Davis Mark 3 Plastic Sextant


Instruction manual included.
Sextant weight is 6 oz.
Shipping weight is 2 lbs.

All plastic sextants are inspected at Starpath before shipping.

On back order. We hope for delivery early August.

$119.00   ...item# 1840d3

Davis Mark 3 Plastic Sextant
A forerunner of this instrument was developed for emergency use during WWII, called the "Lifeboat Sextant." This is the least expensive sextant in the world that will provide dependable accuracy adequate for actual ocean navigation. With good procedures you can obtain some 5 to 10 miles position accuracy routinely, and better with practice, providing you follow the careful procedures outlined in our books on plastic sextants. There is also a good User's Guide.

All replacement parts (even the screws!) are readily available. There are no optics nor telescope, and the vernier can only be read to the nearest 2', so we need to take multiple sights and average them to obtain good lines of position, and the fixes themselves are best made from three bodies properly selected, as explained in our books.

This sextant is popular as a back-up or learning sextant, but aside from these celestial applications, it is actually the sextant of choice for inland and coastal piloting. Using the sextant horizontally, you can find your position on a chart much more accurately than you can by other conventional piloting techniques such as compass bearing fixes.

For reference see this Comparison of plastic sextants.

In short, even if you never plan to sail offshore and need celestial navigation, we still strongly recommend this device for inland and coastal piloting. Without GPS or radar, this is your most powerful tool for finding and keeping track of position in sight of land or lights... or for monitoring if you have dragged anchor.

These are great instruments and a joy to use for piloting. It is actually difficult to imagine how these piloting techniques seem to have faded away. Some time around 1950 they were not even covered in Bowditch any longer. From the 1800s to 1930s leading navigation texts devoted entire chapters to the subject. We preserve and elaborate on these methods in our course materials, since the simple design of the Mark 3 makes these sights very much easier than they are with conventional sextants.

Below are pictured the Mk 3 in it's standard package, along with two optional supporting booklets.

Plastic case option

See Books catalog

See Books catalog

If your sextant goal is primarily to just have a prudent backup to the GPS, then you might consider our GPS back-up kit that includes a Mark 3 in a hard plastic case. It can simply be added to the boat without further thought, and opened if ever needed. No special knowledge or training needed.


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