NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextants with Polarizing filters
From: Frank Reed CT
Date: 2006 Jan 30, 02:25 EST
From: Frank Reed CT
Date: 2006 Jan 30, 02:25 EST
Joel Jacobs, you wrote: "There were limited quantities of Navy MK II sextants made with polarizing filters for use in WW II. Every once in a while one will surface." That's what got me wondering. I've been playing with one of those recently, and it seems like an effective design. Also, in the 1962 Bowditch, the first sextant pictured in article 1503 "Micrometer Drum Sextant" is a Navy Mk II with polarizing filters. The text in this edition reads "Older sextants have two sets of shade glasses, as shown in figure 1504. Many modern sextants are fitted with a single Polaroid filter of variable darkness in place of each set of shade glasses, as shown in figure 1503a." Of course, it's not really a "single" Polaroid. It's a pair mounted in a single unit --one with fixed orientation and the other rotatable. And you wrote: " In general, they never really caught on in the navy or out." Any speculation on why not? They seem convenient to me. If I had my choice, I think I would prefer one standard shade of medium darkness and one polarizing unit for the greatest possible range of brightness reduction, in both locations where sets of shades are usually found on sextants. And you wrote: "Capt. Sorreson of Coast and Simex fame was a proponent, and you see many of the Simex brand, a private label, with them." I think I have a cousin of a Simex sextant. It's marked "International Nautical", and it's a Tamaya-alike in appearance. It's not a Simex by another name, is it? Despite its rather "generic" branding, it has proven to be a remarkably accurate instrument by every test I've subjected it to. It has nice, large polarizing units instead of standard shades. The rotating parts were stuck rock solid after years in the box (this instrument was apparently never used), and I half suspect that a previous owner or two did not realize that the shades were polarizers at all. There's a picture of one of these here: http://www.nauticalantiquesandgifts.com/catalog/item/2418044/1886664.htm (mine was a lot cheaper) Joel, you have apparently written on this topic before on the list. I've found replies to your messages on 'Tamaya and Simex' and all that in the list archives, but for some reason I can't find the original message(s). So I would appreciate hearing what you know about this. -FER 42.0N 87.7W, or 41.4N 72.1W. www.HistoricalAtlas.com/lunars