Can I use an old sextant?

[tim]

I've just inherited my grandfather's sextant. It's of 1911 vintage and is in the orginal box with the certificate.

Is it likely to be suitable for use (it seems to be in good condition)? Is it possible to get them serviced?

Regards,

Tim

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[BarryH]

You could try <A target="_blank" HREF=http://www.norcom.demon.co.uk/meridian/showroom.htm> these </A> people. Might be worth having a chat with them, nothing to loose

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[webcraft]

If it is a good quality sextant (ie of metal construction and by a reputable manufacturer) then there is absolutely no reason why you shouldn't be able to use it.

Get yourself a suitable book - there are various checks you can perform to assess the accuracy and calibration of the sextant.

- Nick



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[Rowana]

I sort of gather from your post that you've never used a sextant yourself.

My first move would be to find someone in your area (you don't say where you are in your bio), who is familiar with sextants, perhaps your local yacht club? They would be able to advise you as to if it requires any adjustments. Most of these you can do yourself, once you know what you're doing.

Let us know where about you are, and perhaps there is a S/butter local to you who could assist.

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[Guest]

A sextant is sextant is sextant ......... it does not matter how old it is - as long it is not damaged.

Servicing a sextant ??????? Find a friendly Merchant Navy Deck Officer or ex one like me and he'll check it out ..... even correct errors if found.

The only thing that really needs 'servicing' is the threaded section and micrometer / vernier. And that is with very light Sewing machine oil.

The Sextant hasn't changed overall design principle in a lot of years - literally since changing from the Octant.


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[Birdseye]

try using it a few times before getting it serviced. then when the novelty has worn off and you realise that it is 19th century technology and as relevant to today as a clockwork watch, you can save the money, buy a decent handheld gps, and use the sextant as a no doubt attractive table ornament.

great things to have and handle, but very definitely superceded IMHO

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[Guest]

Depends on what he wants to do with it .......


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[AndrewB]

It could be OK, but more likely by now it will no longer be good, except perhaps for practice. With time, brass sextants are prone to problems that cannot be cured, such as the frame warping. If it has ever been dropped that is likely to have made it unservicable.

Older sextants used verniers for precise measurement and often where these have been cared for by people who do not understand these instruments they have been polished to the point they can no longer be read. Verniers often relied on a magnifying sight which becomes easily damaged or clouded. The silvering of the mirrors tends to fail, though this can be corrected.

The acid test is to use it for measurement. Stand in a known position and see whether, with all the 'correctable' adjustments made, it will measure the sun's altitude accurately to within 5 minutes of accuracy. Then measure a horizontal angle between two objects on a far shore to the same degree of accuracy.

If it seems to pass these tests, then the final step is to get it re-certificated, which needs to be done to all working sextants every decade or so. This is not cheap, but will correct minor errors and provide a correction table if necessary. <A target="_blank" HREF=http://www.kelvinhughes.co.uk>Kelvin Hughes</A> used to specialise in yacht sextants, and would be worth approaching.

Otherwise, it sounds like a nice heirloom, and will be valuable as such.

 

[ccscott49]

But.....the stars are older now, they may have moved!! You need the latest sextant, I replace mine every five years.

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[Guest]

Do I detect a wind up ??????

I take it you are talking Plastic jobbie ???? I wouldn't like to replace a Tamiya or Plath every 5 yrs !!!!

<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[ccscott49]

Re: Do I detect a wind up ??????

Yes! You do detect a wind up, mine is a very good/expensive east german one aswell! I can never remember the name!!

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[MainlySteam]

Re: Do I detect a wind up ??????

<<<very good/expensive east german one>>>

Probably a "fry a burger" one in that case.

John

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[tcm]

have you tried the new garmin GPS sextant? Very good i hear.

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[MainlySteam]

I heard the same. But when I tied one I found it very hard to bring the satellites down to the horizon so I couldn't get an accurate altitude. Maybe there is some knack I don't know about?

The other thing too is the satellites move so fast compared to stars.

John

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[tim]

I have 3 GPS's (either rely on 1 or 3, but never 2).

I seems like another useful skill to have, and I think that by learning celestial nav it will improve my understanding of the earth, planets, orbits etc.

Tim

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[ccscott49]

Re: Do I detect a wind up ??????

Thats the swine, had to send it to the conservative club for calibrating, to get the socialism out of it!

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[ccscott49]

They're very good, but everytime I take it out of the wheelhouse it stops!

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[Twister_Ken]

Learning to use the sextant will not only tell you very roughly which ocean you are in but will develop other useful skills such as not falling overboard when two hands are holding the sextant and the third is operating a stop watch. If you want to go the whole hog, you're going to have to do some pretty complicated sums as well while sitting at a pitch and toss chart table, although well after your grandfather's day people did start cheating by using programmable calculators.


<hr width=100% size=1><A target="_blank" HREF=http://www.writeforweb.com/twister1>Let's Twist Again</A>

 

[Mirelle]

Agree, mostly.

I slightly disagree about measuring the Sun's altitude from a known position as a check - there are plenty of ways for human error to creep in to that one!

It may help to lay hands on an old textbook - sextants changed a great deal in the 50's and 60's. As Andrew says, if you can correct out the correctable errors, you have a good basis for taking things further. Since it is an heirloom, it has probably avoided many of the dreadful things that the "antiques trade" does to sextants, like polishing them, fiddling with the adjusting screws, and so on.

The practical differences are these:

1. Small mirrors and awkward telescopes - this is the biggest difference.

2. Vernier not micrometer.

3. No light, but that's only of relevance for star sights

4. Need to change telescopes more often.

5. Often awkward to fit in its box (mind you, my 1970's Plath has a box designed by an evil gnome!

I would go ahead and start trying it.



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[Rowana]

Get a book . . .

I have two books -
"Celestial Navigation for yachtsmen" by Mary Blewitt ISBN 0-7136-4623-3
"Celestial Navigation" by Tom Cunliffe ISBN 1 898660 75 1

Both are around the £9 mark. I prefer the Tom Cunliffe one, but that is just because of my own personal style. The other one may suit you.

I would try your local library or bookstore first, and see which one suits you.

As I said in my earlier post, someone local to you may be able to assist. The may have the required tables, and be up for taking you out for a go.

It's a lovely keepsake whatever you decide. Which shipping line did your grandfather sail with?

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