IRA_ISCS

Return a list of supported sky coordinate systems

Description:

A string is returned containing a list of names identifying the supported sky coordinate systems. The names in the output list are separated by commas.

By default, Equatorial and Ecliptic coordinates are referred to the mean equinox of Besselian epoch 1950.0. The calling application can override this default by appending a string known as an " equinox specifier" to the end of the SCS name (in fact all IRA routines will accept any unambiguous abbreviation of the SCS name). An equinox specifier consists of a year with upto 4 decimal places, preceded with the letter B or J to indicate a Besselian or Julian epoch, and enclosed in parentheses. The named coordinate system is then referred to the mean equinox of the epoch given in the equinox specifier. The following are examples of legal SCS values; EQUATORIAL(B1950), EQUAT(J2000), ECLIP, ECLIP(1983.2534), etc. If the date is not preceded with either B or J (as in the last example), a Besselian epoch is assumed if the date is less than 1984.0, and a Julian epoch is assumed otherwise.

The currently supported sky coordinate systems are:

EQUATORIAL

The longitude axis is Right Ascension, the latitude axis is Declination. Other legal names can be made by appending an equinox specifier (eg EQUATORIAL(B1983.5) ). If no equinox specifier is added, the coordinates are referred to the mean equinox of Besselian epoch 1950.0. If the equinox is described by a Besselian epoch, the old FK4 Bessel-Newcomb system is used. If a Julian epoch is used, the new IAU 1976, FK5, Fricke system is used.

GALACTIC

The longitude axis is galactic longitude and the latitude axis is galactic latitude, given in the IAU 1958 galactic coordinate system.

ECLIPTIC

The longitude axis is ecliptic longitude and the latitude axis is ecliptic latitude. Other legal names can be made by appending an equinox specifier (eg ECLIPTIC(B1983.5) ). If no equinox specifier is added, the coordinates are referred to the mean equinox of Besselian epoch 1950.0.

AZEL

The longitude axis is horizon azimuth and the latitude axis is horizon elevation.

All sky coordinate values supplied to, or returned from any IRA routine, are given in units of radians.

Invocation

CALL IRA_ISCS( LIST, STATUS )

Arguments

LIST = CHARACTER ∗ ( ∗ ) (Returned)
The list of supported sky coordinate system names. The character variable supplied for this argument should have a declared size equal to the value of parameter IRA__SZCLS. If the supplied string is not long enough to hold all the names, a warning message is given, but no error status is returned.
STATUS = INTEGER (Given and Returned)
The global status.