diff options
Diffstat (limited to 'noao/astcat/src/awcs/treqst.x')
| -rw-r--r-- | noao/astcat/src/awcs/treqst.x | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/noao/astcat/src/awcs/treqst.x b/noao/astcat/src/awcs/treqst.x new file mode 100644 index 00000000..c4cd27e5 --- /dev/null +++ b/noao/astcat/src/awcs/treqst.x @@ -0,0 +1,49 @@ +# This routine was copied from the stsdas$pkg/analysis/gasp/gasplib/ +# directory. See stsdas$copyright.stsdas for copyright restrictions. +# + +define ARCSEC_PER_RADIAN 206264.8062470964d0 + +# TREQST -- Procedure to convert RA and Dec to standard coordinates +# given the plate centre. + +procedure treqst (plate_centre_ra, plate_centre_dec, object_ra, object_dec, + xi_object, eta_object) + +double plate_centre_ra #I plate ra center (radians) +double plate_centre_dec #I plate dec center (radians) +double object_ra #I object ra center (radians) +double object_dec #I object dec center (radians) +double xi_object #O object xi standard coordinate (arcsecs) +double eta_object #O object eta standard coordinate (arcsecs) + +#double div +double ra, cosra, sinra, cosdec, sindec, cosd0, sind0, cosdist + +begin + ra = object_ra - plate_centre_ra + cosra = cos (ra) + sinra = sin (ra) + cosdec = cos (object_dec) + sindec = sin (object_dec) + cosd0 = cos (plate_centre_dec) + sind0 = sin (plate_centre_dec) + cosdist = sindec * sind0 + cosdec * cosd0 * cosra + xi_object = cosdec * sinra * ARCSEC_PER_RADIAN / cosdist + eta_object = (sindec * cosd0 - cosdec * sind0 * cosra) * + ARCSEC_PER_RADIAN / cosdist + +# # Find the divisor. +# div = (sin(object_dec) * sin(plate_centre_dec) + +# cos(object_dec) * cos(plate_centre_dec) * +# cos(object_ra -plate_centre_ra)) +# +# # Compute standard coords and convert to arcsec +# xi_object = cos(object_dec) * sin(object_ra-plate_centre_ra) * +# ARCSEC_PER_RADIAN/div +# eta_object = (sin(object_dec) * cos(plate_centre_dec) - +# cos(object_dec) * dsin(plate_centre_dec) * +# cos(object_ra - plate_centre_ra)) * +# ARCSEC_PER_RADIAN/div + +end |