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Old 09-05-2016, 10:12   #16
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Re: Sextant, what to buy?

I've navigated to Hawaii from the West Coast twice with a Davis Mk. 25 sextant, and it worked well. I didn't notice any "screw slop" in the worm gear, but I did adjust it prior to every sight, which takes all of about 30 seconds. Some people prefer the heft of a metal sextant to reduce hand motion, but I found the Mk 25 to be perfectly adequate on a 24' 2000# sloop.

You can also practice sun sights with a small pool of water that's used to reflect the sun's rays. Too hard to explain it adequately here, but presuming the altitude of the sun is below 45 degrees, you can shoot down into a pool of calm water and measure double the actual altitude.

Digital watches have made all this much easier. When I sailed across the Pacific, quartz watches were just becoming popular, and it largely eliminated time corrections.

Davis also makes worksheets for HO 249 V2 which are very handy, as it any celestial program or calculator.

Whether or not you use a sextant to navigate, it will fill you with wonder about the order of the universe. A good celestial sight reduction is as close to religion as anything I can think of.

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Old 09-05-2016, 10:27   #17
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Re: Sextant, what to buy?

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Originally Posted by Snowpetrel View Post
Something like a Davis Mk 3 is fine for emergency use and learning. I wouldnt go anything more expensive in the plastic. $100 should get you a new mk3

If you enjoy using it then a secondhand metal one for around $600 is a lovely thing to own and use.
An all metal sextant is worth the price if you want reasonable accuracy in long distance navigation. The best is a Plath. Very little error, resells well, durable(we dropped ours many times over 30 years of sailing), and heat extremes will have little effect on it.

We had a Davis backup and occasionally used it. Lots of error to adjust out of it and only good for one or two sights on a hot day. For day or weekend sailing not a big deal, but when you are trying for a 1000 n.m. landfall, a really big issue.
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Old 09-05-2016, 10:52   #18
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Re: Sextant, what to buy?

I have 2 sextants aboard; a TAMAYA and a Plath. If you want an accurate instrument I'd go for one of these brands. You can find them on EBAY. Then there are the cheaper Chinese sextants - ASTRA 3B- that go for about $400 and are reasonably accurate. Haven't had much practical experience with the Davis brands except in 1968 in Vietnam sitting on the top of my hooch with a Davis 25 taking sun shots off the South China sea and an average accuracy of about 6 miles. They've probably improved since then (or maybe I have). The question is why do you need sextants at all with GPS. Well, I am a belt and suspenders type of guy that always worries about what could happen if - say a lightning strike fries all of you electronics mid-ocean on your way to somewhere. At least you could sail down a noon (LAN) latitude to get where you're going.
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Old 09-05-2016, 11:10   #19
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Re: Sextant, what to buy?

I love my Freiberger, really nicely made instrument. Have used Plath's and Tamaya's in the past as well. Any of these are excellent choices.

There is nothing like having the confidence to navigate celestially with proficiency, not to mention its also a lot of fun!
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Old 09-05-2016, 12:01   #20
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Re: Sextant, what to buy?

If you get a great deal of joy using a really beautiful instrument then buy one of the better metal sextants. If that's not the case and you only want it as some form of backup if the world comes to an end or simply enjoy learning a very old art then spend less and get a Davis 25. I used one of these for several offshore passages many years ago and always got to where I was going.
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Old 09-05-2016, 12:17   #21
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Re: Sextant, what to buy?

