NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Bris Confusion
From: Alexandre Eremenko
Date: 2015 Jun 25, 17:59 +0000
From: Alexandre Eremenko
Date: 2015 Jun 25, 17:59 +0000
You can find very fine pictures of the original Bris here, together with some theory and some observations. http://www.math.purdue.edu/~eremenko/Navigation/Sextants/Bris/ The Sun ray enters the dark glass. Usually I see 4 bright suns and 6-7 dim ones. All glass surfaces must be very clean. Once I carried it on a rope hanging on my neck under the shirt, and the sextant became unusable because the surfaces were covered by sweat vapors:-) Cleaning the inner surfaces in non-trivial. I purchased it from Cassens Plath 10 years ago and they told me that this was the last one they had. Alex. ________________________________________ From: NavList@fer3.com [NavList@fer3.com] on behalf of Marty Lyons [NoReply_MartyLyons@fer3.com] Sent: Thursday, June 25, 2015 12:01 PM To: eremenko@math.purdue.edu Subject: [NavList] Bris Confusion I read the archived articles on the Bris, somewhat confusing. Pretty fascinating though, so I made one. I used three glass welding shields, two clear and one #5 shaded, spaced at slightly different angles. My questions are: 1. Is the light supposed to enter the Bris from the top, in the spaces between the glass or through the back of the shade? 2. I see what I think are a bunch of reflections. I will say, 1 bright, 2 less bright, 4 dimmer yet and on very dim. Is that correct? 3. So to understand the principle, I sight the horizon and wait until one of the images comes down or up to the horizon and time it? 4. I then work the sight backwards, using either manual methods or software solutions? [PLAIN TEXT VERSION OF MESSAGE AUTO-GENERATED. ORIGINAL MAY INCLUDE MORE CONTENT] ---------------------------------------------------------------- NavList message boards and member settings: www.fer3.com/NavList Members may optionally receive posts by email. To cancel email delivery, send a message to NoMail[at]fer3.com ---------------------------------------------------------------- Attached File: http://fer3.com/arc/imgx/IMG_2366.JPG Attached File: http://fer3.com/arc/imgx/IMG_2367.JPG : http://fer3.com/arc/m2.aspx/Bris-Confusion-MartyLyons-jun-2015-g31891
