NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Geometry of SNO-T
From: George Huxtable
Date: 2004 Oct 14, 13:13 +0100
From: George Huxtable
Date: 2004 Oct 14, 13:13 +0100
Bill wrote- >I had posted a question a while back, and have received no response. Since >Alex seems to have a good grasp of this now, I will ask him and others to >address it. > >"If the front-silvered mirror is no longer on the axis of the rotation, will >this affect the sextant's performance?" > >I admit my ignorance. > >What I think I know is that if I scribed a line on the index mirror at it's >axis of rotation, and the plane of that mirror was on the axis, that line >would appear at the same elevation in the horizon mirror as I moved the >arm. > >I also think that if the plane of the index mirror moved off the axis, that >line would move vertically as I moved the arm. > >From the reference point of the angles of the index and horizon mirror, no >problem, that relationship will remain the same. > >From the reference point of reflection, so what if the area of the mirror >reflecting or the body changes, Angle in, angle out. > >This is as far as my skill sets get me. >Bill ================= Bill, you got a response, but presumably you missed it. True, it was buried rather deep within a message. It was sent by me at 12:07 on 13/10/04 (GMT + 1:00), threadname "perpendicularity" and read- "As far as actual measurement of celestial angles is concerned, I don't think the precise "fore-and aft positioning of the plane of the index mirror matters a damn, so makers may "perhaps not take that positioning very seriously. George. ================================================================ contact George Huxtable by email at george@huxtable.u-net.com, by phone at 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ================================================================