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Marine Resources 2017 728x90

US Navy Sextant Decision - wise for anyone offshore

by Martin Flory Group 4 Jan 04:47 UTC
From the left - Davis Instruments' Mark 25, mark 3 and Mark 15 sextants © Martin Flory Group

The US Navy reinstituted training in celestial navigation and sextant use due, in part, to concerns over intentionally jammed GPS satellite signals. More likely, professional mariners and recreational passagemakers could find themselves lost at sea due to electric or equipment failure. As a navigation backup, nothing beats a sextant from Davis Instruments. Combined with a wristwatch, copy of The Nautical Almanac and nautical chart, anyone can find their way home using only the sun and stars.

Whether student or experienced navigator, Davis Instruments offers three sextant models to fit any skill level. No one will say mastering celestial navigation is easy, but learning is a fun and rewarding pastime. Every Davis sextant comes with a detailed instruction booklet.

Built from rugged, corrosion-proof and dimensionally stable polymer, Davis Instruments Sextants are highly accurate. So much, in fact, that they're commonly used for circumnavigating. The affordable, yet full-sized Mark 3 Sextant is ideal for the beginner. Lightweight with a comfortable grip, it has an adjustable half mirror and four sunshades. Rather than optics, it uses an effective sighting tube. With practice, it makes moving on to a more advanced model a breeze.

The Mark 15 Sextant boasts features common in versions costing four times as much. It has a half-silvered mirror, adjustable index mirror, seven large sunshades and a 3mm x 27mm star scope. An easy-to-read micrometer drum vernier scale reads down to 2/10 of a minute of arc and its 18cm frame radius is graduated from 120 degrees to -5 degrees.

Davis Instruments' premier Mark 25 Sextant is an equal match to any high-end model on the market. In addition to all the features of the Mark 15, it features a Beam Convergerâ„¢ full horizon mirror, LED illumination and coated optics for superior low light transmission. It's built from upgraded materials throughout. For land-based practice or foggy mornings, Davis Instruments offers an Artificial Horizon. It's used to take sun or moon shots without observing a lake or ocean horizon. It can even be used indoors by a window.

An additional teaching tool is the Davis Quick Reference Celestial Navigation card, printed on waterproof plastic and loaded with useful information. 22cm x 28cm with standard three-hole punches, it has instructions for sextant use and corrections, a finder for 18 stars, data entry form, and step-by-step sight reduction and plotting procedures.

Contact Davis Instruments, Tel: +1-510-732-9229; Fax: +1-510-732-9188. In Europe: Davis Marine, Tel: +31 (0)78 6194316; Fax: +31 (0)78 6192689. Email: or visit

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