From d54fe7c1f704a63824c5bfa0ece65245572e9b27 Mon Sep 17 00:00:00 2001 From: Joseph Hunkeler Date: Wed, 4 Mar 2015 21:21:30 -0500 Subject: Initial commit --- src/slalib/sun67.htx/node190.html | 137 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 137 insertions(+) create mode 100644 src/slalib/sun67.htx/node190.html (limited to 'src/slalib/sun67.htx/node190.html') diff --git a/src/slalib/sun67.htx/node190.html b/src/slalib/sun67.htx/node190.html new file mode 100644 index 0000000..09def53 --- /dev/null +++ b/src/slalib/sun67.htx/node190.html @@ -0,0 +1,137 @@ + + + + +SLA_V2TP - Direction Cosines to Tangent Plane + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_VDV - Scalar Product +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_UNPCD - Remove Radial Distortion +

+

+

SLA_V2TP - Direction Cosines to Tangent Plane +   +

+
+
ACTION: +
Given the direction cosines of a star and of the tangent point, +determine the star's tangent-plane coordinates + (single precision). +

CALL: +
CALL sla_V2TP (V, V0, XI, ETA, J) +

+

+
GIVEN: +
+
+ + + + + + + + + +
VR(3)direction cosines of star
V0R(3)direction cosines of tangent point
+

+
RETURNED: +
+
+ + + + + + + + + + + + + + + + + + + + + + + + + +
XI,ETARtangent plane coordinates (radians)
JIstatus:
0 = OK, star on tangent plane
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 $\alpha=0$ at the tangent point. +
3. +
The projection is called the gnomonic projection; the + Cartesian coordinates $[\,\xi,\eta\,]$ are called + standard coordinates. The latter + are in units of the distance from the tangent plane to the projection + point, i.e. radians near the origin. +
4. +
This routine is the Cartesian equivalent of the routine sla_S2TP. +
+
+ +next + +up + +previous +
+ Next: SLA_VDV - Scalar Product +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_UNPCD - Remove Radial Distortion +

+

+

+SLALIB --- Positional Astronomy Library
Starlink User Note 67
P. T. Wallace
12 October 1999
E-mail:ptw@star.rl.ac.uk +
+ + -- cgit