ASTRO comes with a short precedure named astro-site.astro, located in the pro directory of your GILDAS installation. This file is executed at the beginning of each ASTRO session, and is used to set default values for the time and observatory parameters.
!
! Observatory and time initialization
!
astro\set dut1 -0.3 ! November 2007 Bulletin D 98 of IERS
astro\set dtdt 65.184 ! January 2006 Bulletin C 30 of IERS
!
astro\observatory ! Select default observatory
astro\time ! Use current system time
!
if (observatory.eq."BURE") then
astro\set azimuth south
astro\catalog gag_data:phase-pdb
sic\message i site "Plateau de Bure defaults selected"
else if (observatory.eq."PICOVELETA") then
astro\set azimuth north
sic\message i site "Pico Veleta defaults selected"
else
sic\message i site "No known defaults for this observatory"
endif
Note the SET AZIMUTH NORTH|SOUTH command, which is used to define the azimuth to be zero in the North or South directions, to conform to local conventions.