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11-04-2017, 20:51
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#1
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Registered User
Join Date: Jun 2010
Location: Bay Area
Posts: 235
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Sextant restoration and/or calibration
Anyone have a resource for a Co that restores sextants or calibrates them? Im thinking about getting a used sextant and would like ot have it checked out? Or should I just get a modern day plastic one?
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11-04-2017, 21:03
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#2
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Registered User
Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,919
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Re: Sextant restoration and/or calibration
Any well looked after sextant of reasonable quality shouldnt have any major errors that can't be fixed easily by adjusting the mirrors. If the issue is bigger than that, prehaps a worn pivot or warped or bent frame its probably not worth rebuilding.
A great resource is the sextant book. Most of the metal sextants are a fair jump above the plastics in terms of accuracy and pleasure of use. But the plastics work well enough offshore to get you across an ocean.
Sent from my SM-G930F using Cruisers Sailing Forum mobile app
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11-04-2017, 21:15
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#3
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Registered User
Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
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Re: Sextant restoration and/or calibration
What Snowpetrel said. And to expound on the comment on plastic ones. Generally when you shoot fixes with them, the area of uncertainty will be larger than with a good metal one. Which is fine out on the ocean, but not when within sight of land.
__________________
The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
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11-04-2017, 23:10
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#4
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Registered User
Join Date: Mar 2007
Location: Santa Cruz
Boat: SAnta Cruz 27
Posts: 6,734
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Re: Sextant restoration and/or calibration
Even the best metal sextant which has been lovingly refurbished will not tell you where you are the 0.01% of the accuracy of the cheapest GPS. That's why they have gone the way of the dodo bird. If you want to pretend you are an old sea captain, you might as well use a plastic one. The Davis Mark 25 with the beam converger is easier to use.
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11-04-2017, 23:55
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#5
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Registered User
Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,919
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Re: Sextant restoration and/or calibration
Very true about the sextant accuracy vs GPS. I still like carrying one offshore, but I am happy enough not to these days as well, given enough backup GPS units. Ive got a davis 15, and a very nice metal frieburger. The 15 has let me down accuracy wise with a worn thread over the zero index region. I am not sure of its history. It was my grandfathers, and may have been used for training, hence the wear and slop in the micrometer, so is only accurate to about 15' or so.
A mark3 I used gave more honest results with a simple vernier, good to about 5-10' or so. I used a new mark 15 coming back from antarctica recently and my first sight was within a few miles of our real position and a new mark 25 I used on passage to Chile also gave excellant results, consistantly within 5' and often better, so the plastics can work. If I was buying a plastic one for myself I'd get a mark 3. And save the money towards a metal sextant in the future. But a mk 15 or 25 is much nicer to use than the mk 3 with its fine adjustment and micrometer.
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12-04-2017, 05:32
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#6
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,384
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Re: Sextant restoration and/or calibration
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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12-04-2017, 05:47
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#7
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Registered User
Join Date: Feb 2017
Posts: 33
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Re: Sextant restoration and/or calibration
Quote:
Originally Posted by donradcliffe
Even the best metal sextant which has been lovingly refurbished will not tell you where you are the 0.01% of the accuracy of the cheapest GPS. That's why they have gone the way of the dodo bird.
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GPS...Yeah, poor people, they did not knew what they are missing
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12-04-2017, 07:52
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#8
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Registered User
Join Date: Feb 2016
Location: forest city
Boat: no boat any more
Posts: 2,511
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Re: Sextant restoration and/or calibration
second that! very satifying to have the palmtops creep over the horizon after taking starsights all through the early hours of the morning by the light of the full moon...very!
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12-04-2017, 09:08
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#9
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Registered User
Join Date: Oct 2016
Posts: 43
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Re: Sextant restoration and/or calibration
Sextants and GPS
As a professional navigator who sailed umpteen thousand miles in the days before GPS and afterwards, All I can say is that I noticed no difference between the two eras, why do you need to know exactly where you are in the middle of an ocean, and when coasting you really should be looking out of the window or over the gunnel rather than at a bunch of electronics. Also though there are now various systems most receivers use the USA GNSS system, what are you going to do if it gets switched off or the code changes to fit a military application which of course is it prime reason for being, or god forbid some idiot sets of a 1 kiloton nuclear air burst which fries all the un -hardened electronics we now use.