IMHO the average sailor on a small (under 100') boat has not the necessary skill to get the accuracy that a good metal sextant is capable of achieving. My father, a merchant seaman, could achieve that accuracy because he was on a fairly stable platform, he was high enough above the sea that the horizon he was seeing really was the horizon and not just an abnormally high wave, he was on a vessel large enough that there was no significant difference in elevation of the ship under normal conditions between troughs and peaks of waves because the ship spanned a number of each, and his skill was such that he could make the necessary sight quick enough that his arm remained steady. On a small sailboat in the Pacific Ocean I have often had to hold the sextant for a few minutes before the combination of the boat being on the peak and not bouncing too severely to get the sight occurred. I suggest that before one buys a metal sextant that he/she first see how steady their arm is after holding the sextant (or equivalent weight) up in the sighting position for 5 minutes, while just holding the other arm in about the adjusting position at the same time. Sure, you must make certain adjustments more often with a plastic sextant, but they are MUCH easier to make than on a metal sextant when (not if) necessary. And, when the boat takes an unexpected role (note the "when" noit "if") and you have to let go of the sextant to hold on to the boat it'll be a much easier jerk on your neck by the lanyard (the lanyard IS around your neck?). Further, if the sextant swings as it drops on the lanyard and hits the boat two things are likely to happen with a metal sextant that are unlikely with a plastic one - the metal one is likely to chip the gel coat (or paint) and the metal one is likely to get further out of adjustment than the plastic one. (Some real expensive metal ones can only be adjusted by a techition that can bend the frame back to the correct shape.) And, if worse comes to worst and you lose it overboard your spouse is less likely to divorce you.
With a very stable platform, adequate elevation above the water, and great skill I believe that a metal sextant is justified. But by the average small boat sailor - no. Though maybe you're the type that would prefer owning an expensive but delicate coat and be afraid to wear it in very bad conditions than a practical Pea coat. (Of course the obvious solution is to have both. One for show and the other for use. If you can afford that.)
But I agree with the statement by Offshore 1960 that celestial navigation is fun - and it's something to do during the boring times. You've heard the statement that passagemaking is periods of shear boredom interspersed with moments of shear terror.
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Old 09-05-2016, 14:20   #22
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Re: Sextant, what to buy?

I learned to use one when I was 12 on the Jersey Shore.
Still have my fathers Cassens & Plath, a true work of art, pleasure to use.
We had a plastic one for backup about 20 years ago, but next to the Cassens & Plath it felt very crude.
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Old 09-05-2016, 14:34   #23
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Re: Sextant, what to buy?

Seelevel-
I would say "wait."
Get hold of Mixter's "Primer of Navigation" which is exactly that, takes you from the stone age to pre-GPS and makes very simple and rational explanations of how things work. See if there are some sextant courses near you (offered by many seaport museums and planetariums) and try to lay hands on a few to compare them.
There are a lot of subtle differences that don't get mentioned. With some, as you swing the sextant to check for level, your eye will turn the focu sof the telescope. Duh? With others, the "turning" is done from the front and your eye can't mess that up.
With the Plath Ultra, if you take a star sight you will see a slight red cast to one image, a slight green cast to the other--and they snap into white as they align, making the alignment VERY exact and easy. As far as I know, that's not documented anyplace.
A lot of features and variations don't make any difference when you are reading about sextants, but may make the difference in your preference once you've met them.

And that's ignoring the larger question of whether to buy one at all. First, you have to know that you can do the math and get it right first time, every time. A friend of mine poo-poo'ed using electronics, while I did a sight reduction within a few miles and they were trying to figure out a 900 mile manual error. But then once you use electronics...Sure, the GPS system may go down. Unless you're trying to escape to a small island, you can still find a coast without them. And if you DROP a sextant...tinkle tinkle, it is no better than a GPS anyway.

Just things to consider. Take your time, what's on the market will still be on the market, no fire sales needed.
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Old 09-05-2016, 14:57   #24
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Re: Sextant, what to buy?

I have a Freiberger from new and it's extremely accurate. It was given to me by my father in law, an agent in Denmark for the Admiralty Charts for commercial vessels and a captain himself. However, if I were to choose one myself I would go for the Astra. It's rugged and precise. Check out the S/V Navigator films on Youtube or Vimeo. They're great for a closer study of celestial navigation. The problem with sextants, sight reduction tables, the almanac and plotting sheets is that you have to practise it all the time not to forget it - like an unspoken language.
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Old 09-05-2016, 15:08   #25
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Re: Sextant, what to buy?

