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Re: 18 june 2013 lunar distance
From: Paul Hirose
Date: 2013 Jul 03, 12:53 -0700
From: Paul Hirose
Date: 2013 Jul 03, 12:53 -0700
Antoine Couëtte wrote: > In RE# 1, for (apparently) exactly the same date and time "[2013-06-18 0330 UT1, 67.1178 delta T, DE406 ephemeris, Hipparcos second reduction]" I can read that you published the Moon and Altair coordinates as follows : > > QUOTE > > From Lunar3 I get Moon coordinates > > -2.44969548e-003 -5.24187596e-004 -3.58294080e-004 au, or > 192° 04′ 40.973″ -08° 08′ 21.886″ > > and Altair coordinates > 4.59325899e-001 -8.74784757e-001 1.54179599e-001 au, or > 297° 42′ 09.913″ +08° 52′ 09.188″ > > UNQUOTE > > I can see that both sets of results are quite different. Thank you for the reply, Kermit. The part you did not quote explains the mystery: "And to eliminate any question about the precession / nutation model, I wonder if Dave can put the coordinates in the GCRS. From Lunar3 I get Moon coordinates..." So the coordinates above are in the GCRS, not the true equator / equinox system. For the latter, computed with the IAU 2006 / 2000A precession nutation model, Lunar3 says, 12h49m01.4774s -8°12′48.749″ Moon 19h51m28.2889s +8°54′23.396″ Altair As a check, the separation angle between those coordinates should be the same as the angle computed from the GCRS coordinates. I get 106 34 28.454, only 1 mas greater. From your coordinates I compute 106 34 29.454. --