NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunar distance accuracy
From: Frank Reed
Date: 2007 Oct 23, 21:39 -0400
From: Frank Reed
Date: 2007 Oct 23, 21:39 -0400
Alex, you wrote: "These are all data I have. I will be very grateful if someone points to any other hard data or research on the subject." You may have missed the article by E.J. White from 1889 that I described on the list almost a year ago --I know you get busy now and then and don't follow the list as closely as you would like. Here's a paragraph from my post back then: "White then details the lunar distance observations he has made in the past three years: forty-two lunars in 1887, 1888, and 1889. He lists the time and measured distance (only approximately, not enough detail to re-work them today) and also lists the error of the resulting longitude in seconds of time. We can convert this to an approximate error in the measured lunar by dividing by 120. That is, an error of 12 seconds in the longitude is approximately equivalent to an error of 0.1 minutes of arc in the measured lunar distance. Calculating from his listed numbers, I find he has a standard deviation in Greenwich time of about 30 seconds which is equivalent to about 0.25 minutes of arc in the lunar distances. If we take his lunars in sets of four and average them (which I consider the best approach with lunars), the results are generally within 0.1 minutes of arc. I would note that these results are very similar to my own experience." The original post is here: http://fer3.com/arc/m2.aspx?y=200611&i=101759 As noted then, I found White's article originally while digging around in Google Books. Since it's short, I've also made it available on the web here: www.HistoricalAtlas.com/lunars/ejwhite. -FER www.HistoricalAtlas.com/lunars --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---