NAME

moon - calculates lunar position

SYNOPSIS

moon [rise=] [set=] [iso=] [mode=geocentric | astrometric | topocentric |observed] [noelev] [debug]

DESCRIPTION

This program calculates the current topocentric position of the moon using a subset of Browns formulation (Brown, Ernest, W. Tables of the Motion of the Moon Yale Univ. Press 1919) as selected by Jerome Hudson. The rms error compared to positions found the Astronomical Almanac for 1990 appears to be on the order of .01 degree. This method is about ten times more accurate than the low precision formula quoted in the blue book. Unless the geocentric option is used the the position is corrected for lunar parallax; this term can be up to one degree.

The output contains a coordinate string like: 

ra=12:58:59.33 dec=-02:08:05.26 equinox=2017.572 epoch=2017.572 name=moon mode=topocentric phase=0.36 lunation=1170
Where the first two fields are the RA and Dec, the next is the coordinate equinox (read from the system clock), the fourth is the name of the object, the fifth is the number of degrees that the moon is above the horizon and the last is the illumination of the moon, where 0.0 is new and 1.0 is full. The lunation is the Brown lunation which differs from the Meuss by 953.

The program can also calculate the Universal time at which the moon reaches a given altitude. In this mode of operation, the output will be a single field in hh:mm:ss format. No corrections for refraction are made.

The observatory longitude is determined from the telescope server.

OPTIONS

iso= calculates the lunar coordinates and phase for the specified ISO date.

rise=# calculates Universal time when the moon's altitude rises to # degrees above the horizon.

set=# calculates Universal time when the moon's altitude is # degrees above the horizon as it is setting.

geocentric - computes the geocentric apparent position rather than the topocentric value.

elev - correct the time of setting for the effects of refraction, the fact that the moon has finite diameter and for the elevation of the observatory (taken from tel_status the telescope server).

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