Efficiency considerations

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/node215.html | 87 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 87 insertions(+) create mode 100644 src/slalib/sun67.htx/node215.html (limited to 'src/slalib/sun67.htx/node215.html') diff --git a/src/slalib/sun67.htx/node215.html b/src/slalib/sun67.htx/node215.html new file mode 100644 index 0000000..020487b --- /dev/null +++ b/src/slalib/sun67.htx/node215.html @@ -0,0 +1,87 @@ + + + + +Efficiency considerations + + + + + + + + + + + +

+ +

+
+ Next: The Hipparcos Catalogue and the ICRS +
+Up: Apparent Place to Observed Place +
+ Previous: Refraction +

+Efficiency considerations +

+The complete apparent place to observed place transformation +can be carried out by calling +sla_AOP. +For improved efficiency +in cases of more than one star or a sequence of times, the +target-independent calculations can be done once by +calling +sla_AOPPA, +the time can be updated by calling +sla_AOPPAT, +and +sla_AOPQK +can then be used to perform the +apparent-to-observed transformation. The reverse transformation +is available through +sla_OAP +and +sla_OAPQK. +(n.b. These routines use accurate but computationally-expensive +refraction algorithms for zenith distances beyond about $76^\circ$ .For many purposes, in-line code tailored to the accuracy requirements +of the application will be preferable, for example ignoring UT1-UTC, +omitting diurnal aberration and using +sla_REFZ +to apply the refraction.) +

+ +

+
+ Next: The Hipparcos Catalogue and the ICRS +
+Up: Apparent Place to Observed Place +
+ Previous: Refraction +

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

+ + -- cgit