
del1 = 0.
del2 = X1(sdat,ndx2) - xlow - (dxupp - dxlow)
} else if (pc2 == CODE_AS) {
del1 = xupp - X2(sdat,ndx1) + (dxlow - dxupp)
del2 = 0.
} else {
del1 = xcen - 0.5*SLIT_GAP(indat) - X2(sdat,ndx1) + dxlow
del2 = X1(sdat,ndx2) - (xcen + 0.5*SLIT_GAP(indat)) - dxupp
}
X2(sdat,ndx1) = X2(sdat,ndx1) + del1
if (del1 != 0. && RELPA(sdat,ndx1) != INDEF) {
tana = tan (RELPA(sdat,ndx1))
Y2(sdat,ndx1) = Y2(sdat,ndx1) + del1 * FLIP * tana
}
X1(sdat,ndx2) = X1(sdat,ndx2) - del2
if (del2 != 0. && RELPA(sdat,ndx2) != INDEF) {
tana = tan (RELPA(sdat,ndx2))
Y1(sdat,ndx2) = Y1(sdat,ndx2) - del2 * FLIP * tana
}
The other distorsion (based on an optical model of Keck) is done at GNOM_TO_DPROJ procedure.
#
# GNOM_TO_DPROJ: adjust gnomonic coords to curved surface, take projection
# onto plane, and apply distortion correction, resulting in distortion-
# adjusted projected coords ready for a vertical projection to slitmask.
# Double inputs, outputs; outputs may be the same arguments as inputs.
#
#####
## NB: We assume Sutin's ray trace is already producing radii to curved surface.
####
procedure gnom_to_dproj (xg, yg, xd, yd)
double xg, yg # x,y gnomonic projection
double xd, yd # returned x,y projected on plane (distorted)
double rho # radius of input angle (approx from h)
double cosa, sina # cos, sin of azimuth in image plane
begin
rho= sqrt (xg * xg + yg * yg)
cosa = yg / rho
sina = xg / rho
# Apply map gnomonic projection --> real telescope
rho = rho * (1. + DIST_C0 + DIST_C2 * rho * rho)
xd = rho * sina
yd = rho * cosa
end
In this procedure, DIST_C0 = 0.0e-4 and DIST_C2 = -1.111311e-8