[fitsbits] Question on angstrom and erg units in FITS standard

[Thomas Robitaille]

Steve Allen wrote:
> On Tue 2014-11-04T18:10:39 +0100, Thomas Robitaille hath writ:
>>   Deprecated in IAU Style Manual (McNally 1988) but still in use.
>>
>> My question is, are these units deprecated in the FITS standard too? Or
>> is this one of the places where the FITS standard deviates from McNally
>> 1988?
>>
>> In short, should FITS readers/writers treat 'angstrom' and 'erg' as
>> deprecated?
> 
> Our instruments produce a lot of values with units like "degC",
> "degF", and others with unapproved units for values which are intended
> as engineering metadata as opposed to science metadata.  If we had
> enough resources (of both human labor and compute power in the
> devices) to characterize what those measurements mean and how they
> affect the science data then we would recast them in SI units.
> 
> In the case of angstrom and erg the conversion is simple enough that
> most hardware and software systems are probably able to recast them
> as nm and J, but the FITS standard writers recognize that may never
> happen for already-deployed instruments.
> 
> Deprecated is not forbidden.  The point of FITS is that the meaning of
> the file should be clear to the reader.  In the cases of angstrom and
> erg it is probably more important to put effort into documenting the
> reference frame and laboratory conditions than it is to convert to nm
> and J.

Thanks for your reply - but just to be clear, are angstrom and erg
*actually* deprecated in the FITS standard? That is, should a strict
writer emit a deprecation warning? It wasn't obvious to me whether the
fact the units are deprecated in McNally 1988 also means that the units
are deprecated in FITS?

Thanks,
Tom

> 
> --
> Steve Allen                 <sla at ucolick.org>                WGS-84 (GPS)
> UCO/Lick Observatory--ISB   Natural Sciences II, Room 165    Lat  +36.99855
> 1156 High Street            Voice: +1 831 459 3046           Lng -122.06015
> Santa Cruz, CA 95064        http://www.ucolick.org/~sla/     Hgt +250 m
> 
> _______________________________________________
> fitsbits mailing list
> fitsbits at listmgr.nrao.edu
> https://listmgr.nrao.edu/mailman/listinfo/fitsbits