What sextant ?

Sven

Seglare
It is time to re-learn how to use a sextant. Having only spent an afternoon with a sextant and some hands on training 40 years ago I'm basically completely ignorant. I guess good books on the topic wouldn't be a bad idea either.

What sextant should we be looking at if we want to use the same one to re-learn and to use for the next 20 years ? Yes, we'll of course have GPS equipment too, but GPS use depends on others too much.

Thanks,


-Sven
 
Sextant

Sven,

I live on the western coast of Florida, and about 25 years ago a friend gave me a Davis Instruments plastic sextant. They came in a couple of grades back then, and I believe that the one I was given was the better or the two.

I had read Wm. Buckley's "Atlantic High" wherein he made much of the efficacy of knowing how to use a sextant. He made it sound easy. I found out that it was anything but. I bought the requisite books (H.O. 229 and some others). I got some pads whereon one could enter the calculations in proper sequence. This "learning" process went on somewhat endlessly over several months. The errors I made were laughably stupid. Finally, I got out on the beach here, pointed my sextant at the sun, got it down to the horizon and recorded the precise time. My watch was coordinated with Naval Observatory Time. Of course, I knew exactly where I was when I took that sight.

Then I went home and worked out an LOP. No matter how much I tried, the best I could do was to get an LOP that was 30 miles from where I knew I had been when I took the sight. The next day I went down to my marine equipment store and bought a Loran C. I knew in my heart of hearts that there were some things I was never going to be able to do. Finding out where I was with a sextant was tops on that list. Still is.

The Loran has given way to a GPS. I started small. I have jumped up a couple of notches since. I have a hard-wired Garmin on board my E-27. And I have a couple of other Garmin 478s, which are light years ahead of the hard-wired unit.

Point of fact, the technology today obviates sextant use, in my opinion. The information you get from a GPS unit is accurate, timely and a cinch to acquire. With all the other ancillary information you also get--SOG, ETA, ETE, waypoints, courses to follow--there seems to be no reason to bother with all the complexities that the use of a sextant entail. I say this because I believe it and because I miserably failed to acquire the skills necessary to operate a sextant with any degree of accuracy. But I tried.

As a strange aside, I used to live in New Hampshire, in a small town in the southwestern part of the state. It was called Fitzwilliam, a Currier & Ives type of village with nearby granite quarries and a latticeworks of stone walls at every house. The house I lived in--a lovely manse owned by my stepfather--had open-beamed ceilings, fireplaces upstairs and down, five bedrooms, a tennis court, and lovely amenities throughout. My stepfather, a retired executive from Pacific Mills, later Burlington Industries, bought the house from a family from Salem, Massachusetts. This had been a summer retreat for them. The former owners' name was Bowditch...as in Nathaniel Bowditch.

Good luck. I never had much.

Morgan Stinemetz
 

Sven

Seglare
Hi Morgan,

Sven,

I live on the western coast of Florida, and about 25 years ago a friend gave me a Davis Instruments plastic sextant. They came in a couple of grades back then, and I believe that the one I was given was the better or the two.

I had read Wm. Buckley's "Atlantic High" wherein he made much of the efficacy of knowing how to use a sextant.
I suppose pointing out how he got politically lost would be inappropriate ? BTW, I was a fan of his back then.


family from Salem, Massachusetts. This had been a summer retreat for them. The former owners' name was Bowditch...as in Nathaniel Bowditch.
fascinating and small world.
Good luck. I never had much.
Thanks, Maybe the plastic was part of the problem ? Even 30 miles would be better than nothing if GPS gets turned off. The theoretical accuracy isn't that bad, but it is theory ... from Wikipedia:

Professional sextants use a click-stop degree measure and a worm adjustment that reads to a minute, 1/60 of a degree. Most sextants also include a vernier on the worm dial that reads to 0.2 minute. Since 1 minute of error is about a nautical mile, the best possible accuracy of celestial navigation is about 0.1 nautical miles (200 m). At sea, results within several nautical miles, well within visual range, are acceptable. A highly-skilled and experienced navigator can determine position to an accuracy of about 0.25-nautical-mile (460 m).[1]
Thanks again,


-Sven
 

Guy Stevens

Moderator
Moderator
Thermo Plastics

Thermo Plastic sextants are very sustible to thremal distortion.... Most people Even those that are very good at celestial navigation try to avoid using them.

A good metal sextant is an amazing instrument....


Yes almost all of the time the sextant is superseded by GPS, however sometime I may have to tell the story of the 4 of them that broke on a single crossing. I soldered one of the boards in one of the units back together in 15-18 foot beam seas sitting on the sole of the cabin. However I wasn't too worried, because I did have an Astra IIIb and my tables and almanac available.... (it is hard to take sights in those situations too....)

