FITS Keyword Dictionary: Spectroscopic Aperture Subset

This keyword dictionary defines keywords which may be used in in describing spectroscopic apertures as discussed in Description of 2D Spectroscopic Image Data. The full dictionary is NOAO FITS Keyword Dictionary: Version 1.0 - January 2000.

Each keyword definition has the following fields.

NAME

The logical class name as given in Classes Describing Astronomical Observations.

KEYWORD

The FITS keyword(s). Typically if there is more than one keyword, the first will be the keyword to use when there is just one value and the second is an indexed version when there are multiple values. The syntax for indexed keywords is described below. Occasionally there will be more than one unindexed choice with the second choice provided to agree with a keyword currently in use though not the preferred name as defined by the dictionary.

DEFAULT

Keyword or value which is applicable when the primary keyword is missing. If there is no default the value "none" is given. When there are multiple primary keywords there will be a matching number of defaults. When both the primary and default have indices then the index value is the same. A common case is when the indexed primary keywords default to the unindexed version of the primary keyword. This occurs when the information is the same for all elements of an indexed class. If the unindexed keyword is also missing it would then default to the specified keyword for it. For example, in the case that there are multiple objects described in the header, the epoch keywords are defined to be OEPO0001, OEPO0002, etc. These will likely all have the same value so they would not be used in favor of the unindexed keyword OBJEPOCH as shown by the DEFAULT field. But it is also likely that all coordinates specified in the header have the same epoch. So it is possible to not use OBJEPOCH in which case its default is EPOCH. It is recommended, however, that if a class of indexed keywords is used then at least the single value keyword be included. In the example this would be OBJEPOCH to go with the ORA%d/ODEC%d indexed keywords.

INDEX

Index values for indexed keywords. When there are multiple keywords there will be multiple index values. If the keyword has multiple indices the values apply from left to right. There are two types of index values, a numeric range for 'd' indices and a character class for 'c' indices. Numeric ranges are of the form M-N where M and N are integers with M<=N. Character classes are of the form [cc-c] where the c are characters (from the allowed FITS keyword character set and ranges in ascii order are given as c-c. For example,

    1-99       Integers from 1 to 99
    [A-Z]      Capital alphabetic characters from A to Z
    [i0-9A-Z]  i, followed by 0 to 9, followed by A to Z

HDU

A recommendation for whether the keyword should be part of the primary or extension header-data unit when image extensions are used with multiple amplifiers and CCDs. For a single amplifier observation there is only a primary header with data and the HDU recommendation is not applicable.

primary - primary header
extension - extension header
primary & extension - primary and extension headers
primary | extension - if there is only one CCD or all values are the same place in the primary header otherwise place in the extension header.

VALUE

The format of the value field. The format descriptions are those used by IRAF and are described below. The numeric formats also indicate a numeric FITS keyword value and other formats indicate string keyword values. Special types of value formats are indicated in parenthesis. These include 'date' for a FITS date string, 'checksum' for a FITS checksum string, 'datasum' for a FITS datasum string, and 'section' for an image section string.

UNITS

Expected or suggested units for the value. These are either explicit units or a keyword that specifies the unit.

COMMENT

The default comment in a FITS card. This is only a default and a more appropriate and detailed comment may be used.

EXAMPLE

An example keyword value.

DESCRIPTION

The description of the keyword and logical parameter.

Notes:

The index patterns in the KEYWORD and DEFAULT entries have the forms "%Nd" and "%c". The first form is a decimal integer which has the minimum length given by the value of N (N = 1 if missing). The number is padded with leading zeros to the specified minimum number of places. The second form expands to a single character from the set of index characters. For example,
```
    KEY%4d with range 1-99 produces KEY0001 to KEY0099
    KEY%d with range 1-99 produces KEY1 to KEY99
    KEY%c with range [A-Z] produces KEYA to KEYZ
```

