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So, sextants cost HOW MUCH!!

Anyone tried out this simple KISS sextant yet for a bit of fun?  ;)

http://www.tecepe.com.br/nav/CDSextantProject.htm (http://www.tecepe.com.br/nav/CDSextantProject.htm)

There is a Davis plastic sextant on ebay right now.  It'll get you close enough if you ain't laying a minefield... probably go for $25 to $35... Tjim

The Davis plastic sextants are passable as long as you don't leave them in the sun and let them warp...  For most people using them as a navigational backup or for learning, the error in a plastic sextant will be less than the human error from lack of practice and experience anyways...

People often don't realize that celestial navigation is an art as well as a science.  Learning to use an almanac and doing the math to reduce the sights is easy -  the calculations are either right or wrong, and very straightforward once you learn how to do them.  It's the actual physical observation that's the tricky part, and that just takes lots of practice.  Learning to deal with the motion of your ship, the sun poking in and out of the clouds, finding the max altitude at local noon, getting a round of evening stars between when the stars show up and the horizon disappears into dark...  this is where the art comes in.  An old mentor once told me that celestial navigation is exponential - the same increase in accuracy that you see after 10 sights will take you 100 sights to do again, and to make your fixes even more accurate by that same amount will take you 1000 sights.

If celestial nav is something you plan to put the time into learning though, a decent metal sextant is a worthwhile investment.  You don't need a new, several thousand dollar model - a few hundred dollars can get a good quality used sextant if you look around.  You'll appreciate the solid feel as opposed to the flimsy light plastic (steadier when observing) and increased accuracy of the observation itself (better optics, finer tolerances, less wear over time and better dimensional stability).  Once you've used a good sextant it's hard to go back!  (like so many things, isn't it?)    ;)

Quote from: Bill NH on March 17, 2008, 11:29:51 AM

The Davis plastic sextants are passable as long as you don't leave them in the sun and let them warp...  For most people using them as a navigational backup or for learning, the error in a plastic sextant will be less than the human error from lack of practice and experience anyways...

Agreed.  I have a Davis plastic sextant and it has been a great learning tool.  I've gotten numerous dry land sites within 2 miles of a known position.  At sea I need more practice.   ;)

Quote

getting a round of evening stars between when the stars show up and the horizon disappears into dark...

I've read, and have found with my own (admittedly limited) experience that taking star sites is actually far easier in the morning.  Your eyes are night-adapted and you are picking up a bright spot on a dark background (both the star and the horizon), rather than picking up a more-or-less bright spot on a light-but-getting-darker background with light adapted vision. 

Quote

If celestial nav is something you plan to put the time into learning though, a decent metal sextant is a worthwhile investment.

I did not want to poo-poo this CD sextant idea outright, but I am wondering what the accuracy will be - short arc, vernier  with 20' increments, plastic body and mirror mounts...  In short, if the instrument is inaccurate, one just learning might well get discourged.  I've run into that with my plastic Davis.  It is not a bad instrument if you know it's limits and take care to account for them (the biggie is to measure IE for each shot).  But, if you forge ahead without the extra care and get poor readings, you can well assume taking good sights is impossible.

Quote from: Captain Smollett on March 17, 2008, 11:48:04 AM

Quote

If celestial nav is something you plan to put the time into learning though, a decent metal sextant is a worthwhile investment.

I did not want to poo-poo this CD sextant idea outright, but I am wondering what the accuracy will be - short arc, vernier  with 20' increments, plastic body and mirror mounts...  In short, if the instrument is inaccurate, one just learning might well get discourged. 

Hey guys, this sextant (and the octant) were just a couple of things I stumbled across and knowing there are quite a few Sailfar'ers into their celestial navigation, as per the original post I just wondered had "Anyone tried out this simple KISS sextant yet for a bit of fun?"[/color].

Yes, the accuracy is always going to be very much a case of 'thereabouts' rather than 'there', but it would be interesting to know the results if anyone tries it.

Although I'm a bit rusty around the gills, in times past I was a professional navigator so the art of celestial navigation pre gps/sat nav is not alien to me and if you are going to seriously undertake this art then a decent metal sextant is the way to go.

