NAME
moondist - calculates the effective angle between a target and the moon
SYNOPSIS
moondist [ut=hh:mm:ss] [date=dd/mm/yyyy] [verbose]
request_file |
fits_file
DESCRIPTION
This program calculates the position of the moon at the time of the
observation requested for each stanza in the request file for the upcoming
night. Alternatively, if a fits_file is specified it calculates the lunar
distance at the time of observation from the DATE-OBS and UT symols. The time
of observation is estimated in the following manner: if UTSTART is specified
this time is used; if an LSTSTART is specified, then the midpoint between
LSTSTART and LSTEND is used; if neither of these is used and an RA is
specified, the time of transit is used. If transit occurs before the sun is
10 degrees below the horizon, then the time of `sunset' is used. Similarly if
the transit occurs after `sunrise' the time of sunrise is
used.
We define here `the effective angle' as the lesser of the great circle
distance and the absolute value of the azimuth difference (in degrees)
between the target and the moon. We believe this number to be be a good
indicator of the amount of moonlight that will fall into the
slit.
The effective angular distance in degrees for all the stanzas in the request
file is printed to stdout and the program exits with a zero exit code. If the
moon is not a problem (or is below the horizon) or if the program is unable
to calculate the moon distance for any reason, such as missing RA it prints
the minimum distance so far calculated or one thousand degrees (whichever is
lower) and exits with a zero exit
code.
FLAGS
Note the ut and date options are meaningless when FITS files are used.
[ut=hh:mm:ss] - uses the Universal Time specified instead of the
derived Universal
Time.
[date=dd/mm/yyyy] - uses the universal date specified instead of today
(or more correctly
tonight).
[help] - displays options.
[verbose] - much more printout.
BUGS
No consideration is made for the case when an object transits more than once
in a given night. No weighting due to lunar phase is made even though the
moon is much brighter when near
full.