The value formats in the VALUE entry have the form "%w.dC", where w is the field width, d is the number of decimal places or the number of digits of preceision, and C is the format code. The w and d fields are optional. The format codes are as follows:

        b       boolean (T or F)
        c       single character (c or '\c' or '\0nnn')
        d       decimal integer
        e       exponential format (D specifies the precision)
        f       fixed format (D specifies the number of decimal places)
        g       general format (D specifies the precision)
        h       hms format (hh:mm:ss.ss, D = no. decimal places)
        H       h format with value divided by 15
        m       minutes, seconds (or hours, minutes) (mm:ss.ss)
        M       m format with value divided by 15
        o       octal integer
        s       string (D field specifies max chars to print)
        u       unsigned decimal integer
        x       hexadecimal integer
        z       complex format (r,r) (D = precision)

Conventions for W (field width) specification:

    W =  n      right justify in field of N characters, blank fill
        -n      left justify in field of N characters, blank fill
        0n      zero fill at left (only if right justified)
    absent, 0   use as much space as needed (D field sets precision)

These are the same as the IRAF formats except that %b produces the FITS 'T' or 'F' logical value.

When the acquisition TV and the guider TV are the same the acquisition TV keywords are used.
Sensor positions may be given as two values for x,y positions.


NAME:         Observation.title
KEYWORD:      OBJECT
DEFAULT:      none
INDEX:        none
HDU:          primary & extnsion
VALUE:        %s
UNITS:        
COMMENT:      Observation title
EXAMPLE:      'm51 V 600s'
DESCRIPTION:
    The observation title given by the observer.  This will sometimes be
    the name of the astronomical target object but often it is not or has
    additional information so the standard object name(s) should be given
    by the OBJNAME keyword(s).


NAME:         Object[n].name
KEYWORD:      OBJNAME OBJ%4d
DEFAULT:      OBJECT OBJNAME
INDEX:        none 1-9999
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Target object
EXAMPLE:      'M 51    '
DESCRIPTION:
    Standard reference or catalog name for the target astronomical
    object(s).  The name should follow IAU standards.  These keywords
    differ from the OBJECT keyword which is used to identify the
    observation.


NAME:         Object[n].type
KEYWORD:      OBJTYPE OBJT%4d
DEFAULT:      none OBJTYPE
INDEX:        none 1-9999
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Type of object
EXAMPLE:      'galaxy  '
DESCRIPTION:
    Type of target astronomical object(s).  This is taken from a dictionary
    of names yet to be defined.  Some common types are 'galaxy', 'star',
    and 'sky'.  If not particular object is targeted the type 'field'
    may be used.


NAME:         Object[n].Coordinate.Equatorial.ra
KEYWORD:      OBJRA ORA%4d
DEFAULT:      RA none
INDEX:        none 1-9999
HDU:          primary
VALUE:        %h
UNITS:        OBJRAU ORAU%4d
COMMENT:      Right ascension of object
EXAMPLE:      '13:29:24.00'
DESCRIPTION:
    Right ascension of the target astronomical object(s).


NAME:         Object[n].Coordinate.Equatorial.dec
KEYWORD:      OBJDEC ODEC%4d
DEFAULT:      DEC none
INDEX:        none 1-9999
HDU:          primary
VALUE:        %h
UNITS:        OBJDECU ODEU%d
COMMENT:      Declination of object
EXAMPLE:      '47:15:34.00'
DESCRIPTION:
    Declination of the target astronomical object(s).


NAME:         Coordinate.raunit
KEYWORD:      RAUNIT
DEFAULT:      UNITRA
INDEX:        none
HDU:          primary & extension
VALUE:        %s
UNITS:        
COMMENT:      Right ascension unit
EXAMPLE:      'hr'
DESCRIPTION:
    Default right ascension units.


NAME:         Coordinate.decunit
KEYWORD:      DECUNIT
DEFAULT:      UNITDEC
INDEX:        none
HDU:          primary & extension
VALUE:        %s
UNITS:        
COMMENT:      Declination unit
EXAMPLE:      'deg'
DESCRIPTION:
    Default declination units.


NAME:         Object[n].Coordinate.Equatorial.epoch
KEYWORD:      OBJEPOCH OEPO%4d
DEFAULT:      EPOCH OBJEPOCH
INDEX:        none 1-9999
HDU:          primary
VALUE:        %g
UNITS:        'yr'
COMMENT:      Epoch of object coordinates
EXAMPLE:      1950.0
DESCRIPTION:
    Epoch of the target astronomical object coordinate(s).  This is given
    in years.


