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Re: Celestial Navigation Data from USNO--alternative
From: Paul Hirose
Date: 2019 Nov 29, 14:59 -0800
From: Paul Hirose
Date: 2019 Nov 29, 14:59 -0800
On 2019-11-25 10:32, Bill Ritchie wrote: > Astron gives the Moon Hc as -04° 51.79'. Andres as -04º 51.88'.. Frank's > Lunars Calculator, tweaked to extract the > extra decimal place, gives -04° 51.84' , midway between the two! I suspect the predicted delta T accounts for most of the discrepancies. For the same UT1, each +1 s in delta T decreases Moon hour angle .5″ or .008′. In this case the effect is to increase altitude .007′. In another message Bill Ritchie says, "Astron gives Delta T = 83.139". With that value my altitude matches within .008′. The formulation you adopt for the precession and nutation of Earth's pole affects azimuth and altitude. Minor differences in the Moon ephemerides may be involved, though that should be out of the question if a JPL ephemeris from the last 20 years has been utilized. -4°51.856' DE406 (1997) -4°51.856' DE422 (2009) -4°51.856' DE431 (2013) Hc at 2037-11-24 14:00:00.000 UT1 +1m12.820s delta T -77°00.000' +39°00.000' east lon, north lat IAU 2006 precession, 2000B nutation My delta T comes from a 2016 paper: http://fer3.com/arc/m2.aspx/Delta-T-long-term-formula-Hirose-feb-2018-g41332 http://fer3.com/arc/m2.aspx/Delta-T-long-term-formula-Hirose-feb-2018-g41398