We have an inexpensive German alloy one like here: (https://www.dorotheum.com/en/auction...n-sextant.html) and a plastic one (Davies or Plastimo, I can't recall now). The plastic one is very inaccurate but it is very light and I think some sort of a backup should I drop the alloy one.

If I were to buy another, I would pay attention to weight. I would buy a quality instrument but I would shop for the lightest one.

I think C&P and Tamaya are common and much liked species.

If you are new to sight taking, I think you will make yourself a favour by buying a plain sextant up first, learning the actual skill with it (it is not the sextant that does the trick, it is YOU) and then buying the real thing last.

Buying the quality instrument later gives you plenty of time to shop around and find the best deal. There are deals.

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Old 09-05-2016, 16:28   #26
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Re: Sextant, what to buy?

i took a course, with a davis worked good however a nice metal one would be nice. guess it depends how much you would use it.
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Old 09-05-2016, 16:52   #27
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Re: Sextant, what to buy?

I am pleased to hear the davis Mk25's are working well for some of you. I figured they can't all be bad, and cant all have as much slop in them as mine. And in truth I can get within 10 miles, and probably less if I did proper averaging.

Ive been spoiled on ships with a level platform and top notch metal sextants which usually give very good results and the davis MK 15 disappointed me. Especially when I consistantly got better results with a much cruder vernier type.

The slop certainly isn't the normal side or perpendicularity errors. It is impossible to get the index error out. Read it with the screw turning clockwise and it is different from when the screw turns the other way. Might just be a flaw with my sextant. It's a shame because I like the feel of the sextant, and it has sentimental value. But I still carry it as a working spare, It just really annoys me everytime I use it!




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Old 09-05-2016, 17:42   #28
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Re: Sextant, what to buy?

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Originally Posted by Snowpetrel View Post
I am pleased to hear the davis Mk25's are working well for some of you. I figured they can't all be bad, and cant all have as much slop in them as mine. And in truth I can get within 10 miles, and probably less if I did proper averaging.

Ive been spoiled on ships with a level platform and top notch metal sextants which usually give very good results and the davis MK 15 disappointed me. Especially when I consistantly got better results with a much cruder vernier type.

The slop certainly isn't the normal side or perpendicularity errors. It is impossible to get the index error out. Read it with the screw turning clockwise and it is different from when the screw turns the other way. Might just be a flaw with my sextant. It's a shame because I like the feel of the sextant, and it has sentimental value. But I still carry it as a working spare, It just really annoys me everytime I use it!
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G'Day Ben,

It has been quite a few years since we used a MK25 going to Hawaii and back, but I don't remember having that much slack in the adjusting screw. what you describe would be pretty annoying, for sure!

But really, as Sam Crabtree says above, when taking sights from a small yacht, bouncing about in typical oceanic swell/wave conditions, and with a height of eye often less than the wave heights, the absolute accuracy of the sextant is not a big factor in accuracy of the sight. And in the majority of navigational situations, a five mile error isn't a too big deal. If one is close enough to shore to require better accuracy, eyeball tech is often better suited than celestial!

None the less, the pleasure of a tiny cocked hat after a round of stars is a nice reward for one's work!

Cheers,

Jim
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Old 09-05-2016, 18:36   #29
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Re: Sextant, what to buy?

I used a Davis 25 for several years and found it was without slop. When GPS first came out I bought one but I still did regular sights and I found I could get pretty much a 5 mile average on the Davis which is about as good as one could expect. Those were 3 sight averages on running fixes. I might have spent more on a metal one back then but my budget was a lot tighter than it is today.
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Old 09-05-2016, 19:44   #30
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Re: Sextant, what to buy?

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It seems the sextant remains a basic component in a sailors kit, so which model should I purchase? Are plastic worth the while? What is the preferred make and build material?
Cheers.
I have an Astra III B, That is brand new, never been out of the box. I simply never had the urge to get it out and use it for real. I had a Davis as well and did use it a bit. If your interested in the IIIB you can have it for $250 plus shipping. You can get in touch with me at the following:
W. "Butch" Lester at:
wle0423@live.com
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