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Old 19-03-2009, 12:11   #76
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Silvering the mirrors may be an expensive proposition. My old Tamiya needs the mirrors silvered. I enquired at a chart and instrument store in Seattle and was quoted a couple of hunder dollars. Seemed exorbitant so I didn't have it done. Haven't got around to finding another possible source. If you find one, let me know.

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Old 19-03-2009, 14:16   #77
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Congratulations on the deal! All is not lost regarding the mirror.

First, you can look into making a replacement yourself. See this article by Bill Morris for information on how to do it. See, too, Morris' examination of how flat glass is - DIY mirrors are a very real possibility.

Failing that, two US companies come to mind as possible resources:
Robert E White Instruments: Robert White
Celestaire: Celestaire - Navigation Equipment

I'm sure there are any number of other possible sources, but this should be a good start.
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Old 19-03-2009, 17:42   #78
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FWIW Roverhi,

From (somewhat fallible) memory, there is a section on re-silvering mirrors in Bowditch. I further recall that said Bowditch is available on line from US Gov pubs.

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Old 19-03-2009, 18:08   #79
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Unfortunately, the 2002 / 2004 (PDF edition of the 2002 ed.) Bowditch says
Quote:
Originally Posted by Bowditch
If the mirrors need re-silvering, take the sextant to an instrument shop.
I'll look in older editions I have but I suspect Bowditch isn't the best bet. I referred Skookum to Bill Morris' web site which has a very good blog entry on replacing mirrors. Long story short, conventional float glass mirrors, cut to shape and painted on the back, will work surprisingly well. See, too, Morris' comments on the flatness of mirrors.

Finding Bowditch on-line has become a little more complicated as it requires drilling down through the NGA (National Geospatial-Intellegence Agency - ex-NIMA) web site to the Publications page and selecting American Practical Navigator, which comes in section.

This link (click here) may or may not work for you.
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Old 19-03-2009, 22:29   #80
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Skookum:

I seem to recall seeing an article dealing with re-silvering, cannot at the moment remember where, however you might try google.com . I will dig around and see if I can find it. You also might try Robert E.White Instruments (www.robertwhite.com). Good luck.

Just "googled" the subject, and found an article in Proceedings of The Naval Institute. Have a look there
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Old 20-03-2009, 05:21   #81
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In addition to the link RBEmerson gave
< Maritime Safety Information >*
where you'll also find the Atlas of Pilot Charts & more

Bowditch is also available on-line, here:
Bowditch Online

* www . nga.mil/portal/site/maritime/?epi_menuItemID=c56aa099e2bff9525b2a7fbd3227a759&e pi_menuID=35ad5b8aabcefa1a0fc133443927a759&epi_bas eMenuID=e106a3b5e50edce1fec24fd73927a759
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Old 20-03-2009, 09:42   #82
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Thank you all of you for your advice. I'm going to visit a local mirror and glass cutter today the see if they can cut a circular mirror for me. I'll try grinding the edges and removing the silvering myself. Failing that, I'll call White's.

Cheers.
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Old 20-03-2009, 21:39   #83
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Quote:
Originally Posted by GordMay View Post
Bowditch is also available on-line, here:
Bowditch Online
That's the 1995 edition. Great because it's online, though.

I have some pdfs on my website for download here: Navigation
  • 2002 Bowditch pdf (40 mb)
  • 2002 Armchair Clestial Navigator (1 mb)
Note, if the downloads start using too much of my quota, I may remove them temporarily.

-dan
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Old 21-03-2009, 07:04   #84
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There's much to be said for on-line editions of Bowditch - they're searchable, for example. OTOH, earlier editions contain useful material that didn't make the cut in the transition from two volumes to one, and again in later one volume editions. And relatively recent two volume editions were slimmed down over time. Some of this is admittedly esoterica but the changes with time make it worth bearing in mind when finding an edition for sale at an attractive price.

Bottom line: there is real value in older editions.
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Old 21-03-2009, 09:18   #85
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So I spoke with Ridge at White's instruments regarding my badly corroded horizon mirror. He said the only part of sextant restoration that White's doesn't deal with in house is the re-silvering of mirrors. Not to worry however since he directed me to Les at Texas Nautical Repair in Huston. This fine chap told me he might be able to re-silver my mirror providing the old coating had not oxidized too severely and become permanently bonded to the glass. He would have replaced the mirror but he had no round optical flats in the size necessary. Nonetheless he estimated the entire job would be under $50 plus shipping. Very nice people at both White's and in Huston at TNR.
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Old 21-03-2009, 15:35   #86
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And a follow up:

Here's a few shots of my new rig shined up with its temporary mirror. Had a local glass guy fabricate it while the original flat awaits re-silvering.

Enjoy.






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Old 21-03-2009, 15:46   #87
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RBEmerson et al:

Re older reditions of Bowditch, if interested, have a look at ebay. I browsed through the listings the other day, and there was what seemed a quite wide range of editions, at a quite wide range of prices.

At ebay, type in books, then Bowditch. Interested persons might also try amazon.com.
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Old 24-03-2009, 18:40   #88
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I have both a plastic Davis and a metal Astra. The plastic one works great--especially on a moving sailboat, and it's nice and light. But there's one trick: make sure that it is up to temperature before you use it. If you take it out of a cool dark place into the hot sun, you can watch the index error climb. So make sure that it sits out for awhile, and if possible, take index error measurements both before and after your sights. Having said that, I enjoy the handling of the Astra more. Since it's probably cheaper to buy a backup GPS (or two), choosing a sextant has become a purely romantic notion.
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Old 24-03-2009, 19:34   #89
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Something to be said for the Astra's bigger mirrors, more varied filters, and better optics, too.
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Old 24-03-2009, 22:43   #90
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Skookem nice, did you ever nav the old way?, I did but now my air sight red tables are out of date
Does anyone use weems plath starfinder and if so what year would one use for LHA, In the up to year 2000 air sight reduction tables
this is my sextant, still dunno the real make, but it is from German Democratic Republic, it was extremely accurate
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