NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Moon - Antares
From: Frank Reed
Date: 2009 Jan 24, 18:11 -0800
From: Frank Reed
Date: 2009 Jan 24, 18:11 -0800
"If knew roughly where I was and had some instrument with horizontal and vertical cross hairs, I could mark when the star had the same altitude or azimuth as a limb of the moon. My almanac or computational tool could then be used to determine the UT for that event." Yes, and thinking about it further, as long as the ecliptic is relatively vertical (within let's +/-30 degrees) at the time of the observation, it ought to give a fairly good value for GMT. The usual objection to using lunar altitudes for longitude is that observations of altitudes are much less accurate than observations of lunar distances, by a factor of five or even ten. But if you measure the altitude of a star *and* the Moon and wait for them to be nearly identical, then most sources of error are cancelled out. On land you could even dispense with a sextant and do this by lining the two objects up along the roof line of a nearby building, assuming it's level. With a sextant, you could take a series of sights over several minutes alternating between Moon and star. Then graph them to find where they cross. I suppose if you had a vertical reference of some sort, like the side of a building, you could do the same thing with azimuth... -FER --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---