🚀 go-pugleaf

In article <1OCT199212490103@stars.gsfc.nasa.gov>, landsman@stars.gsfc.nasa.gov (Wayne Landsman (301)-286-3625) writes...

>    My current IDL FITS reader takes the NOST manual literally.   It
>only extracts the 20 characters in columns 11-30 to determine the FITS
>keyword value.    Any characters in columns 31-50 are interpreted as being
>the imaginary part of a complex number.
> 

This requirement applies only to fixed format.  The fixed format is
required only for values of mandatory keywords.  (At present, there
are no mandatory keywords with floating point values.)  For other
keyword values, it is recommended but not required.  See FITS Paper I,
which says "recommended, and partly required."  This language is
interpreted in 5.3.1 of the NOST standard by saying, "The fixed format
is required for values of mandatory keywords and recommended for all
others."  A well-recognized problem is that columns 11-30 do not
contain enough space to express the full precision of a double
precision floating point number.  The most common, but not standard or
required solution, is to extend the value beyond column 30.  A number
of proposed designs reviewed by the FITS office use this solution.  A
FITS reader that assumes that values of standard optional keywords or
user-defined keywords end in column 30 will not extract correct values
for some user-defined keywords in these data sets. 

Incidentally, EVERYBODY should be certain that their copy of the NOST
Standard is current.  The most recent version is 0.3b.  Some
misunderstandings have arisen because users are referring to 
superseded versions.

				Barry Schlesinger
				NOST FITS Support Office