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.help pcd Jun99 "Slalib Package"
.nf
SUBROUTINE slPCD (DISCO,X,Y)
- - - -
P C D
- - - -
Apply pincushion/barrel distortion to a tangent-plane [x,y].
Given:
DISCO d pincushion/barrel distortion coefficient
X,Y d tangent-plane coordinates
Returned:
X,Y d distorted coordinates
Notes:
1) The distortion is of the form RP = R*(1 + C*R**2), where R is
the radial distance from the tangent point, C is the DISCO
argument, and RP is the radial distance in the presence of
the distortion.
2) For pincushion distortion, C is +ve; for barrel distortion,
C is -ve.
3) For X,Y in units of one projection radius (in the case of
a photographic plate, the focal length), the following
DISCO values apply:
Geometry DISCO
astrograph 0.0
Schmidt -0.3333
AAT PF doublet +147.069
AAT PF triplet +178.585
AAT f/8 +21.20
JKT f/8 +13.32
4) There is a companion routine, slUPCD, which performs
an approximately inverse operation.
P.T.Wallace Starlink 31 December 1992
Copyright (C) 1995 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
.fi
.endhelp
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