New FITS keywords in the primary header

General keywords in the primary header

Keyword nameValueDescription
RADECSYSFK5Celestial coordinate system
EQUINOX2000.Equinox of celestial coordinate system
OBSGEO-X5327395.9638Cartesian Coordinate X of telescope
OBSGEO-Y-1719170.4876Cartesian Coordinate Y of telescope
OBSGEO-Z3051490.766Cartesian Coordinate Z of telescope
ORIGINNOTSA Nordic Optical Telescope Scientific Association
CREATORNOT2MEF V1.4.4Version of FITS writing software
OBS_MODEImagingType of data (Imaging/Spectroscopy)
QCRDATE2004-11-24Instrument rotation centre reference date

The keywords OBSGEO-X, OBSGEO-Y, and OBSGEO-Y are the geocentric Cartesian triple incarnation of the traditional position on earth expressed in longitude, latitude, and altitude. These values were calculated based on GPS data for the location of the NOT.

Timing keywords in the primary header

For ALFOSC, STANCAM, MOSCA, FIES the start and midpoint of the actual exposure are recorded in ISO8601 format. For NOTCAM these keywords are not recorded in the primary header, but in the headers of the data extensions, since the different extensions have different start times, midpoints and exposure times.
Keyword nameValueDescription
DATE-OBS2003-09-26T02:25:56.0Start of exposure
DATE-AVG2003-09-26T02:26:26.0Midpoint of exposure

Special NOTCAM headers

To facilitate the amplifier-dependent data reduction for NOTCAM several keywords have been added to the primary header. Together with a special translation file these can be used to create multiextension format from images with multiple amplifier readouts recorded as sections of a single image.

New FITS keywords in data extensions

Mandatory keywords in data extensions

The new NOT data extensions have the following mandatory keywords with mandatory values:
Keyword nameValueDescription
XTENSIONIMAGEImage data extension
PCOUNT0Required keyword in data extension
GCOUNT1Required keyword in data extension

Additional keywords describing the data extensions

These optional keywords describe the data extension itself. Values listed are examples.
Keyword nameValueDescription
EXTNAMEim1Extension name
IMAGEID1ID of data extension

Primary WCS for imaging data

Keyword nameValueDescription
CTYPE1 RA---TAN Name of coordinate (RA, gnomonic projection)
CTYPE2 DEC--TAN Name of coordinate (Dec, Gnomonic projection)
CRVAL1 RA at reference point
CRVAL2 Dec at reference point
CUNIT1deg Unit of 1st axis
CUNIT2deg Unit of 2nd axis
CRPIX1 Reference pixel on 1st axis
CRPIX2 Reference pixel on 2nd axis
CD1_1 Element of transformation matrix for primary WCS
CD1_2 Element of transformation matrix for primary WCS
CD2_1 Element of transformation matrix for primary WCS
CD2_2 Element of transformation matrix for primary WCS

Linear pixel WCS for spectroscopic data

Keyword nameValueDescription
CTYPE1 X Coordinate name
CTYPE2 Y Coordinate name
CRVAL1 X at reference point
CRVAL2 Y at reference point
CUNIT1pixel Unit of 1st axis
CUNIT2pixel Unit of 2nd axis
CRPIX1 Reference pixel on 1st axis
CRPIX2 Reference pixel on 2nd axis
CDELT1Increment on 1st axis
CDELT2Increment on 2nd axis

Detector characteristics

Keyword nameValueDescription
QCDDATE Detector characteristics reference date
RDNOISE Read-out noise [e-]

Extra IRAF-style keywords

Keyword nameValueDescription
CCDNAME Name of detector, used by IRAF ccdproc, mscred
CCDSUM 1 1On chip binning factors, used by IRAF ccdproc, mscred
DATASECLocation of data pixels
TRIMSECSection of useful data
BIASSECLocation of bias pixels

Extra IRAF-style keywords for mosaic data

Keyword nameValueDescription
DETSECLocation in final mosaic
CCDSEC Location on CCD