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Old 21-08-2019, 17:09   #1
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Sextant to Learn Navigation Old School

Looking to learn to use a sextant to navigate old school. ( In case of absolute disaster, or just because ) Looking to buy a sextant that is usable, but not the absolute best or most expensive. Amazon has a bunch of possibilities, just not sure what would be good, usable, not expensive, and reasonably accurate.
Anyone have any recommendations?
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Old 21-08-2019, 17:17   #2
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Sextant to Learn Navigation Old School

After you get a sextant, you going to a class, or using a book?
I ask as I need or want to also, I have a used sextant I bought here on the for sale thread.
However it’s my understanding that to teach the basics a plastic one is fine, but as I have no experience myself I can’t say for sure.

I looked into a class and it’s over $300 and didn’t specify how many days it was. Unless it’s several that sounds a little expensive to me.
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Old 21-08-2019, 17:20   #3
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Re: Sextant to Learn Navigation Old School

I'm biased..... but look below.....

A second hand Astra or Freiberger would be my suggestion.....
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Old 21-08-2019, 17:40   #4
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Re: Sextant to Learn Navigation Old School

The Davis Mk 15 or Mk 25 are fine for learning celestial navigation. You can find these for under $100. I wouldn't go with the Mk3 (triangle shaped).

EZ Celestial has a nautical almanac and site reduction apps which are quite good. Navigator is also a good resource, runs on Windows and IOS, with great documentation on celestial navigation.

There's taking the sites which is the fun/easy part (provided that you can see the sun/stars and horizon). Then, there's flipping through the Nautical Almanac and HO249 publications to compute your line of position. Once you understand the process, I find it easier to let a program/app do the site reduction.

You can find online nautical almanacs and downloads for HO249.

Every couple of years I go down to the beach and practice. Usually can't be bothered to do while underway.

Enjoy,
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Old 21-08-2019, 18:28   #5
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Re: Sextant to Learn Navigation Old School

Take a look at an app called CamSextant for the iPhone. Allows you to take sites and reduce them directly on the phone. It is great for learning but clearly the phone is not as accurate as a sextant. Still it will teach you the art and it gives you an immediate feel of where you are. For example, you point it at a star or planet, it tells you where it believes the object should be based on the assumed position, so you understand how the sky turns (oops, the Earth , with your changing position. Once you learn all of this, you will be in good shape. Eventually, if you are serious about this art, you may want to get yourself an electronic sextant with a built in horizon. You can use it anytime during the night and is much more accurate that a manual sextant.
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Old 21-08-2019, 18:56   #6
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Re: Sextant to Learn Navigation Old School

Davis Mark 25 used.


And before buying a book or two or paying for an app. Please watch this video. In my opinion this is the best celestial navigation course. It's in two parts.



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Old 21-08-2019, 19:21   #7
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Re: Sextant to Learn Navigation Old School

I have a plastic Davis. Just picked up a metal White WW2 sextant on eBay for $125. After a little online reading, was able to adjust out the error. It feels like a real sextant.
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Old 21-08-2019, 20:12   #8
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Re: Sextant to Learn Navigation Old School

I have a Davis Mark 15 sextant for sale. It needs new mirrors which are available from Davis for $20.

It fits in a large priority mail flat rate box so I will ship it to anywhere in the U.S. for $20.

Price is $50 plus the $20.00 shipping.

Send me a PM with your email address if interested.
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Old 21-08-2019, 20:13   #9
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Re: Sextant to Learn Navigation Old School

I agree with buying an inexpensive plastic sextant like a Davis as well as you first learn. The romance wears off fairly quickly for a lot of people doing the math old school. My $2,500 sextant makes a great impressive glass cabinet decoration in my man cave where it's lived for many years.
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Old 21-08-2019, 22:21   #10
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Re: Sextant to Learn Navigation Old School

All of the above is good advice*. Personally, I usually use Celestial by Navimatics for most of my almanac data. The USNO website is also a great source for almanac data (and other things). Although, if you want to use a non-electronic alternative (which is certainly understandable), the official Nautical Almanac for the current year is not too expensive and can even be re-used every four years for some time before too much error creeps in (at least for the Sun and stars). Another good program is AstroNav by NavSoft. It generates Almanac pages which look exactly like the official Nautical Almanac for any date between 9999 BC and 9999 AD.



As for sight reduction: take your pick. There are literally dozens of options and almost all will provide accuracy which is reasonable enough. Just remember this basic rule: the more compact/less complicated the table, the less accuracy you can expect - and vice versa [generally]. Although, truthfully, the difference in accuracy matters little. It is also true that the more complicated a sight reduction method is (and the more steps required), the more chances there are for you to make a mistake. Of course, electronic methods usually offer very high accuracy with very little effort - but where's the fun in that? Might as well just use a GPS.


