Purchasing a sextant


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jgbailey (Past OCC Member)
jgbailey
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I am considering buying a sextant but not sure at this stage whether it would be second hand or new. Having looked at a few brochures and on ebay the variation in specification seems bewildering.

Advice on the specification for a new sextant and what to look out for when buying second hand one in terms of condition would be welcome.

John B
Daria Blackwell
Daria Blackwell
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John, beware of buying sextants on eBay and amazon. Many are replicas made in India intended for decoration in personal libraries that have now entered the market as the real deal. The most reliable dealer for sextants is Celestaire.

The Astra IIIB and the Tamaya are top notch. We have one of each. Bought one from Celestaire the other via eBay. We 've used them to take noon sites but now they are pretty much gathering dust. Nevertheless, we still take them with us when crossing oceans just in case (having been struck by lightning on a previous boat we know what can happen to electronics). We also have Mary Blewitt 's book, a pocket computer that has a perpetual almanac in it, and Star Finder 2102-D, which are very useful accessories. Good luck.

Why not post a note in the eBulletin and in the for sale section of the forum to see if any member would want to part with theirs? Where are you located?

Vice Commodore, OCC 
jgbailey (Past OCC Member)
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Daria, thanks for the reply. I lived and worked in India so am aware of its potential.

Not sure if you can answer this. Do all sextants have a Collimation Certificate? If buying second hand how do you check it out in terms of accuracy? I am left handed, can you buy a left handed version?
Daria Blackwell
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John, I have heard that left-handed sextants are exceedingly rare. I have also heard that left-handers use sextants upside down but I can 't vouch for that. There is a very good blog about sextants here. http://sextantbook.com/category/unusual-left-handed-sextant/

Conincidentally, I noticed that the editor of our newsletter, Colin Jarman, has his Frieberger for sale on p16 of the current issue just mailed.

Vice Commodore, OCC 
nadezhda
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John. I used a plastic sextant for a while and got exceptional results from it. It also had the benefit of being lightweight so I could spend more time with it to my eye. I eventually decided to go posh and get a Cassens Und Plath which has wonderful craftsmanship but I don 't think it is any more accurate because I haven 't got any better at keeping a steady hand on a rocking boat.

If you need to use your sextant upside down then remember to stand on your head whilst doing so ;-)
Colin Campbell
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John
A few thoughts after dredging up what I thought I’d long forgotten from my time at sea:
A quality sextant should have a certificate with a graph or table of centrering errors against angle. A perfect sextant would have the pivot point of the index arm at the centre of the instrument and when this is not the case, an error usually in seconds is recorded which varies with the position of the index arm. A centering error of 1’ or 60” means you are starting with a 1 mile position error before you start on all the other variables. If you have the calibration certificate that appears genuine then you can atleast allow for the cerntering error in your sight calculations. No certificate, then you have an unknown variable.
Of the other 3 errors, Index error can be measured and allowed for, and perpendicular its and side error can be measured and corrected with the screws on the side of the respective mirrors (plenty of guidance on the procedures on line).
Hope that helps
Regards
Colin
Colin Campbell
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Following my last - perpendicularity is the word I intended to type!!
Regards
Colin
Roger Harris
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An original certificate is always nice to have. It tells us more or less when the sextant was made, and looks great pasted to the lid of the box. But it's not really essential when evaluating a potential purchase.

If you spoil yourself with a brand-new sextant, presumably the calibration will have been recently performed and the certificate reliable. However, the current form of some manufacturers' certificates merely states "free of errors for practical use" or something similar.

If you buy secondhand, the certificate probably indicates specific instrument errors at various stated angles. However, the calibration will almost certainly have been done at date of manufacture: probably >10 years ago. It may still be accurate, or it may not. Whilst sextants are not as fragile as people believe, they are precision instruments and an old certificate is no guarantee of current condition.
 
So, in my opinion a certificate is like the dust jacket on a hardcover book: desirable, aesthetically pleasing, but not strictly necessary.

Dick
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Roger Harris - 16 Feb 2021
An original certificate is always nice to have. It tells us more or less when the sextant was made, and looks great pasted to the lid of the box. But it's not really essential when evaluating a potential purchase.

If you spoil yourself with a brand-new sextant, presumably the calibration will have been recently performed and the certificate reliable. However, the current form of some manufacturers' certificates merely states "free of errors for practical use" or something similar.

If you buy secondhand, the certificate probably indicates specific instrument errors at various stated angles. However, the calibration will almost certainly have been done at date of manufacture: probably >10 years ago. It may still be accurate, or it may not. Whilst sextants are not as fragile as people believe, they are precision instruments and an old certificate is no guarantee of current condition.
 
So, in my opinion a certificate is like the dust jacket on a hardcover book: desirable, aesthetically pleasing, but not strictly necessary.

Hi all,
This is a very old thread, so the the poster is probably made his/her decision.
One thing I note, is that it was never determined how the initial poster intended to use the sextant. If as an emergency piece of kit, a decent plastic one would likely suffice. If intended for hobby , then personal finances likely played a part in the decision. And, within reason, money makes a difference. Taking a sight with a good well made traditional sextant is just a joy. Weight does make a difference, but a well balanced sextant is likely not to fatigue overly.
My best, Dick Stevenson, s/v Alchemy
Roger Harris
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This is a very old thread, so the poster has probably made his/her decision.

I hope so! But the thread lives on, and may perhaps be of some use to others.

If as an emergency piece of kit, a decent plastic one would likely suffice.

Agreed. And plastic can also be appropriate as a 'starter' sextant. Per Budlong, Sky & Sextant:

Many people start out with a plastic sextant for practice. After they’ve had some experience and know what to look for, they graduate to a brass one. I think this makes sense. They haven’t invested a lot of money right at first, and in the end they have a good sextant for regular use, and the plastic one as a spare.

Some navigators never "graduate" to a metal sextant, and of course that's fine too. Leo Goolden used an old Ebbco for his 2015 transatlantic and had no issues (though Tania Aebi wasn't quite so lucky!).

[A]nd, within reason, money makes a difference. Taking a sight with a good well made traditional sextant is just a joy.

I agree, Dick: top-quality sextants are a pleasure to use. And as a bonus, Budlong claims that mere possession increases one's longevity!

The quality and workmanship in one of these machines is something to behold. Just having one in the house will add joy to a rainy day and a couple of years to your life; using one is an experience in precision.

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