[fitsbits] Viewing .fts flies

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On Mon, 5 Mar 2007 Jimmybobs at gmail.com wrote:

> I've got a load of .fts files (from the SOHO archive) that I need to

Are they really FITS or something else ? Are they solar data ?
Are they FITS images or binary tables ?

> programs- is this right? Are they the same? I've been trying to use a
> program called ds9, but to no avail. 

ds9 is a FITS image viewer, extensively used at least in the high energy 
astrophysics community. What kind of problems do you have with it ?

If your files are not images, ds9 is not the tool for you. fv can be 
used to view FITS (binary) tables (and can also display images and view 
headers).

I have no idea about solar images, and their WCS compliance, but I guess 
ds9 will open an image in image pixels if there is no valid WCS (it does 
if there is no WCS at all).

I generally use an extremely lightweight shell script (fitshead by
Steve Allen of lick.ucsc.edu) for quick inspection of a FITS file. 
Namely I use "fitshead -x file | more" and then I can easily smell what 
the file (plain image, binary table, other extension). Ask if you need 
any clue.

FITS files start with "SIMPLE  =                    T" in their first 
80 bytes. If your .fts file has not such keyword, it is not FITS.

The rest of the keywords in the ASCII header allows to tell what the 
file is. That's rather easy if one knows where his towel is. But as a 
rule of thumb, if it has NAXIS not zero (usually 2) it is an image (or 
at least contains an image in the primary HDU). If it has NAXIS=0 and 
EXTEND=T the primary HDU is empty, and extension HDU follows (which can 
be a binary table, or ascii table or even an image extension).

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