The OBSVATON packet

The OBSVATON PDF defines a set of general header information which should be collected for all observations. The header records should appear as follows:

ORIGIN  = 'ING La Palma'     / Origin of data
OBSERVAT= 'LAPALMA'          / Origin of data
PDFVERSI=  CHAR              / headers specified by
HCTVERSI=  CHAR              / headers collected by
TELESCOP= 'WHT'              / Name of telescope
FSTATION=  CHAR              / Focal station 
INSTRUME=  CHAR              / Name of instrument configuration
DETECTOR=  CHAR              / Name of detector
OBSERVER=  CHAR              / Name of observer
PROPOSAL=  CHAR              / PATT/CAT reference
DATE-OBS= 'dd/mm/yy'         / Date of UT at start of observation 
RUN     =  INTEGER           / Run number of observation
OBJECT  =  CHAR              / Title of observation
OBSTYPE =  CHAR              / Type of observation
IMAGETYP=  CHAR              / Type of observation
CTYPE1  =  CHAR              / Units of x axis
CRPIX1  =                  1 / Reference pixel is # 1
CRVAL1  =  REAL              / Axis value at reference pixel
CDELT1  =  REAL              / Interval between pixel centres
CTYPE2  =  CHAR              / Units of y axis 
CRPIX2  =                  1 / Reference pixel is # 1
CRVAL2  =  REAL              / Axis value at reference pixel
CDELT2  =  REAL              / Interval between pixel centres
DISPAXIS= INTEGER            / Axis in dispersion direction

Notes:

• The PDFVERSI keyword is used to define the version of the PDFs used in creating the current dataset. This should be equal to the name of the CMS class defining this version. Similarly, HCTVERSI holds the name of the class of the Header-Collection task.

• The values for FSTATION should be `Cassegrain', `Nasmyth D' (for Nasmyth drive-side) and `Nasmyth CW' (for Nasmyth counterweight side) or `Prime'.

• The OBJECT keyword holds a descriptive (and optional) title for the observation. The exact name of the target (as specified in the TCS catalogue) is held in the CATNAME keyword of the TELESCOP packet.

• The keyword RUN was chosen for compatibility with AAO; the alternative was NUMRUN.

• DATE-OBS, with the 8-character format noted above, is a standard FITS keyword. AAO prefer UTDATE with the format `yyyy:mm:dd' in order to record the century.

• The axis headers are intended to provide an approximate wavelength calibration. For axes where no useful information is available, the headers can either be omitted or the pixel numbers used as the coordinate.

• There is no axis for the $z$ direction. With the existing WHT instruments, the $z$ axis either has no units but pixels (continuous-mode observing) or is related to wavelength in a way too complex to be described by the standard keywords (Taurus spectroscopy).

• OBSVERVAT and IMAGETYP duplicate ORIGIN and OBSTYPE. The extra keywords are required by IRAF.

• DISPAXIS is required by IRAF.