Google the "Bris mini sextant".  It was developed by Sven Yrvind of VERY small boat fame.  It is a simple to build, fixed angle(s) sextant which is so simple, once you see it, you'll want to build a few just for fun.  I bought a pack o 74 microscope slides from Edmund Scientific  for under five dollars and can probably make several dozens of dozens of these mini sextants for that price.  I find that it works very reliably and is a fun idea for just playing with celnav and/or in your ditch kit. Even without taking a day to calibrate it, assuming that you have an almanac (or can approximate the offset from GMT noon passage)you could easily determine LAN from averaging a few before and after noon sights - to get your LAN and longitude - no calibrated device needed. That's cool.

This again is for measuring fixed angles, so you wait until the object you are viewing presents a reflection on the horizon, then HACK! take the time from your watch and work backward through the tables.


Not bad for a few pieces of glass and adhesive.


>RadioRay ..._ ._
s/c Milenka
near Irvington, Virginia - USA

Very Cool, and Welcome to Sail-Far!

Tim

Thank You Tim,

Nice to be here!  I've been a long time reader, and should be posting more. It is enjoyable and a good learning experience to be reading about 'my kind of boats' and especially about those who sail them.

---

An update on the Bris mini-sextant project here.  Per Sven Yrvind's notes, I ordered 'beam splitter glass' from Edmund Scientific.  Making these mini sextants using the beam splitter is a significant improvement in the quality of the reflections seen in the instrument.  My 5x6" piece of this precision beam splitter glass cost roughly $14USD and I can likely make 10-12 sextants from the amount provided. The only significant difference between Mr. Yrvind's original design and mine, is that I've fully enclosed the sides of my unit with epoxy and fiberglass board (printed circuit board material) so that the inner glass surfaces are fully sealed against seawater, dust etc.

I would highly recommend anyone who already enjoys a working knowledge of the basics of celnav and has a horizon to look at, build some of these, either using the very inexpensive microscope slides, or the much nicer beam splitter glass. I could easily see this included in David Burch's "Emergency Navigation" - rev. 2 that just came out. If a sailor is at all handy (and most sailors ARE...) it would be easy to produce very accurate noon sites and more with odd bits of window glass formed into a Bris mini-sextant. This also works for the moon as well.


RadioRay ..._ ._
s/v Milenka
nr. Weems, Virginia - USA

You got me interested enough to look.

Here: http://www.yrvind.com/various.html

you can find the info. At the bottom of the page are two small page pictures which take you to full size ones (scans of an article, I think) with fairly complete instructions. Biggest limitation seems to be that it is for the sun and only the sun, but for the size and cost, that isn't so bad.

Gee, do you think it was called,

Quotethe "Bris mini sextant"

because they clipped the Arc too short?

so where can I buy a sextant is there anything online that sell one. I want to say cheap but that is impossible to find a cheap one to learn on i bet.
so anyone know of websites I can check out?

Chris -

The Davis Mark 3 is what you are looking for. Cheap, functional - some people have actually used them as primaries during their circumnavigations...

Here's one at Defender.com :

http://www.defender.com/product.jsp?path=-1|17|6626&id=83267

(http://www.defender.com/images/803267.jpg)

Thanks i was wondering should I buy an L-cheapo now and then buy a better later or what. I could swing maybe 250 for a metal one but seems like the cheapest I seen was like 572 for a metal one I think it was called a Astra.

Thanks
Chris

Unfortunately, a new metal sextant is going to be expensive.  The plastic Davis ones are great, provided you don't leave them out in the sun and have them warp. :) Good as an emergency sextant too.

Chris,

You've probably already checked out the Celestaire web site:

www.celestaire.com (http://www.celestaire.com)

This company offers a wide variety of new sextants, some of them top-of-the-line.

You might also look on eBay. I've seen some good-looking (haven't bought any), older, used sextants. But on eBay you'll also find a lot of Indian-made "reproduction" instruments that probably look great as cocktail-table ornaments, but won't work under maritime conditions.

You might also check with various instrument companies, such as Robert E. White Instruments,
[url]www.robertwhite.com[/url)]
--but they'll be very expensive. You might want to find an older sextant and get it reconditioned by somebody like White. I assume that most major seaports have such companies. White was in Boston for many years (the mailing address for the internet company is in the southwest suburbs), but I'm sure places like Baltimore, Annapolis, and other places have similar companies.

