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Re: Lunar4.4. vs Frank's online calculator
From: Paul Hirose
Date: 2023 May 5, 13:48 -0700

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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