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On 2015-11-05 0:12, I wrote:
> I checked lunar distance at
> the given position and times with my Lunar3 program. Assuming the times
> are UT1, at immersion [21:49:49] I have lunar distance -0.0002° to Aldebaran. At
> emersion [22:48:24] it's +0.0003°.

After recalculating with a more accurate semidiameter, those lunar
distances decreased by .0001°, to -.0003° and +.0002°.

Since Bob Crawley mentioned the effect of Earth's oblateness, I tried a
spherical Earth with the same latitude, longitude, height (zero), and
equatorial radius. The new lunar distances were +.0027° and .0000°. The
last is not a typo. Apparently the geometry is such that the difference
between a sphere and an ellipsoid is insignificant at emersion time.

I also calculated the coordinates (on the GRS80 ellipsoid) that put the
observer at the same point I got with a spherical Earth. The actual
coordinates of Orwell Observatory are on the upper line.

N52 00.6 E001 13.8      0 m
N52 11.8 E001 13.8 +13300 m

   

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