WCI_CNS2S

Convert a coordinate pair from one system to another

Invocation

CALL WCI_CNS2S( SYSIN, POSIN, SYSOUT, POSOUT, STATUS )

Description

Converts a celestial position in one coordinate system to the same sky point in a second system. This is performed by converting to the FK5 system in the epoch defined by the input, precessing this position to the output epoch and converting to the output system.

Arguments

• SYSIN = INTEGER (given)
  The coordinate system of the supplied position
• POSIN[2] = DOUBLE (given)
  The supplied position, in coordinate system specified by SYSIN
• SYSOUT = INTEGER (given)
  The coordinate system of the required position
• POSOUT[2] = DOUBLE (returned)
  The input position converted to the system specified by SYSOUT
• STATUS = INTEGER (given and returned)
  The global status.

Accuracy

The test procedure tst_wci_cns2s applying 2 WCI_CNS2S operations to shift from FK4 -> FK5 and back to FK4, with different equinoxes and epochs, averaged over the whole celestial sphere, recovers the original position to an average accuracy of 0.00108 arcsec, with a worst case of 0.00132 arcsec.

References

• WCI Subroutine Guide