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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Working a lunar
From: Paul Hirose
Date: 2009 Aug 02, 15:13 -0700
From: Paul Hirose
Date: 2009 Aug 02, 15:13 -0700
Antoine wrote: > So, my results would not be that bad ... Your results are only 1 second different from my program. But it recommends the upper limb of the Moon, because the light is coming from almost directly above (position angle = 350°). Of course, if the "observation" was calculated, this doesn't matter. Even if it was really observed, I don't think there is much error because the Moon is nearly full (phase angle = 4°), and the cleared lunar distance is not very sensitive to altitude. My corrected time is 2001-04-08 at 03:21:10.5 UT1 (03:22:14.5 Terrestrial Time). Position fix from the altitude observations is N44°50.48' W011°01.08'. I checked the solution by entering the Terrestrial Time, latitude, and longitude W11°17'07.2" into the USNO MICA 2.0 program. Longitude equals my solution, moved west by delta T (64 seconds) converted to arc (= 64 * 15 * 1.002738 arc seconds). With these inputs, the outputs from MICA should match the observations. (MICA does not compute refraction, so I used my program's values.) 31.4506 Moon altitude - .2718 semidiameter + .0263 refraction --------- 31.2051 lower limb (calculated) 31.2050 lower limb (observed) 17.7536 Mars center + .0497 refraction --------- 17.8033 refracted center (calculated) 17.8033 refracted center (observed) 64.9266 refracted separation angle + .2718 Moon semidiameter -------- 65.1984 lunar distance (calculated) 65.1983 lunar distance (observed) The check is good. -- --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
