Utypes 0.4 comments

[Paul Harrison]

On 2009-11 -25, at 17:05, Norman Gray wrote:

>
> Rob,
>
> On 2009 Nov 25, at 16:55, Rob Seaman wrote:
>
>>> For example, we might imagine utypes appearing in a FITS file like:
>>>
>>> PFX01SSA= http://www.ivoa.net/...
>>> PFX02STC= http://www.ivoa.net/...
>>> UTYPE001= ssa:blah
>>> ...
>>>
>>> (see also Jonathan's suggestions in <http://www.ivoa.net/forum/dm/0610/1257.htm 
>>> >).  But something like that would impose length limits on the  
>>> sizes of prefixes and utypes as a whole: 'ssa:blah' could be at  
>>> most 72 characters.
>>
>> Presumably these would be represented as string valued keywords, in  
>> which case the limit is 68 characters.  An 80 character (ASCII  
>> 20-7E) card image total, minus 8 characters for the keyword, minus  
>> 2 characters for the value indicator (blank-equals), minus the 2  
>> single quotes around the string literal.
>
> Garhhh.  Arithmetic was never my strong point.  I'd forgotten about  
> the quotes, but even then, 80 - 8 - 2 != 72...
>
Ugly as hell, but there is the CONTINUE convention http://fits.gsfc.nasa.gov/registry/continue_keyword.html 
  so there is no length limit imposed by FITS.

Cheers
	Paul.