GPS is what made it so that droves of people could actually go cruising. It took a lot of the mystery and fear out of ocean passages for a lot of people. But long before then people lots of them, did ply the oceans with only the trusty sextant, Chronometer, almanac, and tables.....

Belt and suspenders never hurt anyone.... Transoceanic passages I always take it..... IF the government of the US turns off the GPS, then I can still figure out where I am going.....

Guy
:)
 
Sextants redux

Guy,

To each his own, skipper. Anyone who can solder GPS units back together is a better man than I. Probably knows how to make a sextant work, too. I( just cannot do it. What is more, I know it.

Morgan Stinemetz
 

CaptDan

Member III
Guy,

To each his own, skipper. Anyone who can solder GPS units back together is a better man than I. Probably knows how to make a sextant work, too. I( just cannot do it. What is more, I know it.

Morgan Stinemetz
This year, after nearly twenty years on the water, I decided it was time to teach myself some basic cel nav. After reading 'My Old Man And The Sea,' I got the bug, I guess. So, I picked up a couple of books and bookmarked several online study/discussion sites.

Then I picked up a 1941 US Navy MKII sextant on eBay. There were literally thousands of these made during WWII - by companies under contract to the BUships - David White, Pioneer Eclipse, Bendix, etc. Fortunately I found one with two scopes and all filters and mirrors intact for $160. After cleaning it up and having it checked out for accuracy by the wizards at Captains Nautical in Seattle, I set about learning to shoot a basic noon sight.

Now, up here in Latitude 48, El Sol is rather rare bird, but around July 5 it begins to appear. So I headed down to the boat, and while tied to the pier, shot a bunch of sights (latitude only) and reduced 'em. The first two reductions put me around Victoria BC, 71 miles from my position, checked against the GPS. The next three were more promising - with a much smaller circle between Whidbey Island and Federal way - still too inaccurate to navigate by.

The problem wasn't the sextant, my math or the sun; it was the horizon. You MUST have a good, visible horizon, sufficient distance from your sighting position, or you might as well forget the whole thing.

So, the point of my rant is, it takes a LOT of practice, a good steady hand (imagine shooting a sight from the bucking deck of your yacht in a blow), accurate tables, a visible horizon and a lot of dedication. But, even if you end up sucking at cel nav, you'll develop a HUGE appreciation for those who can do it well.

I say go for it; learn as much about it as you're willing. Whether you actually use it on passages, well - I can't really say. But it's a facinating subject.

YMMV.

Capt Dan G>E35II "Kunu"
 
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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
"and a star to steer by..."

I was given a Davis plastic sextant about a decade ago. Never tried to use it, and probably never will.
If I ever do the "Hawaii circle route", I will probably be another sailor following jet contrails... while looking down at the GPS for making regular log entries...
:rolleyes:

Maybe Sven should email me off-list...............

Loren
 
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Sextants again

Dan,

I have the utmost respect for people who can do things that I cannot. There are different skill sets involved than the ones I came equipped with or developed. I was a good sailboat racer at the club level, though I do not do it anymore. However, I raced for 30 years and had far, far more podium finishes than not. But about 18 months ago I raced with three others on my boat who were head and shoulders above my capabilities. We won our class by 6:24 in actual time, and we were one of the slowest rated boats in the class. It showed me that I had been playing on the kiddie playground for a long time.

I follow some of the threads on this site with muted amazement. There are people talking cogently about aspects of sailboat technology I have never even heard of. I understand sails and trim, but when it comes to real technical stuff, I am just left bobbing in the wake. I'm impatient by nature and don't have the chops to wiggle my way into what appears to me to be the unending underground cavern of celestial navigation. I would if I could, but I can't. I discovered my limitations, and, to tell the truth, it came as a bit of relief.

Best regards,

Morgan
 

Guy Stevens

Moderator
Moderator
Horizon

CaptDan,

For shooting inland with a hand held sextant you need an artificial horizon.

Davis used to make a nice one.

Still does for apparently $22.95

http://www.landfallnavigation.com/-nd144.html

I started learning with one of these. It forces some limitations on your sights, but it also teaches you a lot. If you have a sextant I would highly recommend this.

The best book ever written on the subject....And I hate to mention it, cause it is the book I teach out of, and it is out of print it is by John Budlong called "Sky and Sextant" far far far better than any of the rest, and I have tried to use the all in my classes. You can find a copy in some of the used book sites.

Using this book, an artificial horizon, and a few classes where someone that knows how to shoot is looking over their shoulder, I have not had a student yet that wasn't able to shoot a sight... Do a reduction on the back of an envelope Plot their LOPS and determine their position with reasonable accuracy.

