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/node153.html | 120 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 src/slalib/sun67.htx/node153.html (limited to 'src/slalib/sun67.htx/node153.html') diff --git a/src/slalib/sun67.htx/node153.html b/src/slalib/sun67.htx/node153.html new file mode 100644 index 0000000..e63959a --- /dev/null +++ b/src/slalib/sun67.htx/node153.html @@ -0,0 +1,120 @@ + + + + +SLA_PRECES - Precession + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_PRECL - Precession Matrix (latest) +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_PREC - Precession Matrix (FK5) +

+

+

SLA_PRECES - Precession +   +

+
+
ACTION: +
Precession - either the old ``FK4'' (Bessel-Newcomb, pre IAU 1976) +or new ``FK5'' (Fricke, post IAU 1976) as required. +

CALL: +
CALL sla_PRECES (SYSTEM, EP0, EP1, RA, DC) +

+

+
GIVEN: +
+
+ + + + + + + + + + + + + +
SYSTEMCprecession to be applied: `FK4' or `FK5'
EP0,EP1Dstarting and ending epoch
RA,DCD$[\,\alpha,\delta\,]$, mean equator & equinox of epoch EP0
+

+
RETURNED: +
+
+ + + + + +
RA,DCD$[\,\alpha,\delta\,]$, mean equator & equinox of epoch EP1
+

+
NOTES: +
+
1. +
Lowercase characters in SYSTEM are acceptable. +
2. +
The epochs are Besselian if SYSTEM=`FK4' and Julian if `FK5'. +For example, to precess coordinates in the old system from + equinox 1900.0 to 1950.0 the call would be: +
CALL sla_PRECES ('FK4', 1900D0, 1950D0, RA, DC) +
+
3. +
This routine will NOT correctly convert between the old and + the new systems - for example conversion from B1950 to J2000. + For these purposes see sla_FK425, sla_FK524, sla_FK45Z and + sla_FK54Z. +
4. +
If an invalid SYSTEM is supplied, values of -99D0,-99D0 are + returned for both RA and DC. +
+
+ +next + +up + +previous +
+ Next: SLA_PRECL - Precession Matrix (latest) +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_PREC - Precession Matrix (FK5) +

+

+

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