SLA_AMP - Apparent to Mean

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/node18.html | 135 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 135 insertions(+) create mode 100644 src/slalib/sun67.htx/node18.html (limited to 'src/slalib/sun67.htx/node18.html') diff --git a/src/slalib/sun67.htx/node18.html b/src/slalib/sun67.htx/node18.html new file mode 100644 index 0000000..e3aee75 --- /dev/null +++ b/src/slalib/sun67.htx/node18.html @@ -0,0 +1,135 @@ + + + + +SLA_AMP - Apparent to Mean + + + + + + + + + + + + +

+ +

+
+ Next: SLA_AMPQK - Quick Apparent to Mean +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_ALTAZ - Velocities etc. for Altazimuth Mount +

SLA_AMP - Apparent to Mean + +

ACTION: +: Convert star $[\,\alpha,\delta\,]$ from geocentric apparent to +mean place (post IAU 1976). +
CALL: +: CALL sla_AMP (RA, DA, DATE, EQ, RM, DM) +

GIVEN: +

+
+ + + + + + + + + + + + + +

RA,DA	D	apparent $[\,\alpha,\delta\,]$ (radians)
DATE	D	TDB for apparent place (JD-2400000.5)
EQ	D	equinox: Julian epoch of mean place

RETURNED: +

+
+ + + + + +

RM,DM	D	mean $[\,\alpha,\delta\,]$ (radians)

NOTES: +

1. +: The distinction between the required TDB and TT is +always negligible. Moreover, for all but the most +critical applications UTC is adequate. +
2. +: The accuracy is limited by the routine sla_EVP, called + by sla_MAPPA, which computes the Earth position and + velocity using the methods of Stumpff. The maximum + error is about 0.3 milliarcsecond. +
3. +: Iterative techniques are used for the aberration and + light deflection corrections so that the routines + sla_AMP (or sla_AMPQK) and sla_MAP (or sla_MAPQK) are + accurate inverses; even at the edge of the Sun's disc + the discrepancy is only about 1 nanoarcsecond. +
4. +: Where multiple apparent places are to be converted to + mean places, for a fixed date and equinox, it is more + efficient to use the sla_MAPPA routine to compute the + required parameters once, followed by one call to + sla_AMPQK per star. +

REFERENCES: +

1. +: 1984 Astronomical Almanac, pp B39-B41. +
2. +: Lederle & Schwan, 1984. Astr.Astrophys. 134, 1-6. +

+ +

+
+ Next: SLA_AMPQK - Quick Apparent to Mean +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_ALTAZ - Velocities etc. for Altazimuth Mount +

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

+ + -- cgit