NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Precision of lunars
From: Alexandre Eremenko
Date: 2007 Apr 24, 13:17 -0700
From: Alexandre Eremenko
Date: 2007 Apr 24, 13:17 -0700
Dear Frank, > You're still not getting very good results, and you're content to believe, In fact I thought that the results I recently posted are "very good". I would be very interested in seeing any results which you use as comparison pool. Your own of of those "novices". Meanwhile I post my recent results, so that together with the previous recently posted we have a complete set of 1 month observations. I stress that this is a COMPLETE set, including good and bad observations. If I wanted to choose a "typical one", by any criterion (average, median, etc.) this typical one will have error less than 0.2. There are all Lunars with SNO-T and 6x scope. April 20 Venus at 11d. Errors: 0.1, 0.1, -0.2, 0.15. April 20 Saturn at 57d. Errors: -0.1, 0.1, 0.0 April 21 Venus at 21d. Errors: -0.3, -0.2, 0.1, -0.2, -0.1 April 21 Pollux at 19d. Errors: 0.0, 0.2, 0.2, -0.1, 0.2 April 21 Spica at 110d. Errors: 0.5, 0.5, 0.5 Same again, AFTER reduction of the previous 3: April 21, Spica at 110d. Errors 0.2, 0.0. (Explanation: I DID NOT preset the sextant, I just found out that I was overshooting by 0.5. After that I adjusted by eye. The problem was that Moon was too bright in comparison with Spica at that time. And using 2 light filters did not help. So I really did not see Spica at the moment of tangency, being overshined by the Moon). So I took another star which looked the same as Spica in that conditions: April 21, Regulus at 56d. Errors 0.5. April 23, Venus at 46d: Errors: 0.1, 0.2, 0.2,-0.3, 0.1. > So we can certainly > "see" angular shifts smaller than 0.5 minutes of arc. Sometimes we can sometimes not. (See the examples above with Regulus and Spica. They were faint on the background of city lights. Moon in another direction was too bright. There were no proper filters to "extinguish the Moon". Two light filters were not enough, and through the other two "sun filters" the Moon was not visible. > What's your latest > theory on the reasons you've been unable to do as well as you would like with > your observations? I have no theory, except that I gained some experience. Experience of a very special kind: just how should a star and Moon look when they really touch. And this depends on the star, weather conditions and the scope used, and many other factors. That's why I call this experience. This cannot be explained or taught in one hour. That's why I am so curious to see the statistics of novices that can do better with an unfamiliar sextant. Alex. > -FER > 42.0N 87.7W, or 41.4N 72.1W.www.HistoricalAtlas.com/lunars > > ************************************** See what's free athttp://www.aol.com. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---