NAME:         Coordinate.system
KEYWORD:      RADECSYS
DEFAULT:      'FK5'
INDEX:        none
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Default coordinate system
EXAMPLE:      'FK5     '
DESCRIPTION:
    Default coordinate system type.  If absent the default value is 'FK5'.


NAME:         Coordinate.equinox
KEYWORD:      EQUINOX
DEFAULT:      2.
INDEX:        none
HDU:          primary & extension
VALUE:        %g
UNITS:        'yr'
COMMENT:      Default coordinate equinox
EXAMPLE:      2000.0
DESCRIPTION:
    Default coordinate system equinox.  A value before 1984 is Besselian
    otherwise it is Julian.  If absent the default is J2000.


NAME:         Aperture[n].apertureid
KEYWORD:      APERTURE APER%4d
DEFAULT:      none APERTURE
INDEX:        none 1-9999
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Aperture identification
EXAMPLE:      'Mask 12345'
DESCRIPTION:
   Aperture identification.  This can be a physical aperture identification,
   the name of a mask, a fiber configuration, etc.  When there are many
   apertures the keyword APERTURE may be used to specify a configuration
   or mask identification and the APER%4d keywords can be used to identify
   some information about the aperture such as a fiber number.


NAME:         Aperture[n].aperturetype
KEYWORD:      APTYPE APTY%4d
DEFAULT:      none APTYPE
INDEX:        none 1-9999
HDU:          primary
VALUE:        %s (dictionary)
UNITS:        
COMMENT:      Aperture type
EXAMPLE:      'hexlens+fiber'
DESCRIPTION:
   Aperture type.  This is an from a dictionary.  The common types are
   "slit", "hole", "fiber", "hexlens", "hexlens+fiber" and "none".  The
   last type is for aperture-less spectroscopy such as with objective
   prisms.  Typically for multiobject spectroscopy all the aperture types
   will be the same and the keyword will be APTYPE.


NAME:         Aperture[n].diameter
KEYWORD:      APERDIA APDI%4d
DEFAULT:      none APERDIA
INDEX:        none 1-9999
HDU:          primary
VALUE:        %g
UNITS:        APUNIT
COMMENT:      Aperture diameter
EXAMPLE:      1.
DESCRIPTION:
    Aperture diameter of the aperture(s) for circular apertures and
    fibers.  This is also used as an approximation to the size
    of hexagonal lenses.


NAME:         Aperture[n].length
KEYWORD:      APERLEN APLE%4d
DEFAULT:      none APERLEN
INDEX:        none 1-999
HDU:          primary
VALUE:        %g
UNITS:        APUNIT
COMMENT:      Slit length
EXAMPLE:      10.
DESCRIPTION:
    Aperture length of the aperture(s) for slit apertures.


NAME:         Aperture[n].width
KEYWORD:      APERWID APWI%4d
DEFAULT:      none APERWID
INDEX:        none 1-9999
HDU:          primary
VALUE:        %g
UNITS:        APUNIT
COMMENT:      Slit width
EXAMPLE:      1.
DESCRIPTION:
    Aperture width of the aperture(s) for slit apertures.


NAME:         Aperture[n].apunit
KEYWORD:      APUNIT APUN%4d
DEFAULT:      UNITAP APUNIT
INDEX:        none 1-9999
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Aperture dimension unit
EXAMPLE:      'arcsec  '
DESCRIPTION:
    Units of aperture dimensions.  This applies to slit widths and lengths,
    fiber diameters, lenslet diameters, etc.  It may be a physical dimension
    or a projected angle on the sky.


NAME:         Aperture[n].posangle
KEYWORD:      APERPA APPA%4d
DEFAULT:      none APERPA
INDEX:        none 1-9999
HDU:          primary
VALUE:        %g
UNITS:        APPAUNIT
COMMENT:      Aperture position angle
EXAMPLE:      90.0
DESCRIPTION:
    Aperture position angle of the aperture(s) on the sky.  This is
    measured using the longest dimension from north to east for slits.
    For hexagonal lenslets it gives the position angle for one of
    the sides.


