NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Sextant mirror silvering
From: George Huxtable
Date: 2006 Nov 8, 13:09 -0000
From: George Huxtable
Date: 2006 Nov 8, 13:09 -0000
Frank wrote in [NavList 1642] Re: Don't do this to a sextant | While I'm thinking of it, sextants usually work without serious problems | even with mirrors that have lost 10 or 20 percent of the silvering. Since the | focus is at infinity, a few blemishes eight inches away don't really cause any | problems. I have an octant from c.1830 that works fine despite missing about | 20 percent of the reflective material on both mirrors. I can imagine a potential problem, in that case, when taking altitudes of stars. There may be an intended star, reflected as normal in the index mirror, which may perhaps be confused with a brighter star, rather overhead and somewhat behind the observer's head, seen through the holes in the silvering. Can that happen, in practice? George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
