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Source selection

Once a catalog has been defined, a source within this list can be selected using the SOURCE name command. The /ALTERNATE option will direct the search to the alternate catalog.

The source coordinates are reduced to current epoch (as defined by the last TIME command), and converted to horizontal coordinates azimuth and elevation relative to the observatory (as defined by the last OBSERVATORY command). Precession, nutation, aberration are taken into account. The motion of the Earth uses the ephemerides from the Bureau des Longitudes (BDL82). The source horizontal coordinates are printed on the screen, together with the line-of-sight components of the velocities of:

All velocities are in km/s, counted positively for outwards motions. After running the SOURCE command, a number of SIC gloabal variables are updated and contain the source right ascension (variable RA), declination (DEC), azimuth (AZIMUTH) or elevation (ELEVATION). These are global ASTRO variables, used or mnodified by other commands. In addition, a structure called astro%source% is created, and contains all output values of the SOURCE command.

SOURCE with no arguments will compute positions of all sources from the current (or alternate) catalog in a row. The SIC variables will contain the position of the last source.

SOURCE /RESET will reset all source related parameters in ASTRO and remove the ASTRO%SOURCE structure.


next up previous contents
Next: Solar system bodies Up: Computing source positions Previous: Source catalogs   Contents
Gildas manager 2018-02-21