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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunar trouble, need help
From: Frank Reed
Date: 2008 Jun 15, 13:16 -0400
From: Frank Reed
Date: 2008 Jun 15, 13:16 -0400
Jim, you wrote: "I took the time to interpolate between your first and second Sun and Moon altitudes. I then used the online calculator using interpolated values for the altitudes and the time of each LD observation to determine the error in the observed lunar distances which I found to be: 3) 1.4 4) 1.0 5) 1.0 6) 1.2 7) 0.9" But you got these values, Jim, by ASSUMING that these were Far Limb sights, right? The problem is that Jeremy took Near Limb lunar distances (and when you're shooting Sun-Moon lunars, that's always the case unless you're trying something rather exotic). Cleared as Near Limb lunars, the error is around half a degree. This implies some big "blunder" -- it couldn't be an observational error. One possibility is recording the time incorrectly on all the sights. It's surprisingly easy to do this: you write down 7 hours when the watch says 6 hours because you're thinking about something you have to do at 7 hours. I experimented a little with Jeremy's sights and could not find anything like this. The Sun and Moon altitudes are consistent with the DR location and the UT as recorded. Can anyone think of some other error in writing down the sights that would lead to an error in all the lunar distances of just over half a degree? Jim, something you might get a kick out of: You cleared Jeremy's sights by interpolating for the exact altitude of the Moon. Try it again with the Moon's altitude shifted up or down by one whole degree. How much does it influence the cleared lunar? Lunars near 90 degrees are special this way --large errors in the Moon's altitude make little difference. -FER PS: Finally "de-compressed" I should be posting extensively in the next couple of days. --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---