Display information about a source at the current time or a specified time.

Mandatory Arguments:

Source source

The source to describe.

Optional Arguments:

Date utc

The date and time to use when calculating the displayed statistics. When this argument is omitted the date and time at which the command is executed are used instead.

Double horizon

The elevation of the local horizon to be used when calculating the rise and set times. When this argument is omitted the value that was last set via the horizon command, is used.

Example:

The following example shows contemporary details about the moon.

  show moon

An example of the possible output is:

 Source: moon  (08-DEC-2010 22:37:55 UTC, 19:55:05 LST)
  AZ: 182:04:21.798  EL:  32:54:00.405
  RA:  19:47:41.079 DEC: -19:50:30.776
  Galactic longitude:  20:36:27.408 latitude: -20:51:34.221
  Currently above the 7 degree horizon (setting).
  Next sets in 4.3 hours at 09-DEC-2010 02:55:38 UTC, 0:13:30 LST
  and rises in 20.1 hours at 09-DEC-2010 18:43:05 UTC, 16:03:33 LST
  Distance from the sun = 38.5 degrees. Distance from the moon = 0.0 degrees.

Note that the 7 degree horizon that is shown here implies that prior to this command, eg. in the initialization file, the following command was invoked.

  horizon 7

To override this temporarily, for example to see when the sun is going to set, you could use the optional horizon argument of the show command, as follows:

  show sun, horizon=0

Similarly, to show the position and almanac of a source at a different time, one can use the optional utc argument, as in the following pair of examples.

  show moon, utc=$date+1:30:00
  ...
  show moon, utc=09-DEC-2010:00:09:38

In the first case the expression $date+1:30:00 has been used to ask for the position of the moon in 1 and a half hours from the current date and time. In the second, the position of the moon has been requested on the 9th of December 2010 at 0:9:38 UTC. See the documentation of the Date datatype for details on date specifications like these.

Context:

The show command displays the location of the source after correcting for precession and nutation. The reported horizon coordinates do not take atmospheric refraction, telescope tilts or the telescope pointing model into account, so they will differ slightly from the actual target azimuths and elevations used by the control system.

More specifically, the displayed Right Ascension and Declination are the geocentric apparent equatorial coordinates of the source, the azimuth and elevation are the corresponding geocentric horizon coordinates of the source, and the galactic longitude and latitude are the geocentric apparent galactic coordinates of the source.