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#280501 - 04/29/16 07:51 PM Found an interesting new thing to learn...
haertig Offline
Pooh-Bah

Registered: 03/13/05
Posts: 2322
Loc: Colorado
... Celestial Navigation

I'm studying it, online course materials, with the help of a friend who is experienced with it.

Probably not too much practical use for me, since I've never done an ocean voyage of any kind, much less tried to navigate one (they probably all use GPS now anyways, with Cel Nav only as a backup).

Still, it's fun to learn! Exercise the brain learning new stuff.

Now, I just need to find myself a Sextant Shop. Those seem pretty rare here in Colorado...

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#280502 - 04/29/16 08:22 PM Re: Found an interesting new thing to learn... [Re: haertig]
Russ Offline
Geezer

Registered: 06/02/06
Posts: 5357
Loc: SOCAL
For your purpose, the Davis Mark 3 Marine Sextant is a good option. I've got one and it works well, good for training.

Since you're in CO, you can make an artificial horizon with a dish of water. Works really well for backyard practice.

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#280505 - 04/30/16 07:08 AM Re: Found an interesting new thing to learn... [Re: haertig]
M_a_x Offline
Veteran

Registered: 08/16/02
Posts: 1203
Loc: Germany
I did the same a few years ago (also with no real use for it). This is what I used:
http://www.amazon.com/Sextants-Cardboard...xtant+cardboard

There is also an artificial horizon kit for it. That is basically a spirit level and a mirror.
_________________________
If it isnīt broken, it doesnīt have enough features yet.

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#280506 - 04/30/16 12:49 PM Re: Found an interesting new thing to learn... [Re: M_a_x]
Russ Offline
Geezer

Registered: 06/02/06
Posts: 5357
Loc: SOCAL
Cardboard sextants are a neat idea for an educational purpose, but you could never use one for real, I seriously doubt it can get wet and continue working.

I bought the Davis Mark 3 after seeing it mentioned as part of the navigation package on a sloop preparing for the San Francisco to Hawaii Trans-Pac race. It is accurate to about 2 minutes of arc and is built for actual use. The sun shades are remarkably good, turning the sun into a little orange ball you can sight. Davis Mark 3 users manual

Another place to shop for Marine Navigation supplies is Landfall Navigation. Sextants there run from the Cardboard Sextant Kit to the Cassens & Plath Horizon Ultra Marine Sextant ("accuracy guaranteed to 9 seconds of arc") for only $1795.00 ... Lots of other good stuff too.

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#280507 - 04/30/16 02:44 PM Re: Found an interesting new thing to learn... [Re: Russ]
M_a_x Offline
Veteran

Registered: 08/16/02
Posts: 1203
Loc: Germany
You are right. The cardboard sextant cannot get wet. Assembling it might provide some additional learning experience.
For the original poster it might be an option.
_________________________
If it isnīt broken, it doesnīt have enough features yet.

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#280509 - 04/30/16 09:51 PM Re: Found an interesting new thing to learn... [Re: M_a_x]
haertig Offline
Pooh-Bah

Registered: 03/13/05
Posts: 2322
Loc: Colorado
My friend that is helping me has a sextant. I'm not sure the brand/model, but it is a decent quality metal one, it cost about $650-ish I think he said (or was it $850-ish?). More expensive than I'm willing to pay for just learning this for fun. I doubt I will ever truly "navigate" with a sextant, books and charts, I'll just learn the skills required and practice for fun. Even though he said he'll help me using his sextant, I may buy a less expensive plastic one for my own practice when he's not around. Who knows though, I may end up buying a nice metal one. I like owning and admiring high quality well made precision things, whatever they may be!

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#280512 - 05/01/16 12:18 AM Re: Found an interesting new thing to learn... [Re: haertig]
Russ Offline
Geezer

Registered: 06/02/06
Posts: 5357
Loc: SOCAL
I thought about getting one of the high end metal sextants, but the "Davis Mark 15 and Mark 25 sextants have three scales that give readings to 2 / 10 of a minute" of arc -- an order of magnitude better than the Mark 3's 2 minutes of arc and IMO plenty accurate for most marine navigation.

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#280513 - 05/01/16 03:27 AM Re: Found an interesting new thing to learn... [Re: Russ]
haertig Offline
Pooh-Bah

Registered: 03/13/05
Posts: 2322
Loc: Colorado
A sextant would obviously have to be accurate, but I don't know what level of precision is needed for ocean navigation, or how precise sextants can actually get. But I imagine there's a point of diminishing return spending more money to get more precision. For example, I have a watch (analog now, with my aging eyes!) that has a second hand. That's all the precision I need. And I don't even look at the second hand during daily chores! A watch with a 1/10 second hand would be 10x as precise, but probably no more accurate, and certainly no more useful than my cheaper watch.

For my uses, which are to simply learn the concepts and techniques of Cel Nav but not actually use it for real navigation, I'm sure I could get by with an inexpensive sextant. A very inexpensive one. But I'm also looking forward to using my friends, under his guiding hand, so I can learn the finer points of sextant use like the drum and vernier scale that will give you higher precision.

Time will tell if I can get my fill of the finer points with my friends sextant and then opt for something like the Mark 3. Or if I'll want to step up (relatively speaking) and get a Mark 15. Or if I get enthralled by the fine mechanics and end up buying a metal one, which would mostly be for display and admiring in my home.

But I'm just at the very beginning of all this. I've read the theory parts of Blewitt's book "Celestial Navigation For Yachtsmen" and I've gotten a few chapters into Burch's book "Celestial Navigation".

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#280514 - 05/01/16 04:01 AM Re: Found an interesting new thing to learn... [Re: haertig]
Bingley Offline
Veteran

Registered: 02/27/08
Posts: 1576
From what Russ is saying, it seems the cardboard sextant would be quite sufficient for your course in the great maritime hub of Colorado. Save the money for something else, like a GPS.

On the other hand, if you want to have something to show off to friends -- and I suspect this may be the case, because even I want such a thing -- then perhaps Russ (or another seasoned seadog) can recommend something with that in mind. It's gotta be decent enough for learning, and it should look good next to a musket and a triangle hat. smile Come on, just admit it!


Edited by Bingley (05/01/16 04:01 AM)

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#280515 - 05/01/16 05:00 AM Re: Found an interesting new thing to learn... [Re: haertig]
haertig Offline
Pooh-Bah

Registered: 03/13/05
Posts: 2322
Loc: Colorado
From what I understand thus far (or what I think I understand!), the lions share of the work in celestial navigation is not in taking the sights, it's everything else before and after that. Working with the sight data, times, tables, charts, a little basic math, etc. So yes, I'm sure I could get by with even a cardboard sextant. But admit it, putting that up for display on the living room shelf is going to be a tad on the cheesy side. I guess you could put it up next to the telescope you made from a wrapping paper tube.

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