My own sextant, which I've owned for more than 40 years (and never used at sea, I regret to say) was built in London by Heath and Company in 1904. I mentioned this instrument once to Ridge White, the current owner of Robt. White, and he suggested I not bother to use it at sea--but, darn it, sailors used vernier-gauge sextants for centuries.

The key to using a sextant is practice, practice, practice. Trying to bring a star to the horizon in a small boat must be one of the trickiest aspects of celestial navigation. In fact, I can't imagine trying to do so on my 25-footer.

I bought my Heath sextant after my celestial navigation class while in college. The university was forcing the instructor to retire, and depleting its inventory of teaching instruments. It seemed like a bargain at the time, but it looks like you can find used vernier sextants (much harder to use than modern micrometer instruments) for a few hundred dollars. I paid $125 for my sextant (in 1967 dollars) and found one online for only slightly more than that (in 2005 dollars, of course).

Anyway, good luck.

--Joe

yes I have heard of celestaire that was the website I seen the astra sextant on.

Joe do you know of any good books that teach you about useing a sextant? This sextant here http://www.defender.com/product.jsp?path=-1|17|6626&id=83267 says it comes with a book but usually there is a book out there that goes more into detail your know?

Chris

Chris,

There are a number of textbooks with worksheets out there, and there is at least one UK-based company that offers highly regarded online courses in celestial navigation.

I just looked up the book that I have, and a rewritten version is still available here for under $11 bucks:

http://www.mdnautical.com/cmcn.htm (http://www.mdnautical.com/cmcn.htm)

This was the course written by my navigation teacher, the late Frances W. Wright, in 1969 and revised in 1982. There are certainly many more courses out there. Celestaire sells a bunch and there is that British website. (I thought I had bookmarked it, but apparently not.)

I think the US Power Squadron gives courses in celestial navigation, too.

The most important thing is to practice. There are navigational computers, roughly the size of pocket calculators, that can do all the math for you, but it still makes sense to learn how to do the math, which isn't all that difficult if you have an almanac and the right forms.

But sextant use is--if I remember correctly--as much an art as a science. I haven't practiced it in years.

I'm sure there are people on this board with REAL experience at celestial navigation, and they can probably give you better leads.

Once again, best of luck in your quest.

--Joe

There are always sextants available on ebay...I bought my Davis there.

And don't let anyone tell you these plastic sextants are just toys or only good as a backup or just for learning. I routinely get my position to within 1 Nm or less. I wouldn't bother buying an expensive metal sextant.

Thanks guys I'll have to order this plastic one for sure then

Get a plastic sextant to start learning.  However, know that the optics are c**p and they are dimensionally unstable.  MrBill, if you're consistently within 1 nm with a Davis I'm very impressed.  On a moving small boat that's hard with any instrument.

We use the Davis Mk15 and MK 25 as teaching sextants because they get used (and abused) by many students.  They are the better of the plastic sextants.  The MK3 is a practice or backup sextant, period.  Far inferior to even the MK15 and MK25.   

With sextants, as with many things in this world, you get what you pay for.  For yacht use I'd highly recommend the Tamaya Venus model.  It's 7/8 size and correspondingly lighter.  The smaller size stows easily and the weight is good on a moving boat.  I used to own one and wish I still had it - I sold it when I switched to commercial ships from schooner sailing...

The one I kept is a C. Plath (Hamburg,1960s) with both a high power scope for the sun and a lesser magnification star scope.  On a bigger, more stable vessel it can't be beat.  With the sun scope its like setting a basketball on the horizon!  I did use it on a delivery to the Marquesas and Tahiti on a 38 footer (without electronics), but my preference would be for the Tamaya Venus for SailFar size boats.  Another good 7/8 sextant is the Frieberger Yacht Sextant (also German) which is a bit less expensive. 

Both of these come available on eBay periodically.  However, make sure you have the option to have it checked out and return it if it is other than as advertised.  I can highly recommend Robert E. White in Boston for sextant sales and service, ask for Ridge White if you call.  I've both bought sextants and had them maintained by them.  Incredible personal service.  They also stock used sextants that they have gone through and made sure are in proper adjustment.

