Ambient temperature in degrees Celsius
Software that created the original FITS file.
DARKTIME appears in multiple conventions
Dew point in degrees Celsius
Electronic gain -- electrons per ADU
EQUINOX is now preferred over the old EPOCH
[s] Non-standard exposure time conventions.
EXTLEVEL and HDULEVEL are synonymous, but EXTLEVEL is part of the standard since 1.19
EXTNAME and HDUNAME are synonymous, but EXTNAME is part of the standard since 1.19
EXTVER and HDUVER are synonymous, but EXTVER is part of the standard since 1.19
Focus temperature in degrees Celsius.
Relative humidity in percent
Equivalent keywords for array column axis string parameters.
Equivalent keywords for array column axis parameter values.
Image rotation angle in degrees
Image scale (arcsec/pixel)
Atmospheric pressure in hPA
RADESYS is now preferred over the old RADECSYS
RESTFRQ is now preferred over the old RESTFREQ
Equivalent keywords for column coordinate transformation matrix (CD convention).
Clock time duration of observation.
Equivalent keywords for column coordinate transformation matrix (PC convention).
Equivalent keywords for column parameter names.
Variants for recording the start time of observation in HH:MM:SS[.s...] format
Variants for recording the ending time of observation in HH:MM:SS[.s...] format
Equivalent keywords for column parameter values.
Equivalent keywords for column coordinate transformation matrix (PC convention).
Wind direction in degrees, clockwise from North
Pixel binning in X direction
Pixel binning in Y direction