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Old 08-03-2008, 02:57   #16
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Sextants aren't just for celestial. Does anyone here use HSAs or VSAs?
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Old 08-03-2008, 03:06   #17
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Quote:
Originally Posted by SkiprJohn View Post
"American Practical Navigator" Bowditch is a very good source on how to tune up and use your sextant. I would check it out of the public library or look for one at a used book store.
Or online - Bowditch Online - chap 16 for sextant use.
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Old 08-03-2008, 05:39   #18
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One of my all time favorite books on navigation by David Burch is called EMERGENCY NAVIGATION - How to find our where you are and get where you want to go without compass, sextant or electronic instruments. This is the book you need when all else fails.

I have read this book dozens of times. It shows you how to use the sun to get your directions and even discusses how early navigators used a kamal to do latitude navigation.

The early dhow navigators simply had a stick and a string with knots tied in the string attached to the wooden stick. Each knot in the string represented the latitude of a different destination. They would simply put the appropriate knot in their front teeth, and hold the attached stick out in front of them. The length of the string determined how much of an arc the stick would subtend on the horizon. Each night they would use their stick and string to arrive at the desired latitude. They simply put the bottom of the stick on the horizon, and then they sailed north or south until the top of the stick exactly touched the north star. Since the height of the north star above the horizon is approximately their latitude, they usually arrived safely at their destination.

David Burch's book is a good read, and it gives a person plenty of tools to use if they ever lose their GPS.
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Old 08-03-2008, 06:02   #19
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Besides sailing and working on boats (specifically MY boat), astronomy is my other great passion (cycling is a distant third ...). As such, celestial navigation has always interested me. Years ago, when I was a kid I helped my father take sights for a Power Squadron course - just taking and recording time, mind you -- but it intrigued me nonetheless. Recently, my dad (now 80) gave me his Kelvin Hughes sextant. Shamefully, I still do not know how to do it. I understand the concept, but have failed to get motivated to practice. About a year or two ago I bought "Celestial Navigation in a Nutshell" - it seems like a really good, clear guide, but I am a lazy bum and need to dig into it.

For me, it would be as much as anything the satisfaction of knowing that I understand this mathematically elegant system of navigation. Of course, on the off chance I would ever need it, all the better ...
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Old 08-03-2008, 09:13   #20
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Yes

Mitch,

I still use a sextant for morning, afternoon and evening fixes while at sea, until visual fixes can be used. I use a GPS for some planning and information, and leave it on when in unfamiliar harbors, but don't use it for primary navigation info.

I find the extra time for the celestial nav is worth being in touch with something so forgotten; it's not like you have much to do at sea anyway.

Introduction to Nautical Science has a lot of good information on nautical studies, and a clear, concise, easy to understand section on basic celestial nav.

Introduction to Nautical Science

Fair fixes and clear skies,
Aaron N.
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Old 08-03-2008, 10:43   #21
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At Cal Maritime we were given vintage WW2 sextants for the students who could not afford to buy their own sextants. The optics absolutely stunk and it did make a difference in the accuracy of our fixes. High quality metal sextants have actually fallen in price since the early 80's. I was pricing some out on the internet and was surprised to see some pretty high quality ones selling for under $1000
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Old 08-03-2008, 11:46   #22
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Yep. And you can find some excellent used ones for even less. Expect to pay $600-800 for IMHO the best: a C. Plath micrometer sextant of late 60's or later vintage (the Cassens and Plath sextants are of approx. equal quality). You can find excellent Tamayas, Simex, etc. for even less. And even the Chinese Aires is a damned good sextant.

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Old 08-03-2008, 11:59   #23
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I have thought about learning to use a Sextant, what puts me off is "the Maths" (note the "s" ) - but then again once the OCD gets properly targetted it's amazing what can be achieved........and Celestial Navigation sounds the perfect thing to cut down my time spent (wasted?!) on the Internet

The main reason for learning would be so I could annoy folk, mainly on the Internet
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Old 08-03-2008, 12:38   #24
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Bill makes a good point about the good old sextants and the price for the best but I traveled across the Pacific using a Davis Mark 25 plastic sextant and could not have been any happier with the results. You can find a good used one for about $125-$150 and they work every bit as good as the higher priced units. For practice you can't beat a Mark 15 ($100) or Mark 25 and they will survive a drop on the deck. Metal ones usually don't.
I currently have a Chinese Astra IIIb which does very well and is in the $300-$450 range.
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Old 26-03-2009, 10:23   #25
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if you have a boat, and actually venture out beyond the sight of land, try this on for size, it's worth a six pack of laughs.
traveling along, beautiful day, take the chartplotter and shut it off, (pull the fuse or whatever), then bag the compass so you can't see it. Then make sure no-one is hiding a handheld GPS receiver and jump up suddenly and yell, "The electronics are out! OMG, where are we?"

Then pull out the charts, say something really profound like, "I think we're here somewhere!" and swing your hand around in a BIG arc across the chart. It will certainly make for an interesting day. Then if you know enough, take out your sextant, the plotting sheets, the clock, the almanac and prepare to meet your match. After you have deduced your position as best you can from the sights and math, turn things back on and show everyone how profecient you are as a true captain of your vessel.
Or, open another beer and tell everyone, "I guess I need to take that classon navigatin huh?"
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Old 28-07-2009, 19:43   #26
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Knuckles at night...

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Originally Posted by Lodesman View Post
Sextants aren't just for celestial. Does anyone here use HSAs or VSAs?
All the time ~ once I get back aboard.. And on dark nights: 2 knuckles come in handy for a quick check.
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Old 29-07-2009, 03:24   #27
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... And on dark nights: 2 knuckles come in handy for a quick check.
See Mitchell Charity's excellent pages on approximation
Your Body Ruler - A User's Manual

Your Body Ruler - A User's Manual

Measuring Angle and Distance with your Thumb
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Old 29-07-2009, 04:21   #28
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We just lost another boat in OZ, due to GPS only. Same trip, same coords for over 6 mths. I don't condemn GPS but I don't rely on it either. We've been here before, on the forum, and hopefully again there'll be positive input. We need backup be it satelite, sextant, orientation with stars and planets or basic nav like look outside and see where the f...... you are going. Our coastline ( Far North Queeensland Australia) doesnt comply with digital technology.
Please excuse me if I spelt fusck wrong.
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Old 29-07-2009, 06:56   #29
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I am able to take fairly accurate noon sites, however, my plastic learners model is really not up to more sofisticated (sp) reading. It is fun working with it though.
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Old 29-07-2009, 07:48   #30
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I purchased one of the plastic ones years ago and learned to do noon sights but took it no farther. I'm mostly a coastal/islands cruiser so it was mostly just as a curiosity. My experience was the same as Dave on MaxingOut said. I could consistently get my latitude within a mile or so, but longitude was a different story all together.
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