If Morgan Stinemetz ever comes to the area, I would be happy to help him shoot his position with some accuracy in about 2 days. Let me know Morgan I would be happy to help if you would like to do it. (You have to get your own copy of the book though! :) )


Guy
:)
 
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Lucky Dog

Member III
Anyone can do the easything

Three cheers for anyone willing to travel the roads less traveled. I have been sailing since I was toddler. Every boat my family owned was less than 20 feet long. All restored wrecks. Only day I ditch in high school was to continue working on a 19 foot mahogany Arrow, principal let me off with a smile and said wish he could have been there to help. I now have a 53-year-old Oldtown canoe and Thomas brothers Whitehall. Our 35Iiwas a great deal but needs work.

My rants point is that I paddle, row and sail not because it is the fastest way of what everybody else is doing. If given the opportunity to afford a new sailboat, I am not sure I take it. Their many more efficient sail rigs than ours. How many time have guests on your boat said, why do you need all these ropes, how do know which one to pull, wouldn’t a motorboat be easier. I always smile and gently offer, that is not why a sail. There is a persona satisfaction to “do it myself”, to work with nature using a high technical sailing rig that has direct tie to the history of this worlds exploration.

We should share our passions of sailing with others and learn as much as we can about how got here.

To add to the mix, here is a link to make your own sextant. My advisor in sea explores, a very long time ago taught us how to use a sextant and make a simple one that was and still is in the manual.

http://www.geocities.com/richardandtracy/sextantpage1.htm

ml

ps, I have three gps,s just in case
 

Lew Decker

Member III
:):):)Hi Sven -

As you know, I hit a reef and lost everything I owned. I am the last person on the planet to wade around in these shallow waters. However...

Using a sextant is more a physical challenge than mental. Bringing a star down to the horizon in 8' seas from the deck of a small boat requires some dexterity that a lot of people never quite master. This may sound stupid, but if you have a good sense of rhythm it is not hard to do. Timing is the key.

I had a huge advantage with Sun Flower. She was so stable that I could stand on the deck, bring the star down to the horizon, and wait for the time ticks on WWV to buzz the minute.:egrin: --- Chronometer? I had a great one but I never used it.

If you are in the market for a sextant, I think I would opt for a few essentials.

1) Good optics with some magnification. I used a Tamaya with a 7X scope. What you are looking for here is light gathering ability without so much magnification that your movements are exaggerated. I used a sextant on a trans-Atlantic jaunt that had no magnification. That thing was a pain in the arse. The owner of the boat insisted on being the navigator. He missed Bermuda by 25 miles and had to call a passing freighter for help. 'Nuff said.

2) Heavier sextants are easier to use than than the lightweight Davis instruments. Something about stability here. There is also something to be said for 'precision equipment'. I like cool toys that reek with quality, like something we could have bought at the old Abercrombie and Fitch store before they lost their way and became a cliche' for Madison Avenue clothing chains.

3) The mirrors and light filters need to be as good as the optics. On my Tamaya - after years of hard use - the silvering on the mirrors began to erode. It didn't affect the accuracy or ease of use, but it would have become an issue.

As for GPS, it is magic, pure and simple. If I were to wander off to sea, I'd have several on board including one in a sealed, waterproof container just in case. But...For pure, unadulterated romance of the sea, I'd also have a sextant;). I'd use it, too.

I know, I know...But it was cloudy and rainy all day long and we had sailed 170 miles in 17 hours. I was never able to get a sight on anything. I hit the reef fair and square, but it wasn't because of my sextant:rolleyes::rolleyes::rolleyes: ...
 

Sven

Seglare
Guy,

...
The best book ever written on the subject....And I hate to mention it, cause it is the book I teach out of, and it is out of print it is by John Budlong called "Sky and Sextant" far far far better than any of the rest, and I have tried to use the all in my classes. You can find a copy in some of the used book sites.
...
There were 7 used copies via Amazon resellers, now there are 6. At about $15 plus shipping it was worth gambling on your advice :)

Thanks,


-Sven
 

Sven

Seglare
Hi Lew,

It was good seeing you again on Friday.

...
I know, I know...But it was cloudy and rainy all day long and we had sailed 170 miles in 17 hours. I was never able to get a sight on anything. I hit the reef fair and square, but it wasn't because of my sextant
...
Your shipwreck story sure is depressing :-(

The Tamaya sextants are pricey, but probably for good reason.

Thanks for that lead too.


-Sven
 

Emerald

Moderator
[snip]
For shooting inland with a hand held sextant you need an artificial horizon.

Davis used to make a nice one.

Still does for apparently $22.95

http://www.landfallnavigation.com/-nd144.html

I started learning with one of these. It forces some limitations on your sights, but it also teaches you a lot. If you have a sextant I would highly recommend this.

