precess - Precess the ra and dec columns from one equinox to another.
SYNOPSYS
preces sys eq0 eq1 < file
DESCRIPTION
Precess the ra and dec columns of an starbase data table
from an equinox in either FK4 (Bessel-Newcomb,
pre-IAU1976) or the FK5 (Fricke, post-IAU1976)
system as indicated with the sys parameter.
PARAMETERS
- sys
- The coordinate system for precession. One of "FK4|fk4|FK5|fk5".
- eq0
- The initial equinox.
- eq1
- The final equinox.
- rcol
- The column name of the ra column defaults to "ra". The
column should contain RA coordinate values in hours.
- dcol
- The column name of the dec column defaults to "dec". The
column should contain Dec coordinate values in degrees.
NOTES
The epochs are Besselian if sys='FK4' and Julian if 'FK5'.
For example, to precess coordinates in the old system from
equinox 1900.0 to 1950.0 the command would be
precess FK4 1900.0 1950.0 < targets
This routine will not correctly convert between the old and
the new systems - for example conversion from B1950 to J2000.
For these purposes see fk45 and
fk54.
SEE ALSO
- precess.src
- Source text of precess.
- slalink.1
- programs available with the slalink extensions to tawk.
- slalink.4
- functions available with the slalink extensions to tawk.
- fk45
- Convert the ra and dec columns of an starbase data table from FK4 to FK5.
- fk54
- Convert the ra and dec columns of an starbase data table from FK5 to FK4.