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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Basics of computing sunrise/sunset
From: Thomas Kleemann
Date: 2009 Jun 19, 23:17 +0200
From: Thomas Kleemann
Date: 2009 Jun 19, 23:17 +0200
Brad Morris schrieb: > > I use a sextant from about 1920. > Should I be worried about the filtering qualities of my shade glasses? > Probably not, in the twenties standards about eye protection were well established (e.g. for iron workers) > Would there be a way to check to see if my shade glasses are up to the mark? > A first qualitative guess (not quantitative tough): If you own some self tinting sunglasses (heliomatic, solarchrome or whatever trademark), you could direct a filtered sunbeam through your sextant at them sitting in the shadow. Compare the grade of tinting against an unfiltered beam. Be aware this method covers mainly UV and natural light, since that is what phototrophic glass reacts on. Exposure to IR can cause eye damage too. HTH, Thomas. --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
