For Sale: Mark 15 Sextants

[valg0239]

I have three Davis Mark 15 sextants for sale. They were used very little and are almost in new condition. I'm asking $75.00 each and will include shipping to any USA destination.

[windtraveler]

I just joined the forum. Do you still have your sextants for sale? Are they accurate? I've never used one but we're planning a circumnavigation in about a year and a half and would like to start learning celestial navigation. Is there anything that makes one better for learning than another? Thanks, Scott.

[AnchorageGuy]

What is a sextant?

[bob_77903]

Not sure...But i heard you could see one at the Smithsonian....

[valg0239]

They are good enough for celestial navigation across the oceans of the world. However, the accuracy of these sextants is basically determined by the experience of the user. It would be a good backup device should your GPS get lost or broken. There are adjustment on the sextant to improve accuracy but, again, that is determined by the user. If you have any further questions, please let me know.

[valg0239]

It is an instrument which allows you to locate your position on the oceans of the world by taking altitude measurement of various celestial bodies and doing computations to locate your position on the earth.

[cabo_sailor]

The only problem with them is that they are plastic and dimensionally unstable depending upon ambient temperatures. As a backup to gps or as a learning instrument they are fine. If your primary means of navigation is to be celestial, then you probably want to go to a metal sextant such as the Astro IIIb.

Supreme accuracy as represented by high end sextant's costing thousands is hardly necessary. Keep in mind the relatively small, very mobile, platform that sights are being made from.

[valg0239]

Originally Posted by cabo_sailor

The only problem with them is that they are plastic and dimensionally unstable depending upon ambient temperatures. As a backup to gps or as a learning instrument they are fine. If your primary means of navigation is to be celestial, then you probably want to go to a metal sextant such as the Astro IIIb.

Supreme accuracy as represented by high end sextant's costing thousands is hardly necessary. Keep in mind the relatively small, very mobile, platform that sights are being made from.

Your absolutely correct. I can recall flying across the Atlantic ocean and taking celestial shots while we flew at 480 knots and then plotting a fix on a chart that only a few feet across. It's like finding a needle in a haystack. Anyone that can consistenly shoot within half a mile is a hero in my book!

[valg0239]

our absolutely correct. I can recall flying across the Atlantic ocean and taking celestial shots while we flew at 480 knots and then plotting a fix on a chart that only a few feet across. It's like finding a needle in a haystack. Anyone that can consistenly shoot within half a mile is a hero in my book!

[amarinesurveyor]

I you set the Mark 15 out in the air to get it stabilized with the temperature, then you can usually get your sights done without any appreciable movement out of adjustment. After you set it out you have to zero it out and check it.
I used a Mark 15 for practice and some short trips, but did a trip from St. Thomas to Bermuda using it in 1985. This was before GPS, so all we had was Loran which had no signal in that area. There was another on board that had a high priced metal one and we were both taking our fixes and plotting our positions - we used sun shots and did running fixes as well as some star sights when we could get them. To make a long story short, both of our fixes were pretty close together as we neared Bermuda and we made our landfall close to when we thought.
The moral of the story is you don't have to have an expensive sextant to find your way! Although his sextant really had a nice feel to it.
Brian

[jheldatksuedu]

The mark 15 is perfectly good to use, on a sailboat if you can find your position within 5 miles you will get to where you need to be. I use GPS, but have and have practiced with the mark 25 and done quite well. It's my backup to the electronics, then I have a mark 15 and another even cheaper mark III that also works in a pinch, it would get you to land at least. The difference in the 15 and 25 is in the horizon mirror, half mirror, split image and half silvered, composite image. Jon

[Jim Cate]

A shocking number of years ago Ann and I did our first off shore passage -- SF to Hawaii and return. Did it with a plastic Mk 25 and zero at-sea experience. OUr landfalls at both ends were adequately close, and, incidentally, two of the most satisfying accomplishments of my life! For later voyages I bought a Zeiss metal sextant. Much better optics, more stable calibration,etc. And while I found it pleasanter to use, the fixes were no better as far as the size of the cocked hats could show. Why? I reckon that from a small boat (30' S&S sloop) the motion plus the very low height of eye add by far the greatest errors, not the quality of the instrument.

So, go ahead and buy plastic, learn how to do the calculations, practice a lot, and if you are ever so unlucky as to have a lightning strike that takes out all of your GPS units (and this can happen) you will be bloody glad you did the homework. Good onya, mate! I wish that more aspiring cruisers were as thoughtful !

Cheers,

Jim and Ann s/vInsatiable II lying Gladstone Qld Oz

[Strygaldwir]

Store your hand held GPS in your microwave. Just kidding sort of. A microwave oven makes a great Farraday cage. The insides are protected from electrical voltage spikes.

But, who the heck has a microwave oven on their ocean going boat?!?

[Boomp]

They list for $200 at West so its a good deal!

[David M]

For yachts where your height of eye puts you much closer to the horizon combined with the much greater relative motion of small boat, a plastic sextant is fine. You would be lucky to get consistent three mile accuracy from a small boat anyways. From ships where the horizon is further away and the relative motion is less, you want a metal sextant where once you get good, 1 to 2 mile accuracy under good atmospheric conditions is pretty common.

I strongly disagree with the people who are completely reliant on GPS, who effectively state that celestial is worthless. Any sailor worth his salt understands the importance of backups. Stuff happens.