NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: EBBCO/filters
From: Michael Daly
Date: 2007 Nov 21, 02:36 -0500
From: Michael Daly
Date: 2007 Nov 21, 02:36 -0500
Greg R. wrote: > Do those have the right filters for the damaging rays of the sun (UV, > etc.)? I'd be more inclined to just replace the sextant itself rather > than take a chance on permanent and irreparable eye damage. Welding glass is just as safe as eclipse (aluminized mylar) filters or steel (or steel/nickel/whatever alloys) coated glass filters used in astronomy. The trick is getting the right welding glass. A single layer has to be quite dark - #14 for direct observation of the sun. You can use multiple filters of lower density and stack them (most sextants have three or four on the index mirror path and three on the horizon mirror), but I'm not sure of the way to choose the shade numbers (SN) to get the right values. ISTR that the SN are simply additive (e.g. two 7s = one 14), but I can't confirm, so do your homework before taking this route. Mike --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
