Skip the time-consuming generation of planet models unless one
or more of the required files is missing.
This will cause the planet models to always be exercised by
Travis CI, but most of the time in my own development, they will
be skipped. This is a good compromise now that the code is very stable.
Using moon phase test data, exercised the calculation of
ecliptic longitude of the Sun and Moon at indicated times.
Compared the actual difference in longitude with 90*phase degrees,
where phase is 0 for new moon, 1 for first quarter, 2 for full,
3 for third quarter. The results always agree within 1 arcminute
(just barely).
Added this to the unit test.
Will come back and add unit tests for the phase searcher once
I implement it.
I kept having trouble with Travis CI timing out trying
to download the DE405 ephmeris file from its official ftp site,
so I'm mirroring it on my own GitHub account.
Hopefully this makes the download smoother.
I found some online resources that helped me track down the
formula for the refraction model used in the JPL Horizons
online tool. Now the JavaScript library allows 4 different
refraction options in Astronomy.Horizon():
false : no refraction
'novas' : use the NOVAS C 3.1 algorithm.
'jplhor' : JPL Horizons algorithm, clamped beyond 1 degree below horizon.
'sae' : same as 'jplhor', only without clamping.
Now passes the jplcheck unit test without filtering out objects below the horizon!
Always compile the C code when executing the script './run'.