But back to the original question.  Get any sextant and start practicing.  Celestial navigation is both a science and an art.  The science is in the calculations, but the art is in using the sextant itself.  Calculations are either done correctly or not, and once you learn how to do them you can't get any better at it.  However, the learning curve is in actually using the sextant.  Fortunately you can improve rapidly at first, but it takes progressively more and more shots to continue to improve.  One of my early mentors once told me that the improvement I'd seen in my first 10 sights would take another 100 sights to replicate, and to do the same again would take 1000.  I'm not sure if its that extreme, but the message is that you can get passably good pretty easily, but it will take lots of time and practice to get really good. 

So get something and get out and start learning.  When you're ready for an expensive metal sextant you'll know it, just like a beginner taking guitar lessons who eventually realizes that he wants a better guitar.  Meanwhile, you haven't tied up your cash in an expensive instrument until you need to.

Wasn't it one of these that Tania Aebi used to start with because it looked less intimidating then discovered it was warped and that's why she couldn't get consistent readings or even readings that made sense?  Once she switched to the more complex looking better sextant things started working just gine.

Quote from: Joe Pyrat on December 23, 2008, 09:53:53 AM
Wasn't it one of these that Tania Aebi used to start with because it looked less intimidating then discovered it was warped and that's why she couldn't get consistent readings or even readings that made sense?  Once she switched to the more complex looking better sextant things started working just gine.

Yeah she had a warped one she got used (i think it was the one her dad used on their previous atlantic crossing), I don't think it was less intimidating... just free/cheap.

I also think her book is what started the whole fear and rumors of plastic sextants. They are precise enough for navigating a small boat as long as they are not warped... the only way to warp them is to leave them sitting out in the sun (or other heat sources). Other than that you can damage them in any of the same ways you can damage a metal one.

And just as a side note: Tania had taken an online course and pretty much failed it... Her father had taken a class and she had his books from it...she understood the math, but had never used a sextant on a boat before leaving NY. She managed to navigate all the way to the pacific using DR and getting positions from passing ships, and occasionally using her Radio beacon locator thing.
Finally somebody pointed out the problem with the sextant and she got a new one (used) and was then able to become confident with her skills.

Not that I recommend navigating by DR and radio only  :)  I just think that shows how much people over-think everything instead of just getting out there and doing it like tania did. I think what makes a person a good sailor is their ability to improvise and adapt to whatever is thrown at them, it has nothing to do with being an expert at anything before you leave. Tania is a perfect example of this, she had every intention of navigating by sextant, but she also had never used one at sea before... she made due with what she had at the time, and the rest is history.

Actually, IIRC, she left it out in the sun and the heat of lying in the sun allowed it to warp.  That's what I believe it said in her book, Maiden Voyage.  She got an old Frieberger sextant after that, and that worked just fine.

Seems like I remember her RDF being an old transistor radio.  She had no idea where she was on her way to Bermuda but was able to tune in a Bermuda radio station and would just sweeping the horizon with the radio until the signal peaked and sailed in that direction.  She was lucky, but also creative which got her through.

Just a couple points, if I may.  The sextant I've used for the last 35-40 years has been a Simex Jr.  It has been an outstanding instrument.  At the lower end of quality sextants, it has a telescope, verier micrometer, four shades, and 120-degree limb, and has done everything I've ever needed.  I doubt the purchase of a Plath can be justified for use from the deck of a small boat IMHO, eventhough they are beautiful, unless you just need something to go with your caviar, champagne, and Rolls.
(2) For those who would like to master celestial, rather than just trying to learn enough to get by, I cannot recommend strongly enough taking the U.S. Power Squadrons courses.  They're comprehensive, and beyond minimal cost for materials, are free.  After taking those, I passed both elements of the Coast Guard celestial exams with perfect scores---a tribute to the courses, not me.
(3) To perfect the 'art' of celestial, the only way to do that is take several hundred sights from the beach so you can compare your LOP's with a fixed, known position.  This perfects your technique and shows what discrepancies are being created by what errors----not swinging the arc properly, not kissing the horizon or dipping the body, improper timing or recording techniques, using the sextant upright or inverted until you reach the last micrometer adjustment, sextant adjustment errors, getting equally reliable positions with sun, moon, planets or stars, etc.  Yes, I know people have taken off on a wing and a prayer, but I know a lot whose prayers weren't answered.  I know of one who set off from the West Coast in a 19-ft. boat.  He had a sextant and some books, and while he didn't even know pilotage, let alone navigation, he reasoned if he started sailing west and began reading, before he passed the Hawaiian Islands, he could figure out where he was and navigate the rest of the way.  While he was a great friend and I wouldn't disparage his accomplishment, I feel there's way too much luck needed there for the prudent navigator. 

