[AstroPy] Re: HIERARCH

Joe Harrington jh at oobleck.astro.cornell.edu
Wed Mar 30 17:46:28 CST 2005

>I have no idea how many astronomers use ESO data and how many of 
>them do access the HIERARCH keywords.

I would estimate the number as roughly all the observational
astronomers in Europe and Chile, plus Americans and others like me who
collaborate with them.  Since the Europeans have comparatively few
spacecraft, a larger fraction is ground-based observers than in the

In their headers, almost all the useful info is in the HIERARCH
keywords.  Airmass, position of the telescope, observing conditions,
wavelength, image scale, etc.  They do give time and exposure time in
the regular keywords.  There are over 400 keywords in their headers,
of which about 30 are not HIERARCH keywords.  See
for an example.

>hdu.header['very long keyword']='a new value'

I just don't understand why this presents any problem to python.  If
the keyword starts with "HIERARCH", turn off length checking and treat
it like any other keyword, wherever length is checked.  What am I


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