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Keyword entries

The keyword lines are of the format

<keyword> <value>

and the currently recognized keywords are

CENtre * The Right Ascension and declination of the field centre in sexagesimal format (as above). The coordinates must be in the same equinox as the coordinate list.

EQuinox * The equinox of the coordinate system used, in years. This MUST NOT be prefixed by B or J (eg neither B1950 nor J2000 is understood; use 1950 and 2000 instead).

EPoch * The epoch of observation, in years e.g. 1992.85.

PA The APPARENT PLACE position angle of the mask in degrees measured from north towards the east. This is equal to the positional angle of a slit at the field centre. However, since all slits are parallel to the Y axis and sky coordinates are non-cartesian, there will be some rotation of position angles away from the field centre. Default = 0.0 (ie North-South slits).

SLObj The slit length for objects with a blank slit length field. Default is set by the LEXT global MINSLITLEN in arcsec.

SLFid The diameter of fiducial star holes which have a blank slit length field. Default is set by the LEXT global FIDUCDIAM in arcsecs.

WDEF The slit growing weight for objects with a blank weight field. Default is 1.0

OFFDefault The offset of the slit centre from the object position along the Y axis, for objects with a blank offset field. Default is 0.0.

MMUNit The scale in mm/units at the focal plane for slit lengths, and offsets used in this file. This includes the values for SLO, SLF, and OFFD. Default is the mm/arcsec scale of the telescope as given by the reciprocal of the LEXT global SCALE, i.e. MMUNIT = 1/ SCALE. If SCALE is not specified the mm/arcsec scale for the AAT Cassegrain focus is used.

Only the capitalized letters are required for the keywords (although they do not have to be capitalized in the file). Extra letters beyond those capitalized above are not considered, so that ``SLOW_and_easy", ``Equus_the_horse", and ``epping_boys_high" will be interpreted as the ``SLObj", ``EQuinox", and ``EPoch" keywords respectively. Keyword lines marked with a * are required. If they are not in the file values are prompted for when the file is read by READ/CAT.