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On 5/5/2023 1:11 AM, I wrote:
> Also you can try the planetary and stellar reduction examples in the
> 2019 Astronomical Almanac:
>
> https://archive.org/details/binder1_202003/page/n183/mode/2up?view=theater

planetary (equinox method)
6 04 36.1041,   +23 23 20.899  Almanac
6 04 36.104013, +23 23 20.8989 Lunar 4.4

planetary (CIO method)
6 03 37.0923,   +23 23 20.899   Almanac
6 03 37.092273, +23 23 20.8989  Lunar 4.4

stellar (equinox method)
14 40 52.3309,   —60 54 21.915  Almanac
14 40 52.330947, -60 54 21.9156 Lunar 4.4

stellar (CIO method)
14 39 54.8308,   —60 54 21.915 Almanac
14 39 54.830827, -60 54 21.9156 Lunar 4.4



> For a
> topocentric example, see this page by Patrick Wallace:
>
> https://syrte.obspm.fr/iauWGnfa/ExPW04.html

fictitious star, az/alt
116.44983979538, 89.79843387822 Wallace ("topocentric")
116.44987559     89.79843384    Lunar 4.4

Azimuths are 1.3" different. But this has little effect because the star
is very near the zenith. The important thing is the angular separation
between the vectors (Wallace vs. Lunar): 0.5 mas.

Most of the discrepancy is probably due to the different precession and
nutation models. Wallace uses IAU 2000 precession (the 1976 model with a
simple correction), 2000A nutation (the current IAU model, which has
1400 terms), and he applies the pole offset corrections (+0.038,-0.118 mas).

Lunar 4.4 uses IAU 2006 precession and the simplified 2000B nutation,
which is accurate to 1 mas from 1950 to 2050. It does not apply a pole
offset correction. Within its limitations it performs well on the
Wallace example.

--
Paul Hirose
sofajpl.com

   

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