NAME:         Aperture[n].paunit
KEYWORD:      APPAUNIT APAU%4d
DEFAULT:      PAUNIT APPAUNIT
INDEX:        none 1-9999
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Aperture position angle unit
EXAMPLE:      'deg    '
DESCRIPTION:
    Aperture position angle unit.


NAME:         Aperture[n].Coordinate.Equatorial.ra
KEYWORD:      APRA ARA%4d
DEFAULT:      OBJRA ORA%4d
INDEX:        none 1-9999
HDU:          primary
VALUE:        %h
UNITS:        APRAU ARAU%4d
COMMENT:      Aperture right ascension
EXAMPLE:      '13:29:24.00'
DESCRIPTION:
    Right ascension of the aperture(s).


NAME:         Aperture[n].Coordinate.Equatorial.dec
KEYWORD:      APDEC ADEC%4d
DEFAULT:      OBJDEC ODEC%4d
INDEX:        none 1-9999
HDU:          primary
VALUE:        %h
UNITS:        APDECU ADEU%4d
COMMENT:      Aperture declination
EXAMPLE:      '47:15:34.00'
DESCRIPTION:
    Declination of the aperture(s).


NAME:         Aperture[n].Coordinate.Equatorial.epoch
KEYWORD:      APEPOCH AEPO%4d
DEFAULT:      OBJEPOCH OEPO%4d
INDEX:        none 1-9999
HDU:          primary
VALUE:        %g
UNITS:        'yr'
COMMENT:      Aperture coordinate epoch
EXAMPLE:      1950.0
DESCRIPTION:
    Epoch of the coordinates for the aperture(s).


NAME:         Aperture[n].Spectrum.Wcs.ctype[1]
KEYWORD:      CTYPE1 CTY1%4d
DEFAULT:      'LINEAR' CTYPE1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %s
UNITS:        
COMMENT:      Spectrum coordinate type
EXAMPLE:      'WAVE-WAV'
DESCRIPTION:
    Spectrum dispersion coordinate type.  These are the FITS defined types.


NAME:         Aperture[n].Spectrum.Wcs.ctype[2]
KEYWORD:      CTYPE2 CTY2%4d
DEFAULT:      'LINEAR' CTYPE2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %s
UNITS:        
COMMENT:      Spectrum coordinate type
EXAMPLE:      'LINEAR  '
DESCRIPTION:
    Spectrum cross-dispersion coordinate type.  These are the FITS
    defined types.


NAME:         Aperture[n].Spectrum.Wcs.crpix[1]
KEYWORD:      CRPIX1 CRP1%4d
DEFAULT:      none CRPIX1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        'pixel' 'pixel'
COMMENT:      Spectrum center
EXAMPLE:      1024.0
DESCRIPTION:
    Reference spectrum pixel coordinate.  Generally this should be the at
    the center of the spectrum.  In raw data the spectrum position(s) may be
    predicted apart from an offset that will be determined during data
    reduction.


NAME:         Aperture[n].Spectrum.Wcs.crpix[2]
KEYWORD:      CRPIX2 CRP2%4d
DEFAULT:      none CRPIX2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        'pixel' 'pixel'
COMMENT:      Spectrum center
EXAMPLE:      1024.0
DESCRIPTION:
    Reference spectrum pixel coordinate.  Generally this should be the at
    the center of the spectrum.  In raw data the spectrum position(s) may be
    predicted apart from an offset that will be determined during data
    reduction.


NAME:         Aperture[n].Spectrum.Wcs.crpix[1]
KEYWORD:      CRPIX1 CRP1%4d
DEFAULT:      none CRPIX1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        'pixel' 'pixel'
COMMENT:      Spectrum center
EXAMPLE:      1024.0
DESCRIPTION:
    Reference spectrum pixel coordinate.  Generally this should be the at
    the center of the spectrum.  In raw data the spectrum position(s) may be
    predicted apart from an offset that will be determined during data
    reduction.


NAME:         Aperture[n].Spectrum.Wcs.crpix[2]
KEYWORD:      CRPIX2 CRP2%4d
DEFAULT:      none CRPIX2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        'pixel' 'pixel'
COMMENT:      Spectrum center
EXAMPLE:      1024.0
DESCRIPTION:
    Reference spectrum pixel coordinate.  Generally this should be the at
    the center of the spectrum.  In raw data the spectrum position(s) may be
    predicted apart from an offset that will be determined during data
    reduction.


