A extremely convenient mean of planning observations is to produce a diagram in which time is used as x-coordinate, and in which an horizontal bar is drawn for each selected source to indicate the time period during which the source is up. Such a plot is produced using the command HORIZON. One may use all sources in the current catalog (HORIZON /SOURCE), all planets (HORIZON /PLANET), or both. Specific objects may be called by their names using HORIZON /SOURCE name1 name2 ... or HORIZON /PLANET name1 name2 .... A source that is presently in the sun avoidance circle is written within brackets () and in italics (e.g. [NGC 2264]). When a quite long catalog is used, the command HORIZON /SOURCE NEXT n can be used repetitively to obtain plots with only n objects at a time.
Example - The following commands will plot the observability hours for the sources of the sample.sou catalog on April 1st 2008, together with planet Neptun. The output is presented in Fig. .
CATALOG GAG_DEMO:SAMPLE.SOU ! define the catalog OBSERVATORY PICOVELETA ! ... the observatory TIME 12:00 01-APR-2008 ! ... and the time HORIZON /SOURCE /PLANET NEPTUN ! produce the plot