Re: Problems Meeus Apparent Place of a Star in comparison with Astr. Almanac

<Markus.Knapek@xxxxxx> wrote in message
news:1193390672.015563.304370@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I have used the implementation of the Apparent Place of a Star method
from Ephemeritis (Mike McGavin) based on Meeus Astronomical
Algorithms. The implementation works fine for example 22a with an
error much below 1arcsec. So I guess the implementation is fine. But I
have also tried to compare the results with the Astronomical Almanac
(Year book 2006). So I have changed my program from the example for
the target epoch J2006.5 and compared the position of Theta Phersei
with the position given in the Astr. Almanac Bright Stars Table. It
differs by more than 20arcsec, which is quite bad. Below the results
from my program and also the listing of my program (should anybody
have used the implementation by Mike). Has anybody compared the
results obtained from Meeus with the Astr. Almanac? I would thankful
for any help!

The tabulations in AsA Section H are mean place, not apparent place, so
the differences you are seeing are presumably aberration and nutation.
Starting from the AsA figures I get:

02 44 38.8 +49 15 20 J2006.5 mean place (from AsA)
02 44 37.3 +49 15 14 2006 07 03 geocentric apparent apparent place

Patrick Wallace
STFC/RAL/SSTD UK


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