NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Simex Mariner Polarized Shades...How Well Do They Work/10X Inverting Scope
From: Frank Reed
Date: 2009 Jan 14, 19:20 -0800
From: Frank Reed
Date: 2009 Jan 14, 19:20 -0800
You wrote: "Speaking as a photographer, there's a lot to be said for a variable polarizing filter. OTOH, most good sextants have filters that are effective at dimming glare along the horizon, below the sun. I wouldn't go out of my way for just this feature." Right. No reason to go out of one's way for this, but they do work. Incidentally, some sextants included these polarizing shades as far back as the Second World War. You mentioned horizon glare... While some polarizing filters are used to eliminate the reflected light off the water (which tends to be polarized in a way that can be easily filtered), that's not what's going on here. These filters are crossed polarizers. The idea is that you can vary the angle at which they cross, by turning one of the pair, and reduce the total brightness of the light passed through. I should mention that some of the sextants that come up on ebay have been in storage for as much as twenty years. I bought one recently that appeared to be absolutely brand new, with the original packing materials in the case, that was manufactured in 1976. That's a great thing EXCEPT that sometimes the lubricants have dried or otherwise changed where they're exposed to air, and parts may be "frozen". In particular, the housings that hold the rotating polarizer in sextants may seize up. A little gentle prying with a very thing screwdriver blade got mine moving again. -FER --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---