Just out of curiosity... Where did he end up sailing to?

I certainly don't mean to tell anybody they shouldn't learn celestial.. I plan on learning it, and I plan on having a decent sextant aboard. By all means, learn as much as possible and, if you have the money, get a decent sextant. I just don't think you should stay home just because you don't have the $500 for one, or if you haven't 'mastered' it yet.

Tania was indeed lucky to make it to bermuda, but after that, she knew that her DR and her previous success in obtaining positions was enough to keep going. It was an informed decision. It wasn't until somewhere around the panama canal that she got her new sextant, making it that far was not luck. And I don't think she left NY relying soley on luck either, it just happened that way.

I would never recommend relying completely on luck in any situation, and I don't know anybody else who would...

I have a Davis Mk 15, and my personal best fix with it is 2 nm from a FIXED position on land.

With a plastic sextant, check the index error before each site.  That's what I do, though I've not noticed a LOT of problems with warping so far.

I'll second (or third, etc) the comment that to become proficient with it, you need to take HUNDREDS of sites from known locations.  It's a skill that demands practice.

But I find celestial extremely fun...the traditionalist in me, I guess.

Best of luck.       :)

thanks guys yes the Davis Mk 15 I have read lots of good things on this one and I will probally order it next week so I can start practicing.
Thanks for the input

Chris

Wow! Looks like the Davis Mk 15 is available on sale for under $130!

Too bad I'm spending boat points this season on an emergency gas generator for the house (after being without power for 2 1/2 days during the last ice storm).

It looks like a much nicer unit than my antique Heath--which I guess I'll keep at home as a relic of an earlier time.

Merry Christmas!

--Joe

Response to dnice's inquiry.  He left Southern California, and if I remember correctly, landed on O'ahu.  The original boat was sold in Hawaii. He acquired an English pilot cutter by John Alden, and later sailed back through the Panama Canal, all of the East Coast, Azores, Med, Madeira, Canaries, Cape Verdes, Caribbean.  I won't mention his name or his boat's name.  I made the mistake of doing that once, and he got really upset.  He doen't like publicity.  However, he's a really neat guy that I feel privileged to have known.  In fact, one of our granddaughters is named after his daughter. 

Just another note related to the discussion of sextants and celestial navigation.  This is an all too common scenario.  I had stopped in Bermuda for one leg of a delivery and learned of a boat that was missing.  After it was towed in, I talked with the skipper.  We all make mistakes, so I'm not denigrating him or his problems in any way, but we all need to learn from mistakes, ours or others, rather than emulating them.  One of the big mistakes is relying on electronics rather than fundamental skills.  He and his wife had dreamed of buying a boat, retiring, and following the sun.  Life got in the way, and he never seemed to find time to learn celestial.  But, what the heck, the boat had loran and satellite navigation, and he could always study celestial as he went.  They took off for Bermuda.  Of course everyone knows, depending on installation, it's rare that loran will get you all the way to Bermuda.  He followed the loran to Bermuda, and Bermuda wasn't there.  He then followed the satellite navigation to Bermuda, and BERMUDA WASN'T THERE EITHER!!!.  I don't know what the problem was there.  Anyhow, he set up a search grid looking for the islands, a dangerous idea considering some of the reefs extend out to or a bit beyond the limit of visibility for the low-lying islands.  Three days into this search grid his wife mutinied, and said, "You will put out a distress call."  The navy homed in on his signal, and dispatched a plane, finding him 150 miles NE of the islands.  A ship went out and took him in tow, but of course the navy isn't going to spend two days towing him back at 6 knots.  Bounding through the seas at well above hull speed, the bower anchor unshipped and hung over the side with each wave slamming the anchor into the topsides.  It was indeed a sad sight to see a brand-new Cabo Rico with the hull stove in---a terribly expensive lesson, far above the cost of learning celestial.

ouch...  having multiple, independent and redundant ways to confirm your position is a good thing.  Just curious as to how someone could be 150 miles off using satellite navigation, whether it was the older kind or GPS.

