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On 2014-11-23 20:26, Paul Hirose wrote:
> The western U.S. has a chance to see a lunar occultation on Nov. 27 at
> about 0340 UT (evening of Wednesday the 26th local time), when beta
> Capricorni disappears behind the dark limb of the crescent Moon.

I observed the occultation .7 second early compared to the prediction
from my program. The lunar distance rate was .44″ per second of time, so
the error was equivalent to about .3 second of arc. That's a
satisfactory result, but an occultation doesn't test the program's
refraction correction to lunar distance. (I have tested that part by
calculation.) And, as good old George Huxtable liked to remind us, a
single result doesn't prove much.

The program's option to apply a simple correction for the discrepancy
between the Moon's center of mass and center of figure helped. This
correction (explained in any edition of The Astronomical Almanac) has
long been used in eclipse predictions. If the option had been turned
off, the prediction would have had an additional .6 second error in time.

Genuine occultation programs probably account for the non-circular shape
of the Moon's limb. I have never gotten that elaborate, and probably
never will!

   

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