Astro::FITS::HdrTrans module
----------------------------

What is it?
-----------
Astro::FITS::HdrTrans and associated sub-classes are tools for translating 
instrument-specific FITS headers into generically named headers.

Requirements
------------
The Astro::FITS::HdrTrans module has minimal requirements on other 
modules; only Carp and Time::Piece are required. Instrument-specific
sub-classes of Astro::FITS::HdrTrans may require other modules to be
installed, depending on the transformations those sub-classes make.
As an example, the translation sub-class for IRIS2 (an imaging
spectrometer used at the Anglo-Australian Telescope) requires
Math::Trig in order to do zenith distance to airmass translations.

Adding Subclasses
-----------------
Adding subclasses to do translations for other instruments should
be fairly straight-forward. The first step is writing an appropriate
valid_class function that returns true or false depending on the
contents of the header passed to it. You must come up with a unique
way of figuring out if the header is one that your subclass will
translate; using the instrument name should usually be enough.

After you have done that it comes time to write the actual translations.
One-to-one translations are handled in the %hdr hash, with the generic
headers being the keys and the instrument-specific headers being the
values. For many-to-one translations, set up the to_ and from_
methods.

UTDATE, UTSTART, and UTEND be returned as Time::Piece objects when
translating to generic headers, and must be passed as Time::Piece
objects when translating to instrument-specific headers. Keep this
in mind when writing translations for these three.

Examples of translations can be found in the Astro::FITS::HdrTrans::IRCAM
subclass.

Don't forget to return a true value from your subclass by putting "1;"
on the last line!

Where can I get it?
-------------------
The package is available from CPAN <http://www.cpan.org/>.

Installation
------------
Installation is automated using the ExtUtils::MakeMaker library

    % perl Makefile.PL
    % make
    % make test
    % make install

Authors
-------
The module was written by Brad Cavanagh <b.cavanagh@jach.hawaii.edu> of 
the Joint Astronomy Centre (JAC) in Hawaii.

Copyright (C) 2003 Particle Physics and Astronomy Research Council.
All Rights Reserved. This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.

Maintainer
----------
The package is currently maintained by Brad Cavanagh 
<b.cavanagh@jach.hawaii.edu>.

Changes
-------

 v0.01 - initial test release to CPAN

 v0.02 - Change licence in README to be same as Perl.
         Add copyright statement.
         Add requirement on Test::More and Time::Piece to Makefile.PL.