Improve precision of sidereal time equinox method

This does not affect any tests, but seems worth carrying through as I am otherwise trying to improve precision in Earth rotation.
2020-07-19 06:06:02 -04:00 · 2020-07-19 06:06:02 -04:00 · 0099c353e7
parent 43fdb7bc9d
commit 0099c353e7
1 changed files with 1 additions and 1 deletions
--- a/skyfield/earthlib.py
+++ b/skyfield/earthlib.py
@ -139,7 +139,7 @@ def sidereal_time(t):
    # Precession-in-RA terms in mean sidereal time taken from third
    # reference, eq. (42), with coefficients in arcseconds.

-    t = (t.tdb - T0) / 36525.0
+    t = (t.whole - T0 + t.tdb_fraction) / 36525.0
    st =        ( 0.014506 +
        (((( -    0.0000000368   * t
             -    0.000029956  ) * t