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diff --git a/math/slalib/doc/fk524.hlp b/math/slalib/doc/fk524.hlp new file mode 100644 index 00000000..ed86273b --- /dev/null +++ b/math/slalib/doc/fk524.hlp @@ -0,0 +1,81 @@ +.help fk524 Jun99 "Slalib Package" +.nf + + SUBROUTINE slFK54 (R2000,D2000,DR2000,DD2000,P2000,V2000, + : R1950,D1950,DR1950,DD1950,P1950,V1950) + + - - - - - - + F K 5 4 + - - - - - - + + Convert J2000.0 FK5 star data to B1950.0 FK4 (double precision) + + This routine converts stars from the new, IAU 1976, FK5, Fricke + system, to the old, Bessel-Newcomb, FK4 system. The precepts + of Smith et al (Ref 1) are followed, using the implementation + by Yallop et al (Ref 2) of a matrix method due to Standish. + Kinoshita's development of Andoyer's post-Newcomb precession is + used. The numerical constants from Seidelmann et al (Ref 3) are + used canonically. + + Given: (all J2000.0,FK5) + R2000,D2000 dp J2000.0 RA,Dec (rad) + DR2000,DD2000 dp J2000.0 proper motions (rad/Jul.yr) + P2000 dp parallax (arcsec) + V2000 dp radial velocity (km/s, +ve = moving away) + + Returned: (all B1950.0,FK4) + R1950,D1950 dp B1950.0 RA,Dec (rad) + DR1950,DD1950 dp B1950.0 proper motions (rad/trop.yr) + P1950 dp parallax (arcsec) + V1950 dp radial velocity (km/s, +ve = moving away) + + Notes: + + 1) The proper motions in RA are dRA/dt rather than + cos(Dec)*dRA/dt, and are per year rather than per century. + + 2) Note that conversion from Julian epoch 2000.0 to Besselian + epoch 1950.0 only is provided for. Conversions involving + other epochs will require use of the appropriate precession, + proper motion, and E-terms routines before and/or after + FK524 is called. + + 3) In the FK4 catalogue the proper motions of stars within + 10 degrees of the poles do not embody the differential + E-term effect and should, strictly speaking, be handled + in a different manner from stars outside these regions. + However, given the general lack of homogeneity of the star + data available for routine astrometry, the difficulties of + handling positions that may have been determined from + astrometric fields spanning the polar and non-polar regions, + the likelihood that the differential E-terms effect was not + taken into account when allowing for proper motion in past + astrometry, and the undesirability of a discontinuity in + the algorithm, the decision has been made in this routine to + include the effect of differential E-terms on the proper + motions for all stars, whether polar or not. At epoch 2000, + and measuring on the sky rather than in terms of dRA, the + errors resulting from this simplification are less than + 1 milliarcsecond in position and 1 milliarcsecond per + century in proper motion. + + References: + + 1 Smith, C.A. et al, 1989. "The transformation of astrometric + catalog systems to the equinox J2000.0". Astron.J. 97, 265. + + 2 Yallop, B.D. et al, 1989. "Transformation of mean star places + from FK4 B1950.0 to FK5 J2000.0 using matrices in 6-space". + Astron.J. 97, 274. + + 3 Seidelmann, P.K. (ed), 1992. "Explanatory Supplement to + the Astronomical Almanac", ISBN 0-935702-68-7. + + P.T.Wallace Starlink 19 December 1993 + + Copyright (C) 1995 Rutherford Appleton Laboratory + Copyright (C) 1995 Association of Universities for Research in Astronomy Inc. + +.fi +.endhelp |