[snip]

Guy
:)

Hmmm, I picked up a WWII vintage RAF bubble compass not quite knowing what it was, but thinking it was a nice vintage instrument and the price was peanuts and maybe I could use it on Emerald, so I dragged it home. Did some research and learned it was for use in planes and had an aritificial horizon (bubble part). Figured I had struck out for the boat, but now wondering if I've got a good learning tool while I keep my eyes open for a marine sextant. Meanwhile, I am far enough up the Chesapeak that knowing how to use one is pretty esoteric, but I still feel like I should know how in theory, even if I find I can't get good enough to be accurate. I hope to do some offshore sailing, and figure I should know how to do it well enough to get in the ball park of where I am in case nothing else works.
 
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mherrcat

Contributing Partner
When I was in London a few years ago installing some satellite earth stations I was looking at sextants in a local chandlery and realized that with the artificial horizon they could be used to verify look angles. Set the satellite elevation on the sextant arc, point yourself to the correct azimuth using a compass, take a sighting and if you're looking at a tree or the side of a building, you need to move the satellite dish...
 

CaptDan

Member III
CaptDan,

For shooting inland with a hand held sextant you need an artificial horizon.

Davis used to make a nice one.

Still does for apparently $22.95

http://www.landfallnavigation.com/-nd144.html

I started learning with one of these. It forces some limitations on your sights, but it also teaches you a lot. If you have a sextant I would highly recommend this.

The best book ever written on the subject....And I hate to mention it, cause it is the book I teach out of, and it is out of print it is by John Budlong called "Sky and Sextant" far far far better than any of the rest, and I have tried to use the all in my classes. You can find a copy in some of the used book sites.

Using this book, an artificial horizon, and a few classes where someone that knows how to shoot is looking over their shoulder, I have not had a student yet that wasn't able to shoot a sight... Do a reduction on the back of an envelope Plot their LOPS and determine their position with reasonable accuracy.

If Morgan Stinemetz ever comes to the area, I would be happy to help him shoot his position with some accuracy in about 2 days. Let me know Morgan I would be happy to help if you would like to do it. (You have to get your own copy of the book though! :) )


Guy
:)
Yeah, I've been thinking about getting an artificial horizon for months now. But, sometimes, that's how long it takes for the sun to appear up here.:egrin:

Thanks for the book recommendation. I've been studying out of Blewitt's 'Cel Nav For Yachtsmen' - an okay primmer but a little 'arcane.' Bauer's'excellent 'The Sextant' has been very helpful in many technical and maintanence areas. Believe it or not, Davis' manual for their MK25 sextant is pretty informative for doing basic noon sights.

All in all, I 'get' a lot of the theory, the reduction methodology, instrument corrections and 'rocking' technique. But there are plenty of 'holes' in my comprehension and practice which I hope to close up eventually. You're right - having a mentor to look over one's shoulder is really the way to go.
Too bad I don't live in Bay Area anymore, I'd be knocking on your companionway.:nerd:

Capt Dan G>E35II "Kunu"
 

CaptDan

Member III
:):):)Hi Sven -

1) Good optics with some magnification. I used a Tamaya with a 7X scope. ...
No doubt the Tamayas, Plaths, Cassens & Plath, Friebergers, and even the older Russion SNO-T/M series (Plath clones) - with their larger mirrors,superior optics and frame heft, are supposedly better than the cheaper plastic variety. However, many expert navigators sing the praises of the relatively inexpensive Astra IVb, a Chinese instrument (and among the few companies still making sextants), with aluminum frame and decent quality.

That said, the olde Navy MKII ain't bad either - assuming you find one in unmolested condition with its Correction Sheet still intact. Thousands of successful sights were done with these. However, their small mirrors make star sights difficult on small boats (after all they were generally used on large ships.) But if all you're doing is noon sights, you really don't need extensive magnification or large horizon/index mirrors.

But what do I know? Everything I've gathered is mostly second hand - like the WWII classic laying in its old wooden box.:rolleyes:

Capt Dan G>E35II "Kunu"
 

Rob Hessenius

Inactive Member
Celestial Navigation in the GPS Age

Hi Guys~

I'm not into navigation with a Sextant and have never even tried to learn, but a gentlemen from my town has written a book about it and has had very good reviews. The book is called Celestial Navigation in the GPS Age, the author is John Karl and the book is available on Amazon. Maybe something that you can try out and enjoy. I can even get you his number if you would like to talk to him. Trust me, he loves to talk on this subject. I have no interest or financial gain in this. I just thought it might be a good read for you.

http://www.amazon.com/review/product/0939837757/ref=dp_top_cm_cr_acr_txt?_encoding=UTF8&showViewpoints=1
 
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Sven

Seglare
...
The best book ever written on the subject....And I hate to mention it, cause it is the book I teach out of, and it is out of print it is by John Budlong called "Sky and Sextant" far far far better than any of the rest, and I have tried to use the all in my classes.
...
I just got my used Amazon copy today and you are right: It looks very well written !

Thanks for the recommendation.


-Sven
 
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