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12-04-2017, 09:57
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#10
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Registered User
Join Date: Aug 2015
Location: Back in Mexico cruising the northern part of Sea of Cortez
Boat: 1999 Pacific Seacraft 40
Posts: 720
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Re: Sextant restoration and/or calibration
Quote:
Originally Posted by dofthesea
Anyone have a resource for a Co that restores sextants or calibrates them? Im thinking about getting a used sextant and would like ot have it checked out? Or should I just get a modern day plastic one?
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You can call and talk to the techs at Captain's Supplies (formerly Captain's Nautical). The repair and refurbish quite a variety of marine instruments including sextants. They are located in the Ballard area of Seattle.
https://www.captainsnautical.com/
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12-04-2017, 10:28
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#11
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Registered User
Join Date: Aug 2011
Location: New York, New York
Boat: Dufour Safari 27'
Posts: 1,909
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Re: Sextant restoration and/or calibration
Quote:
Originally Posted by dofthesea
Anyone have a resource for a Co that restores sextants or calibrates them? Im thinking about getting a used sextant and would like ot have it checked out? Or should I just get a modern day plastic one?
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Try New York Nautical
200 Church Street
New York, New York 10013
(212) 962-4522
www.NewYorkNautical.com
The last time I was in there several months ago they were repairing a number of sextants. Good luck with your repair.
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12-04-2017, 12:33
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#12
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Marine Service Provider
Join Date: Dec 2011
Posts: 1,540
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Re: Sextant restoration and/or calibration
There is one in Seattle. Can't remember the name. It's on the street that runs north and south on the west side of Queen Ann Hill and over the Ballard bridge. Usually cheaper to buy new rather that overhaul unless you have a valuable museum piece.
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12-04-2017, 18:06
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#13
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Registered User
Join Date: Apr 2012
Location: Bowral NSW Australia
Boat: Roberts Tom Thumb 24
Posts: 11
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Re: Sextant restoration and/or calibration
The sextant is still one of the handiest, and safest,instruments when coastal cruising. As it records in degrees true, as do paper charts, it is a cinch taking sextant horizontal sightings combined with a three pointer plotter and - voila ! - where you mark, that is where you are.
AND there is no way you can have a power failure!!
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12-04-2017, 19:27
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#14
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Registered User
Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
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Re: Sextant restoration and/or calibration
People seem fixated on sextants for purely celestial nav, but they have a lot of other navigational uses, including coastally & piloting. Such as determining ranges to various known objects. And when you're navigating, the more ways you have to cross check your position the better. Relying on only one source of data for your position amounts to poor seamanship, period. Regardless of what that data source is. GPS, or other. Particularly as there are plenty of incorrect charts out there. Incorrect in that they were created based on surveys done a decade, or a century ago. And or, that things have changed in the area that you're currently navigating in. Such as that new channel that's being dredged, or underwater obstructions in an old but commonly used one, etc.
__________________
The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
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12-04-2017, 20:14
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#15
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Registered User
Join Date: Dec 2009
Location: Bundaberg, Qld.
Posts: 2,192
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Re: Sextant restoration and/or calibration
Quote:
Originally Posted by UNCIVILIZED
Particularly as there are plenty of incorrect charts out there. Incorrect in that they were created based on surveys done a decade, or a century ago. And or, that things have changed in the area that you're currently navigating in. Such as that new channel that's being dredged, or underwater obstructions in an old but commonly used one, etc.
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1. If you have the current edition
2. If you know how to read them eg; error/zone of confidence, or “ZOC” notes.
3. If you know what Notices to Mariners are and how to get them (including T & P's)
4. And know how to apply them
Then most of the above shouldn't be to much of a problem, having said that, "bumps in the road" are still found today and will continue to be found for some time yet. Those newly found nearly always end up as a correction on a chart (literally thousands are every year worldwide) so if you luckily or unluckily find one, report it to the correct authority (and not just some crowd sourcing app distributor), ongoing official hydrographic surveys aside, that is how it's done............
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