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Comment by dreamcompiler | Hacker News Reader

Anybody know where to buy a good sextant? (I hope the course discusses this; I haven't had time to read it yet.) I started trying to learn this stuff a few months ago and it seems that most available sextants fall into two categories: Cheap plastic ones with poor thermal characteristics that make them inaccurate, and expensive brass ones that are more thermally stable but designed for display and not calibrated for serious navigation. I'd like to buy one in between: A quality navigational instrument that doesn't have to be "pretty".

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I would suggest subscribing to navlist at fer3.com, and reading through the many old threads there about this subject to get a general idea. In my experience the good and the bad sextants are all mixed on the auction sites. You can always post a picture there before you buy...

Personally I'd never buy a new one, since a second hand one is just as good (if you have a bit of knowledge and avoid broken ones). A sextant doesn't need calibration beyond what's done at the factory and what you can do yourself. On top of that most have been very lightly used.

If you're interested in the instrument itself (rather than simply how to use it as a tool), 'The Nautical Sextant' by Bill Morris is a superb book: https://www.amazon.com/Nautical-Sextant-W-J-Morris/dp/093983... .

Good suggestions from others and I know this is not your use case but I'd add to anyone new to navigation or with just a casual interest: get a plastic 'emergency sextant' and try using it along with a digital watch (Casio cheap one). Davis and EBBCO do both do plastic sextants.

There is even a book on how to use them called "How to Use Plastic Sextants" by David Burch who seems to be a fairly prolific author on celestial navigation http://a.co/0iVNVrW

Linked to that book page on Amazon is the Davies 'quick reference card' (laminated) that I imagine one would have in the life boat...

This site seems to have a good selection: https://www.celestaire.com/ . A person commenting in the San Francisco Amateur Astronomers facebook page where I posted this course mentioned they have an Astra III-B

Any good nautical store should have them. Obviously, you'll find those only at the coasts or near rivers.

I can recommend American Nautical Services[0].

[0] https://www.amnautical.com

Harbor freight used to sell a brass one. Haven't checked in a while, but it might be something nice.

https://www.harborfreight.com/brass-sextant-66096.html

That is a typical 'decorative object', not a sextant fit for purpose. They've been flooding auction sites in hundreds of variations, often 'antiqued' and made to look superficially like real 150 year old sextants.

Imagine staring into the sun through that telescope using only that coloured green glass as a filter. Goodbye retina!

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