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/node77.html | 117 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 117 insertions(+) create mode 100644 src/slalib/sun67.htx/node77.html (limited to 'src/slalib/sun67.htx/node77.html') diff --git a/src/slalib/sun67.htx/node77.html b/src/slalib/sun67.htx/node77.html new file mode 100644 index 0000000..522e009 --- /dev/null +++ b/src/slalib/sun67.htx/node77.html @@ -0,0 +1,117 @@ + + + + +SLA_DTP2V - Tangent Plane to Direction Cosines + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_DTPS2C - Plate centre from and +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_DTP2S - Tangent Plane to Spherical +

+

+

SLA_DTP2V - Tangent Plane to Direction Cosines +   +

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

CALL: +
CALL sla_DTP2V (XI, ETA, V0, V) +

+

+
GIVEN: +
+
+ + + + + + + + + +
XI,ETADtangent plane coordinates of star (radians)
V0D(3)direction cosines of tangent point
+

+
RETURNED: +
+
+ + + + + +
VD(3)direction cosines of star
+

+
NOTES: +
+
1. +
If vector V0 is not of unit length, the returned vector V will +be wrong. +
2. +
If vector V0 points at a pole, the returned vector V 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_DTP2S. +
+
+ +next + +up + +previous +
+ Next: SLA_DTPS2C - Plate centre from and +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_DTP2S - Tangent Plane to Spherical +

+

+

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