[fitsbits] BINTABLE convention for >999 columns

[Mohammad Akhlaghi]

Dear Mark,

Thank you very much for sharing this very interesting suggestion.

While reading the suggested convention, an idea occurred to me which I 
thought would be interesting just as a brainstorm.

Your suggestion does indeed increase the number of possible columns in a 
FITS table from 999 to 18574. But the fundamental problem still remains: 
there is a hard limit which will probably be reached for some applications.

Just as a fresh brainstorm, what do you think about this convention: 
removing the exact column identifier/number from the keyword name and 
instead relying on the keyword ordering. This will allow a 
(theoretically) unlimited number of columns, but will just rely on the 
order the keywords in the header (for each class/property, for example 
`TFORM' or `TTYPE').

In this suggestion, the table column property keywords would keep the 
`XXXXXnnn' keyword name convention. But we just allow a single 
`XXXXXNNN' (for example `TFORMNNN', or `TTYPENNN') which identifies the 
respective property of the "Next" column.

One advantage of the current and your suggested convention is that the 
order of the keywords in the header is irrelevant. Therefore the 
keywords can be read/written anywhere in the header. But with this 
suggestion, their reading and writing order (independent of the first 
999 keywords) matters. However, it allows the user/programmer to not 
worry about the number of columns and can be applied to ASCII and binary 
tables.

This was just a fast brainstorm which occurred to me after reading your 
suggestion. But if a similar case hasn't already been discussed here 
before, it may be an interesting alternative to think about. I am new to 
this mailing list and far less experienced than many of the people here, 
so please excuse my in-experience.

Thank you very much,
Mohammad


-- 
Postdoctoral research fellow,
Maintainer of GNU Astronomy Utilities (Gnuastro),
Centre de Recherche Astrophysique de Lyon (CRAL),
Observatoire de Lyon. 9, Avenue Charles André,
Saint Genis Laval (69230), France.