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post #1 of 10 Old 04-29-2008 Thread Starter
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US Navy Mark II Sextant

I recently purchased a Navy Mark II sextant (David White - 1941) both for its antique value and hopefully as a means of maintaining my proficiency in using a sextant. I have a couple of questions regarding the adjustment and use of this intstrument and would appreciate some advice from someone (perhaps a Navy vet) who is familiar with its features.

First, the square-headed socket (looks a little like a thumbscrew) used to adjust the horizon glass was not included in the case. What else could be used in its place, or can it be replaced from some commercial source?

Secondly, this sextant is fitted with the polarized filters. Do they tend to lighten or fade over time? Do they provide enough eye protection to use for sun sights?

Thank you for any assistance or help you may be able to give.
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post #2 of 10 Old 04-29-2008
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Check with Robert E. White Instrutments in Boston. This is where I bought my sextant. They may have the parts you need.
As old as your sextant and those filters haven't faded yet... I don't think that they ever will. But you can ask the above about it.
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post #3 of 10 Old 04-29-2008
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You might see a clockmaker or repairman for the square head wrench-it doesn't have to be very strong and most wind-up clocks use a square head key.

The filters should be fine if the sextant has been kept in it's case. They're really not out in the sun that much that they should have faded. Be aware that not all the filters are dark. The horizon shades have to deal with fog and glare which call for just a slight shading.

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post #4 of 10 Old 04-30-2008
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I also recently purchased a 1941 vintage D. White Navy MKII. Fortunately, the hex wrench and other tools were included. The wrench is also used to adjust/tighten several other fasteners on the instrument, so it's a necessary tool to have.

My version has the colored leaf filters; as I understand it, later versions built by D. White, Bendix and Ajax were adapted with polarizers. The green filter for my horizon glass is cracked, and I'm finding out how difficult it is to locate parts for these old MKIIs - none of the leading repair facilities, including Robert White have them. If anybody has any leads, please let me know.

Bauer's 'Sextant Handbook is an excellent book.' Some good tips on setup and maintenance. The author tends to favor newer instruments with larger mirrors, but it seems to me a properly adjusted MKII can do the job - though I've never done a sight in heavy weather.

Anyway, enjoy the sextant, and hopefully you'll find the right wrench.

Capt Dan G>
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post #5 of 10 Old 05-01-2008 Thread Starter
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I've been following these sextants on e-Bay for some time and have seen several listed which were missing parts, primarily the scopes. Right now there is a David White Mk II offered that has no filters or case.

I've considered bidding on one of these incomplete sextants just for the spare parts, but unfortunately, they often sell for unreasonably high prices. I would assume many buyers want them just for nautical decoration.
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post #6 of 10 Old 05-01-2008
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Quote:
Originally Posted by CaptDanG View Post

My version has the colored leaf filters; as I understand it, later versions built by D. White, Bendix and Ajax were adapted with polarizers. The green filter for my horizon glass is cracked, and I'm finding out how difficult it is to locate parts for these old MKIIs - none of the leading repair facilities, including Robert White have them. If anybody has any leads, please let me know.
You may have some luck with a photography store. If you have the templates from one of the others - they can usually sell you a filter large enough to be cut down with a dremel or other glass cutting tool. Probably a bit of a hack but ...Another option is your friendly eyeglass shop - they sell polarizing filters all the time and usually have to cut them to fit various frame sizes and designs...

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post #7 of 10 Old 05-01-2008
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Quote:
Originally Posted by wrightg7 View Post
I've been following these sextants on e-Bay for some time and have seen several listed which were missing parts, primarily the scopes. Right now there is a David White Mk II offered that has no filters or case.

I've considered bidding on one of these incomplete sextants just for the spare parts, but unfortunately, they often sell for unreasonably high prices. I would assume many buyers want them just for nautical decoration.
I think a 'fair' price for a MKII in serviceable condition, with all accessories and case intact would be in the neighborhood of <>$200-250. I've seen them at retailers for twice that, however. I got lucky and found one owned by a sailor who took care of it, save for the cracked filter, and I paid $175.00 which I think is a good price.

But I think you're right; many eBay buyers are looking for decoration, though I'd advise 'em to just get a cheap Bombay/brass gizmo for $39.00 and call it a day.

Capt Dan G>
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post #8 of 10 Old 05-01-2008
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Originally Posted by artbyjody View Post
You may have some luck with a photography store. If you have the templates from one of the others - they can usually sell you a filter large enough to be cut down with a dremel or other glass cutting tool. Probably a bit of a hack but ...Another option is your friendly eyeglass shop - they sell polarizing filters all the time and usually have to cut them to fit various frame sizes and designs...
Thanks for that tip. It would seem if I could get ahold of a photo filter of proper thickness and have it cut to size, I could burnish it into the filter ring - or have it done by an optical guy, perhaps at Captains Nautical here in sunny Seattle.

Though I was tempted to spend upwards of $500 for a more modern instrument, this ol' MKII still has plenty of 'mojo' for my purposes.

Capt Dan G>
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I would also suggest Robt. White & Co. for spare parts and repairs. They are a very professional firm and will do complete restorations. They answer phone calls--and return them. And while you can certainly DIY for less, they may be very competitive considering that they'll do it all, professionally, and they are intimately familiar with the instruments.
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post #10 of 10 Old 05-23-2008
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Update:

Captain's Nautical in Seattle found a complete, proper replacement for the broken shade - in the right color and original ring housing. They also replaced my horizon mirror with the spare that came with the sextant, and performed an overall adjustment.

2 thumbs up for Captains! Another happy camper.

Capt Dan G>
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