Quote from: thistlecap on December 24, 2008, 03:13:28 PM
Just another note related to the discussion of sextants and celestial navigation.  This is an all too common scenario.  I had stopped in Bermuda for one leg of a delivery and learned of a boat that was missing.  After it was towed in, I talked with the skipper.  We all make mistakes, so I'm not denigrating him or his problems in any way, but we all need to learn from mistakes, ours or others, rather than emulating them.  One of the big mistakes is relying on electronics rather than fundamental skills.  He and his wife had dreamed of buying a boat, retiring, and following the sun.  Life got in the way, and he never seemed to find time to learn celestial.  But, what the heck, the boat had loran and satellite navigation, and he could always study celestial as he went.  They took off for Bermuda.  Of course everyone knows, depending on installation, it's rare that loran will get you all the way to Bermuda.  He followed the loran to Bermuda, and Bermuda wasn't there.  He then followed the satellite navigation to Bermuda, and BERMUDA WASN'T THERE EITHER!!!.  I don't know what the problem was there.  Anyhow, he set up a search grid looking for the islands, a dangerous idea considering some of the reefs extend out to or a bit beyond the limit of visibility for the low-lying islands.  Three days into this search grid his wife mutinied, and said, "You will put out a distress call."  The navy homed in on his signal, and dispatched a plane, finding him 150 miles NE of the islands.  A ship went out and took him in tow, but of course the navy isn't going to spend two days towing him back at 6 knots.  Bounding through the seas at well above hull speed, the bower anchor unshipped and hung over the side with each wave slamming the anchor into the topsides.  It was indeed a sad sight to see a brand-new Cabo Rico with the hull stove in---a terribly expensive lesson, far above the cost of learning celestial.

good story I was telling a friend I was wanting to learn to use a sextant and he was like get a GPS and I was like what if it failed.. People these days just rely on electronic devices way way to much. I am guilty of this one to I have a cell phone. I have wonderd what happend if all cell phones died just for a day what on earth would people do.
I'm gonna order the mark15 sextant next week, I think it is very important to learn to use it, if I can only remember what website sold it for under 130 LOL

Chris,

  Might want to take a look at this thead too;

  Okay, so the GPS is broken... Anyone teach me the sextant? (http://sailfar.net/forum/index.php?topic=174.0)

Lots of good lesson material, and links you might find helpful.

(and go back and read this thread from the beginning.  I think the KISS sextant is a cool idea you might want to take a look at.

Quote from: chris2998 on December 24, 2008, 09:47:22 PM

Quote from: thistlecap on December 24, 2008, 03:13:28 PM
Just another note related to the discussion of sextants and celestial navigation.  This is an all too common scenario.  I had stopped in Bermuda for one leg of a delivery and learned of a boat that was missing.  After it was towed in, I talked with the skipper.  We all make mistakes, so I'm not denigrating him or his problems in any way, but we all need to learn from mistakes, ours or others, rather than emulating them.  One of the big mistakes is relying on electronics rather than fundamental skills.  He and his wife had dreamed of buying a boat, retiring, and following the sun.  Life got in the way, and he never seemed to find time to learn celestial.  But, what the heck, the boat had loran and satellite navigation, and he could always study celestial as he went.  They took off for Bermuda.  Of course everyone knows, depending on installation, it's rare that loran will get you all the way to Bermuda.  He followed the loran to Bermuda, and Bermuda wasn't there.  He then followed the satellite navigation to Bermuda, and BERMUDA WASN'T THERE EITHER!!!.  I don't know what the problem was there.  Anyhow, he set up a search grid looking for the islands, a dangerous idea considering some of the reefs extend out to or a bit beyond the limit of visibility for the low-lying islands.  Three days into this search grid his wife mutinied, and said, "You will put out a distress call."  The navy homed in on his signal, and dispatched a plane, finding him 150 miles NE of the islands.  A ship went out and took him in tow, but of course the navy isn't going to spend two days towing him back at 6 knots.  Bounding through the seas at well above hull speed, the bower anchor unshipped and hung over the side with each wave slamming the anchor into the topsides.  It was indeed a sad sight to see a brand-new Cabo Rico with the hull stove in---a terribly expensive lesson, far above the cost of learning celestial.

good story I was telling a friend I was wanting to learn to use a sextant and he was like get a GPS and I was like what if it failed.. People these days just rely on electronic devices way way to much. I am guilty of this one to I have a cell phone. I have wonderd what happend if all cell phones died just for a day what on earth would people do.
I'm gonna order the mark15 sextant next week, I think it is very important to learn to use it, if I can only remember what website sold it for under 130 LOL

When I was in New Orleans after katrina, the cell phone networks stopped working for about 6 days or so (all phones, landlines and cells, were simply overloaded and rendered useless)... It was a serious wakeup call for me. I was amazed at how helpless the majority of people were without phones and TV. I really can't explain what it was like, it was simply disgusting...