A plastic sextant is certainly good enough to learn with. I would recommend any of the Davis models, including the very inexpensive Mk.3. If you decide you'd like to step up to a metal sextant (which will give you much more consistent results with less fiddling), I would recommend the Astra IIIb by Celestaire. IMHO, it gives you the best "bang for your buck". I would also recommend using an artificial horizon, especially if a sea/lake horizon is not easily accessible. (Note: I mean the type using a tray and a liquid of some sort, not the "bubble" type. The latter is much harder to use successfully.)



Lastly: if you have any specific questions, I'd be more than happy to help. I'd also recommend browsing the archives of NavList. The answer to many questions you may have is probably already in there somewhere. And if it isn't, we'd be happy to help you out.



*I wouldn't personally recommend any app that uses the camera for measurements, though. They're simply not precise enough and they teach you nothing about using a sextant, which is what you will need if you ever want to get measurements precise enough to actually be usable.


I'm also not sure what an "electronic sextant" is.
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Old 21-08-2019, 22:27   #11
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Re: Sextant to Learn Navigation Old School

Quote:
Originally Posted by a64pilot View Post
After you get a sextant, you going to a class, or using a book?
I ask as I need or want to also, I have a used sextant I bought here on the for sale thread.
However it’s my understanding that to teach the basics a plastic one is fine, but as I have no experience myself I can’t say for sure.

I looked into a class and it’s over $300 and didn’t specify how many days it was. Unless it’s several that sounds a little expensive to me.


I’m gearing up to teach a class. I can send you my notes/syllabus if you want.
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Old 22-08-2019, 09:01   #12
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Re: Sextant to Learn Navigation Old School

If you are "Thinking I want to learn celestial navigation" then a plastic sextant is fine.

If you honestly wish to acquire the skill of celestial navigation, I urge you to buy a good metal sextant. Plath, Freirberger, Astra, an old Navy MK III or IV, Tamaya are all good.

Learning celestial is not a few hour task. I would suggest Mary Blewitt's "Celestial Navigation for the Yachtsman" to get you started. You do not need a sextant to get the fundimentals, (although it is more fun), but you will see what is involved and decide if you truly wish to spend the time. It is not hard, but it takes practice. Dutton (I think) said, "you need a thousand sights before you can consider your sites as accurate). As a second officer on a ship I would shoot morning stars (and any planets up), Morning sun around 10, LAN, couple of afternoon sun sights (and the moon if it was up) and evening stars. (I would shoot everything 3 times and average the time and sight to minimize errors) easily 100 sights per day. (given good visibility).

I would also suggest starting by using H.O. 249 (air tables) as they are easy to use although not quite as accurate as 229.
Once you have it down, then I would suggest using phone apps or celestial calculators as you will have a good understanding of what you are doing and can recognize errors better.

Funny, when GPS first came out, I took the first civilian GPS across the Atlantic (Trimble, cost about 25K). It would give a fix for a half an hour or so, at odd hours and times during the day. To learn if it could be trusted I would compare my sights to the GPS fix. I got to where I would use the GPS as my AP and if my intercept was less than a mile, I would simply plot the GPS fix.


Celestial Navigation is an art as well as a science, it is rewarding but it in not something one learns in an hour or two.

Good luck,

M
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Old 22-08-2019, 11:03   #13
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Re: Sextant to Learn Navigation Old School

I second the Davis Mark 25 on which to learn. Look around for a good used metal sextant. I bought a Celestaire Astra IIIb from a seller on CF.

For an instructional book I recommend Celestial Navigation by Tom Cunliffe.

For an inspirational book I recommend Sextant by David Barrie

Start by doing sun sights (noon sight and sun-run-sun) They are easier and in an emergency all you really need.

I had a couple of "ah ah" moments when learning celestial.

1) It is based on a Ptolemaic concept of the universe with the Earth at the centre surrounded by a celestial sphere.

2) A sun-run-sun is simply a running fix, a good reason to understand coastal navigation.
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Old 22-08-2019, 14:42   #14
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Re: Sextant to Learn Navigation Old School

Good for you for being interested. I strongly recommend a book called "A Star to Steer Her By." Combination textbook and workbook with excellent forms. The Davis models are great to learn on and, I regret, many excellent metal models are coming on the market as fewer learn...
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Old 22-08-2019, 19:58   #15
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Re: Sextant to Learn Navigation Old School

I’m a professional captain and basic navigation skills using a sextant is a critical part of be a professional and safe captain for your crew safety should be foremost in your responsibility if other means of safe navigating is not available.
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