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/node138.html | 116 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 src/slalib/sun67.htx/node138.html (limited to 'src/slalib/sun67.htx/node138.html') diff --git a/src/slalib/sun67.htx/node138.html b/src/slalib/sun67.htx/node138.html new file mode 100644 index 0000000..d363298 --- /dev/null +++ b/src/slalib/sun67.htx/node138.html @@ -0,0 +1,116 @@ + + + + +SLA_PA - to Parallactic Angle + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_PAV - Position-Angle Between Two Directions +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_OBS - Observatory Parameters +

+

+

    +
+SLA_PA - $h,\delta$ to Parallactic Angle +

+
+
ACTION: +
Hour angle and declination to parallactic angle +(double precision). +

CALL: +
D = sla_PA (HA, DEC, PHI) +

+

+
GIVEN: +
+
+ + + + + + + + + + + + + +
HADhour angle in radians (geocentric apparent)
DECDdeclination in radians (geocentric apparent)
PHIDlatitude in radians (geodetic)
+

+
RETURNED: +
+
+ + + + + +
sla_PADparallactic angle (radians, in the range $\pm \pi$)
+

+
NOTES: +
+
1. +
The parallactic angle at a point in the sky is the position +angle of the vertical, i.e. the angle between the direction to +the pole and to the zenith. In precise applications care must + be taken only to use geocentric apparent $[\,h,\delta\,]$ and to consider + separately the effects of atmospheric refraction and telescope + mount errors. +
2. +
At the pole a zero result is returned. +
+
+ +next + +up + +previous +
+ Next: SLA_PAV - Position-Angle Between Two Directions +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_OBS - Observatory Parameters +

+

+

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