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Non-standard keywords

Besides the standard FITS keywords defined in the FITS documents, it is possible to use other, non-standard keywords. Such non-standard keywords have no global definition and may be interpreted differently by different FITS readers.

A number of non-standard keywords has been used by ESO e.g. for definition of frames acquired at the La Silla observatory. They are given in Table 7.1.3 and should not be used with other definitions. An extended set of FITS keywords are defined for describing data from the VLT (see [7]).

 
Table 7.4: Name translation between special non-standard FITS keywords and MIDAS descriptors.
FITS keyword Data type MIDAS descriptor Remarks
MJD-OBJ Real O_TIME(4) Modified Julian Date of start of exposure
TM-START Real O_TIME(5) UT of start of exposure, in sec. after midnight
TM-END Real - UT of end of exposure
EXPTIME Real O_TIME(7) Exposure time in sec.
RA Real O_POS(1) Right Ascension in degrees
DEC Real O_POS(2) Declination in degrees
POSTN-RA Real O_POS(1) Right Ascension in degrees
POSTN-DE Real O_POS(2) Declination in degrees
AIRMASS Real O_AIRM Mean airmass of exposure
FILENAME String FILENAME Original file name
ESO-LOG String ESO-LOG Observing log
 

Due to the freedom to use non-standard keywords it is important to know their exact definitions when transferring data between different systems.


next up previous contents index
Next: Hierarchical keywords Up: FITS keywords Previous: Standard keywords
Petra Nass
1999-06-09