[AstroPy] A simple python module, wrapping pytfits+matplotlib: fits I/O + graphic/display environment

James Turner jturner at gemini.edu
Fri May 5 11:59:56 CDT 2006


Hi Perry,

>> to disk, 2) you need to propagate headers, variance extensions etc.,
> 
> Note that 2) is a common desire, but think about how easy it is in 
> practice. When presented with two headers with conflicting header info, 
> which does one use, the first,  or some combination when adding two fits 
> files? This is always much harder to do well in practice.

For me, I suppose the key thing is to have enough of the header info
available to support methods that do things like WCS transformations or
whatever. For that particular case, I think it should be possible to ensure
that the values are always correct for the output.

More generally, with the Gemini data reduction software, we usually just
pass through all the useful miscellaneous keywords from the first header
when combining several input files (we also name the combined output file
after the first input file number, but with a suffix like "_add"). I
suppose that does mean that things like time stamps will not be as
meaningful as they should be, but it seems to work well enough in practice.

Of course the Gemini reduction process is a relatively special,
well-defined case - I'm sure you have to deal with much more general
problems (I'm just a humble astronomer, if there is such a thing) - but
I still think that even simplistic functionality in this area would be
useful in practice.

Cheers,

James.

-- 
James E.H. Turner
Gemini Observatory Southern Operations Centre,
Casilla 603,		Tel. (+56) 51 205609
La Serena, Chile.	Fax. (+56) 51 205650



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