NathanKell/RealSolarSystem — pull request #5 by eggrobin (2014-03-29 19:38:18+00:00)
Title: Equatorial B1950.0 coordinates

My branch's name is misleading :-p.
To quote my comments:
```c#
// Form: Epoch is the time in seconds until the epoch of orbital elements.
// We use B1950.0 == 1949-12-31 22:09:18.216 Temps Atomique International.
// The game starts at 1950-01-01 00:00:00.0000 Temps Atomique International.
// In other words, the year 1950 begins in Greenwich roughly when the game
// starts (We do *not* use UTC because leap seconds are discontinuous, and UTC
// is not defined in 1950; UT1 is a right mess).
// The time to epoch was computed as -(24*3600 - 22*3600 - 9*60 - 18.216).

// The orbital elements are computed using the Jet Propulsion Laboratory
// HORIZONS system (http://ssd.jpl.nasa.gov/horizons.cgi) using the following
// settings in order to get correct axial tilt for Earth at epoch:
// Start time : A.D. 1949-Dec-31 22:09:50.4000 CT [JD2433282.4235]
// Reference frame : FK4/B1950.0
// Output type : GEOMETRIC osculating elements
// Coordinate systm: Earth Mean Equator and Equinox of Reference Epoch
// We use the primary's centre as our centre, this results in accurate
// positions at epoch. To quote HORIZONS,
// Reference epoch: B1950.0
// xy-plane: plane of the Earth's mean equator at the reference epoch
// x-axis : out along ascending node of instantaneous plane of the Earth's
// orbit and the Earth's mean equator at the reference epoch
// z-axis : along the Earth mean north pole at the reference epoch
// We do not set the periods because nothing good can come out of
// inconsistent orbital elements.

// Inital rotation computed from http://ephemeris.com/ephemeris.php.
// at a longitude of 0.
// The date was set to 1950-01-01 00:00:26 UTC, in order to match the
// JD (2433282.500301) as close as possible to the beginning of the game,
// 1950-01-01 00:00:00 Temps Atomique International == JD2433282.5003725.
// The result from the ephemeride was 06:40:44, converted to 100.1833 deg.
// We add 90 degrees because KSP is being silly.
// NOTE THAT INITAL ROTATION IS NOT AFFECTED BY THE EPOCH SETTING.
```