NAME:         Aperture[n].Spectrum.Wcs.cd[1,1]
KEYWORD:      CD1_1 CD11%4d
DEFAULT:      1. CD1_1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT1/pixel CUN1%4d/pixel
COMMENT:      Spec coord matrix
EXAMPLE:      1.0
DESCRIPTION:
    Spectrum coordinate matrix.  World coordinate axis 1 is defined
    to be the dispersion and the other axes are spatial.  The matrix
    implies a dispersion axis in the image coordinates.


NAME:         Aperture[n].Spectrum.Wcs.cd[1,2]
KEYWORD:      CD1_2 CD12%4d
DEFAULT:      0. CD1_2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT1/pixel CUN1%4d/pixel
COMMENT:      Spec coord matrix
EXAMPLE:      0.0
DESCRIPTION:
    Spectrum coordinate matrix.  World coordinate axis 1 is defined
    to be the dispersion and the other axes are spatial.  The matrix
    implies a dispersion axis in the image coordinates.


NAME:         Aperture[n].Spectrum.Wcs.cd[2,1]
KEYWORD:      CD2_1 CD21%4d
DEFAULT:      0. CD2_1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT2/pixel CUN2%4d/pixel
COMMENT:      Spec coord matrix
EXAMPLE:      0.0
DESCRIPTION:
    Spectrum coordinate matrix.  World coordinate axis 1 is defined
    to be the dispersion and the other axes are spatial.  The matrix
    implies a dispersion axis in the image coordinates.


NAME:         Aperture[n].Spectrum.Wcs.cd[2,2]
KEYWORD:      CD2_2 CD22%4d
DEFAULT:      1. CD2_2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT2/pixel CUN2%4d/pixel
COMMENT:      Spec coord matrix
EXAMPLE:      1.0
DESCRIPTION:
    Spectrum coordinate matrix.  World coordinate axis 1 is defined
    to be the dispersion and the other axes are spatial.  The matrix
    implies a dispersion axis in the image coordinates.


NAME:         Aperture[n].Spectrum.Wcs.Coordinate.Spec2d.dispval
KEYWORD:      CRVAL1 CRV1%4d
DEFAULT:      none CRVAL1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT1 CUN1%4d
COMMENT:      Spectrum dispersion center
EXAMPLE:      5015.0
DESCRIPTION:
    Spectrum reference dispersion coordinate corresponding to the spectrum
    reference pixel coordinate.  Note that by definition WCS axis 1 is
    always the dispersion axis.  The mapping of this WCS axis to the
    dispersion direction in the image is given by the coordinate
    transformation matrix keywords.  In raw data the reference dispersion
    coordinate may be approximately predicted.  This will be refined during
    data reductions.


NAME:         Aperture[n].Spectrum.Wcs.Coordinate.Spec2d.crossval
KEYWORD:      CRVAL2 CRV2%4d
DEFAULT:      none CRVAL2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT2 CUN2%4d
COMMENT:      Spectrum cross-dispersion center
EXAMPLE:      0.
DESCRIPTION:
    Spectrum reference cross-dispersion coordinate corresponding to the
    spectrum reference pixel coordinate.  Note that by definition WCS axis
    2 is always the cross-dispersion axis.  The mapping of this WCS axis to
    the cross-dispersion direction in the image is given by the coordinate
    transformation matrix keywords.  In raw data the reference
    cross-dispersion coordinate may be approximately predicted.  This will
    be refined during data reductions.


NAME:         Aperture[n].Spectrum.Wcs.dispunit
KEYWORD:      CUNIT1 CUN1%4d
DEFAULT:      DISPUNIT CUNIT1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %s
UNITS:        
COMMENT:      Spectrum coordinate unit
EXAMPLE:      'Angstrom'
DESCRIPTION:
    Spectrum dispersion coordinate unit.


NAME:         Aperture[n].Spectrum.Wcs.crossunit
KEYWORD:      CUNIT2 CUN2%4d
DEFAULT:      CROSUNIT CUNIT2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %s
UNITS:        
COMMENT:      Spectrum coordinate unit
EXAMPLE:      'arcsec'
DESCRIPTION:
    Spectrum corss-dispersion coordinate unit.


