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/node105.html | 166 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 166 insertions(+) create mode 100644 src/slalib/sun67.htx/node105.html (limited to 'src/slalib/sun67.htx/node105.html') diff --git a/src/slalib/sun67.htx/node105.html b/src/slalib/sun67.htx/node105.html new file mode 100644 index 0000000..dde5fc9 --- /dev/null +++ b/src/slalib/sun67.htx/node105.html @@ -0,0 +1,166 @@ + + + + +SLA_FK45Z - FK4 to FK5, no P.M. or Parallax + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_FK524 - FK5 to FK4 +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_FK425 - FK4 to FK5 +

+

+

SLA_FK45Z - FK4 to FK5, no P.M. or Parallax +   +

+
+
ACTION: +
Convert B1950.0 FK4 star data to J2000.0 FK5 assuming zero +proper motion in the FK5 frame. + This routine converts stars from the old, Bessel-Newcomb, FK4 + system to the new, IAU 1976, FK5, Fricke system, in such a + way that the FK5 proper motion is zero. Because such a star + has, in general, a non-zero proper motion in the FK4 system, + the routine requires the epoch at which the position in the + FK4 system was determined. The method is from appendix 2 of + reference 1, but using the constants of reference 4. +

CALL: +
CALL sla_FK45Z (R1950,D1950,BEPOCH,R2000,D2000) +

+

+
GIVEN: +
+
+ + + + + + + + + + + + + +
R1950DB1950.0 FK4 $\alpha$ at epoch BEPOCH (radians)
D1950DB1950.0 FK4 $\delta$ at epoch BEPOCH (radians)
BEPOCHDBesselian epoch (e.g. 1979.3D0)
+

+
RETURNED: +
+
+ + + + + + + + + +
R2000DJ2000.0 FK5 $\alpha$ (radians)
D2000DJ2000.0 FK5 $\delta$ (radians)
+

+
NOTES: +
+
1. +
The epoch BEPOCH is strictly speaking Besselian, but +if a Julian epoch is supplied the result will be +affected only to a negligible extent. +
2. +
Conversion from Besselian epoch 1950.0 to Julian epoch + 2000.0 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 FK45Z is called. +
3. +
In the FK4 catalogue the proper motions of stars within + $10^{\circ}$ of the poles do not include the differential + E-terms 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 $\Delta\alpha$, the errors resulting from this simplification are less than + 1 milliarcsecond in position and 1 milliarcsecond per + century in proper motion. +
4. +
See also sla_FK425, sla_FK524, sla_FK54Z. +
+

+
REFERENCES: +
+
1. +
Aoki, S., et al., 1983. Astr.Astrophys., 128, 263. +
2. +
Smith, C.A. et al., 1989. Astr.J. 97, 265. +
3. +
Yallop, B.D. et al., 1989. Astr.J. 97, 274. +
4. +
Seidelmann, P.K. (ed), 1992. Explanatory + Supplement to the Astronomical Almanac, ISBN 0-935702-68-7. +
+
+ +next + +up + +previous +
+ Next: SLA_FK524 - FK5 to FK4 +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_FK425 - FK4 to FK5 +

+

+

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