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.help dv2tp Jun99 "Slalib Package"
.nf
SUBROUTINE slDVTP (V, V0, XI, ETA, J)
- - - - - -
D V T P
- - - - - -
Given the direction cosines of a star and of the tangent point,
determine the star's tangent-plane coordinates.
(double precision)
Given:
V d(3) direction cosines of star
V0 d(3) direction cosines of tangent point
Returned:
XI,ETA d tangent plane coordinates of star
J i status: 0 = OK
1 = error, star too far from axis
2 = error, antistar on tangent plane
3 = error, antistar too far from axis
Notes:
1 If vector V0 is not of unit length, or if vector V is of zero
length, the results will be wrong.
2 If V0 points at a pole, the returned XI,ETA will be based on the
arbitrary assumption that the RA of the tangent point is zero.
3 This routine is the Cartesian equivalent of the routine slDSTP.
P.T.Wallace Starlink 27 November 1996
Copyright (C) 1996 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
.fi
.endhelp
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