NAME:         Aperture[n].Spectrum.Wcsregion.wcsmin[1]
KEYWORD:      CMIN1 CMN1%4d
DEFAULT:      none CMIN1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT1 CUN1%4d
COMMENT:      Spectrum dispersion limit
EXAMPLE:      3000.0
DESCRIPTION:
    Dispersion limit for the region occupied by the spectrum.


NAME:         Aperture[n].Spectrum.Wcsregion.wcsmax[1]
KEYWORD:      CMAX1 CMX1%4d
DEFAULT:      none CMAX1
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT1 CUN1%4d
COMMENT:      Spectrum dispersion limit
EXAMPLE:      6000.0
DESCRIPTION:
    Dispersion limit for the region occupied by the spectrum.


NAME:         Aperture[n].Spectrum.Wcsregion.wcsmin[2]
KEYWORD:      CMIN2 CMN2%4d
DEFAULT:      none CMIN2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT2 CUN2%4d
COMMENT:      Spectrum cross-dispersion limit
EXAMPLE:      -1.0
DESCRIPTION:
    Cross-dispersion limit for the region occupied by the spectrum.


NAME:         Aperture[n].Spectrum.Wcsregion.wcsmax[2]
KEYWORD:      CMAX2 CMX2%4d
DEFAULT:      none CMAX2
INDEX:        none 1-9999
HDU:          extension
VALUE:        %g
UNITS:        CUNIT2 CUN2%4d
COMMENT:      Spectrum cross-dispersion limit
EXAMPLE:      1.0
DESCRIPTION:
    Cross-dispersion limit for the region occupied by the spectrum.


NAME:         Coordinate.ra
KEYWORD:      RA
DEFAULT:      none
INDEX:        none
HDU:          primary & extension
VALUE:        %h
UNITS:        RAUNIT
COMMENT:      Right ascension
EXAMPLE:      '13:29:24.00'
DESCRIPTION:
    Default right ascension.


NAME:         Coordinate.dec
KEYWORD:      DEC
DEFAULT:      none
INDEX:        none
HDU:          primary & extension
VALUE:        %h
UNITS:        DECUNIT
COMMENT:      Declination
EXAMPLE:      '47:15:34.00'
DESCRIPTION:
    Default declination.


NAME:         Units.ra
KEYWORD:      UNITRA
DEFAULT:      'hr'
INDEX:        none
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Right ascension unit
EXAMPLE:      'hr'
DESCRIPTION:
    Right ascension unit.


NAME:         Units.dec
KEYWORD:      UNITDEC
DEFAULT:      'deg'
INDEX:        none
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Declination unit
EXAMPLE:      'deg'
DESCRIPTION:
    Delination unit.


NAME:         Coordinate.epoch
KEYWORD:      EPOCH
DEFAULT:      MJD-OBS
INDEX:        none
HDU:          primary
VALUE:        %g
UNITS:        'yr'
COMMENT:      Default coordinate epoch
EXAMPLE:      1987.257752
DESCRIPTION:
    Default coordinate epoch.  The default is the epoch of date for the
    observation as derived from the MJD-OBS keyword.


NAME:         Coordinate.Spec2d.dispunit
KEYWORD:      DISPUNIT
DEFAULT:      'Angstrom'
INDEX:        none
HDU:          primary & extension
VALUE:        %s
UNITS:        
COMMENT:      Dispersion coordinate unit
EXAMPLE:      'Angstrom'
DESCRIPTION:
    Default dispersion coordinate unit.


NAME:         Coordinate.Spec2d.crossunit
KEYWORD:      CROSUNIT
DEFAULT:      'arcsec'
INDEX:        none
HDU:          primary & extension
VALUE:        %s
UNITS:        
COMMENT:      Declination unit
EXAMPLE:      'arcsec'
DESCRIPTION:
    Default cross dispersion unit.


NAME:         Units.aperture
KEYWORD:      UNITAP
DEFAULT:      'arcsec'
INDEX:        none
HDU:          primary
VALUE:        %s
UNITS:        
COMMENT:      Aperture size unit
EXAMPLE:      'arcsec'
DESCRIPTION:
    Focal plane aperture size unit.