NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Latitude by Lunar Distance
From: Dave Walden
Date: 2006 Oct 14, 04:14 -0700
From: Dave Walden
Date: 2006 Oct 14, 04:14 -0700
I have indeed reproduced Frank's results using the data and procedures given in his postings. I have been somewhat surprised at the vehemence with which people say his method can't/won't/shouldn't possibly work. Particularly from those who seem to be saying not enough information has been given to know what he has done. The lines of position are about five miles wide for this case. The intersecting lines give a parallelogram (the "cocked hat" for this method) with an extreme corner to corner distance of something over 5 miles depending on the angle of intersection of the lines. On the "cones", it seems to me, the axis of the cone must be line between the star and the center of the moon. As shown in the figures, the axis doesn't necessarily intersect the surface of the earth. Perhaps the implied iteration to find the desired latitude on the 70 deg West longitude line is confusing to others. Another approach, although less accurate, is to find the cleared distance at 38N and 39N and interpolate to the desired value. This would require only 4 calculations initially for each star and a couple more to refine the answer. All and all, an interesting discussion. I'd never done any type of lunar before. (Not easy for us bubble sextant users to make this measurement, on the other hand, we always have a "horizon"!) Not as complicated or hard as I'd thought. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---