From 40e5a5811c6ffce9b0974e93cdd927cbcf60c157 Mon Sep 17 00:00:00 2001 From: Joe Hunkeler Date: Tue, 11 Aug 2015 16:51:37 -0400 Subject: Repatch (from linux) of OSX IRAF --- math/slalib/doc/prec.hlp | 53 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) create mode 100644 math/slalib/doc/prec.hlp (limited to 'math/slalib/doc/prec.hlp') diff --git a/math/slalib/doc/prec.hlp b/math/slalib/doc/prec.hlp new file mode 100644 index 00000000..4b12d918 --- /dev/null +++ b/math/slalib/doc/prec.hlp @@ -0,0 +1,53 @@ +.help prec Jun99 "Slalib Package" +.nf + + SUBROUTINE slPREC (EP0, EP1, RMATP) + + - - - - - + P R E C + - - - - - + + Form the matrix of precession between two epochs (IAU 1976, FK5) + (double precision) + + Given: + EP0 dp beginning epoch + EP1 dp ending epoch + + Returned: + RMATP dp(3,3) precession matrix + + Notes: + + 1) The epochs are TDB (loosely ET) Julian epochs. + + 2) The matrix is in the sense V(EP1) = RMATP * V(EP0) + + 3) Though the matrix method itself is rigorous, the precession + angles are expressed through canonical polynomials which are + valid only for a limited time span. There are also known + errors in the IAU precession rate. The absolute accuracy + of the present formulation is better than 0.1 arcsec from + 1960AD to 2040AD, better than 1 arcsec from 1640AD to 2360AD, + and remains below 3 arcsec for the whole of the period + 500BC to 3000AD. The errors exceed 10 arcsec outside the + range 1200BC to 3900AD, exceed 100 arcsec outside 4200BC to + 5600AD and exceed 1000 arcsec outside 6800BC to 8200AD. + The SLALIB routine slPREL implements a more elaborate + model which is suitable for problems spanning several + thousand years. + + References: + Lieske,J.H., 1979. Astron.Astrophys.,73,282. + equations (6) & (7), p283. + Kaplan,G.H., 1981. USNO circular no. 163, pA2. + + Called: slDEUL + + P.T.Wallace Starlink 23 August 1996 + + Copyright (C) 1996 Rutherford Appleton Laboratory + Copyright (C) 1995 Association of Universities for Research in Astronomy Inc. + +.fi +.endhelp -- cgit