NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Vernier sextant
From: Alexandre Eremenko
Date: 2007 Mar 05, 16:07 -0800
From: Alexandre Eremenko
Date: 2007 Mar 05, 16:07 -0800
Bill, On Mar 3, 1:36 am, Billwrote: > I'm still waiting on more bubble sextant results. I have plenty. And I am ready to share them with you. I just do not post them on the list, because, apparently there is no interest in the raw numbers in this list. One of the ususual results I have is a daylight observation of Venus. I mean before the sunset. Since my childhood I know (theoretically) that you can see bright stars in daylight. If you know precisely where to look. If you do not know where to look, you can miss even a very well visible object:-) This I know by experience as a anti-aircraft artillery officer:-) A low flying plane comes, you hear the sound (which comes from a deceptive direction if the airplane is fast enough). You lookouth. at the sky and you see nothing. Until someone spots it, points at it, and then you suddenly see it. Same with stars. Very bright stars are well visible in daylight. The star navigation authorities (Chichester and Lecky) recommend the following. You pre-compute the time and alt of meridian passage. You preset this alt on your sextant. Then, at a pre-computed time you point it North or S. And you see the star! Instead, I pre-computed the Sun-Venus distance and pointed my sextant at the Sun, rocking it and trying to find Venus. I failed 1 hour before sunset but succeeded twice 1/2 hour before the sunset. I could even measure the Sun-Venus distance with my sextant. Returning to my vernier sextant. So far my Lunars are bad. I mean VERY bad. Several minutes off. Only now I really understand the advantages of the modern sextants:-) (Large FILTERS (I do not care about large mirrors!), good optics, and easy reading scale). And light weight for alluminium ones:-) But I continue my experiments. Alex. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---