| 1 | PAL - Positional Astronomy Library
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| 2 | ==================================
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| 3 |
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| 4 | [](http://dx.doi.org/10.5281/zenodo.17212)
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| 5 |
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| 6 | The PAL library is a partial re-implementation of Pat Wallace's popular SLALIB
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| 7 | library written in C using a Gnu GPL license and layered on top of the IAU's
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| 8 | SOFA library (or the BSD-licensed ERFA) where appropriate.
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| 9 | PAL attempts to stick to the SLA C API where
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| 10 | possible although `palObs()` has a more C-like API than the equivalent
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| 11 | `slaObs()` function. In most cases it is enough to simply change the function
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| 12 | prefix of a routine in order to link against PAL rather than SLALIB. Routines
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| 13 | calling SOFA use modern nutation and precession models so will return slightly
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| 14 | different answers than native SLALIB. PAL functions not available in SOFA were
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| 15 | ported from the Fortran version of SLALIB that ships as part of the Starlink
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| 16 | software and uses a GPL licence.
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| 17 |
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| 18 | See `pal.news` for release notes.
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| 19 |
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| 20 | Building
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| 21 | --------
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| 22 |
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| 23 | A simple `configure` script is provided:
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| 24 |
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| 25 | ./configure --prefix=/usr/local --without-starlink
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| 26 | make
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| 27 | make install
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| 28 |
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| 29 | The tests can be run using `make check`. Use `--prefix` to specify an install location.
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| 30 | Given the history of the source code as a Starlink library the default will be `/star`.
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| 31 |
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| 32 | `--without-starlink` forces the configure script to forget about any Starlink
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| 33 | configurations. This is the safe option if you run into problems when using
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| 34 | a simple `--prefix` for building outside of Starlink. The configure script
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| 35 | will assume Starlink is not being used by looking to see if
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| 36 | `STARCONF_DEFAULT_PREFIX` environment variable is set. You may run into problems if
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| 37 | `STARCONF_DEFAULT_PREFIX` is set but you use `--without-starlink`.
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| 38 |
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| 39 | Requirements
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| 40 | ------------
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| 41 |
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| 42 | Requires that either the SOFA C library or the ERFA library variant
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| 43 | (which has a more permissive license than SOFA) be installed. The
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| 44 | `configure` script will abort if neither SOFA nor ERFA can be
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| 45 | found. SOFA can be obtained either from <http://www.iausofa.org> or
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| 46 | from an unofficial github repository (with a configure script) at
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| 47 | <https://github.com/Starlink/sofa/downloads>. ERFA can be downloaded
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| 48 | from <https://github.com/liberfa/erfa>.
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| 49 |
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| 50 | Missing Functions
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| 51 | -----------------
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| 52 |
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| 53 | Not all SLALIB functions have been added. New routines are added to PAL as demand arises.
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| 54 |
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| 55 |
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| 56 | Language Bindings
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| 57 | -----------------
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| 58 |
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| 59 | A Perl binding of PAL is available (<https://github.com/timj/perl-Astro-PAL>) named `Astro::PAL`
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| 60 | and is available from CPAN at <https://metacpan.org/module/Astro::PAL>. This is a standalone
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| 61 | distribution that comes with its own copies of PAL and SOFA and so can be installed directly
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| 62 | from the `cpan` shell.
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| 63 |
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| 64 | A Python binding of PAL is available (<https://github.com/Starlink/palpy>). This is a standalone
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| 65 | distribution that comes with its own copies of PAL and SOFA.
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| 66 |
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| 67 | The Starlink AST (<http://www.starlink.ac.uk/ast>) library now uses PAL and can be built
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| 68 | either with a private PAL or with an external PAL.
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| 69 |
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| 70 | Documentation
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| 71 | -------------
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| 72 |
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| 73 | The description paper for PAL is: ["_PAL: A Positional Astronomy Library_"](http://adsabs.harvard.edu/abs/2013ASPC..475..307J),
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| 74 | Jenness, T. & Berry, D. S., in _Astronomical Data Anaysis Software and Systems XXII_,
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| 75 | Friedel, D. N. (ed), ASP Conf. Ser. **475**, p307.
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| 76 |
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