GPS is great, but IMO the biggest problem with it, is that it is controlled by the US government. At any time, without notice, the DOD can simply decide not to allow public usage of the GPS system anymore.... Although its becoming more and more unlikely, the more americans are using it, the more of a commodity it becomes, and the govt. are more likely to implement a system of their own, and leave the current system for public usage....hopefully.

I think the most likely scenario is a lightning strike... You could loose every electronic onboard, including handhelds and whatever you had for backup... This could happen 20 miles from shore as well as 1000. So having backups is important, but as Adrift just pointed out, independent and redundant is the way to go... You need more than 1 way to navigate, and each of those ways should be entirely different than the other.

I would like to say that celestial nav will be my primary means.. It would be best that way, but more than likely I will rely on GPS and use celestial as a backup.... hopefully I will be diligent enough to keep practiced up and use GPS just to confirm my positions... How hard could it be to take a sight twice a day??? what else are you going to be doing on a 30 day passage :)

Just remember—Celestial Navigation isn't really meant for use when in sight of land, since coastal pilotage is far more accurate. 

Most people don't realize that you don't have to be all that accurate when doing Celestial Navigation, since you're generally in open ocean when you're really using it...and being off by a mile  or four isn't all that important when it comes right down to it...when you're talking about hundreds or thousands of miles.  The more accurate you can be the better, but you don't NEED pinpoint accuracy to get to land most of the time.

If you can see land, having charts and an idea of where you are is important, but if you know where you are to the nearest five miles or so, the coastline will generally tell you exactly where you are—provided your coastal pilotage skills are up to the task.

Quote from: dnice on December 24, 2008, 10:54:20 PM
How hard could it be to take a sight twice a day??? what else are you going to be doing on a 30 day passage :)

Actually you should be taking at least three sights for a minimal noon position, two morning lines to advance and the noon sight.  The reason for a third line is that two lines will always cross somewhere, but you have no clue about the precision of your fix.  With three lines you either get a pinwheel (where all 3 lines intersect in the same place) or a triangle.  The pinwheel you can be confident in, while the bigger the triangle the less accurate the final fix.  It's a good check on the math as well as the actual sights.

Just for fun...

Yves is great, he cracks me up  ;D

Sextant video (http://www.youtube.com/watch?v=ZXiuKbH_8BU)

I like Yves in the cape horn video wearing the baggy purple bib shorts......just too darn cool  ;) I guess no one can see you out there...thank goodness. He is a fine sailor and inventer ...ya gotta give him that.

Awesome video clip. :) First time I have heard Yves speak. ;D Grog!

Funny how things happen...  Just after this thread, I was at a "social gathering" the other night where a few other sailors were in attendance.  We got talking sextants and one guy says he bought a Davis Mk3 sextant to take a class but hasn't used it since.  I ended up swapping him a case of beer for it, not that I need one but thought there might be interest here...  now listed in the SellFar section - no personal profit, just want to get my case of beer back.   ;D

Bill,

  Enjoy a grog for your trouble.  Thanks for thinking of everyone here (or at least whoever winds up with it).   ;D

FWIW, after this discussion (plus some PMs with Chris), I took my 1904 Heath of London sextant out of its case and looked at it carefully.

My conclusion: If I ever want to do celestial navigation on a boat, I'm going to need a newer instrument, probably a Davis Mark 15.

Back when I was a student (my 40th college reunion is this spring), I had little trouble reading an old-style vernier index. But that was on land and before I got glasses. This kind of sextant is probably fine for use on the deck of a large ship--in relatively calm weather. But my older eyes had a very tough time reading the index.

Shackleton probably used a similar sextant, in a lifeboat no less, but I have no illusions about comparing myself to such a great seaman and navigator.

--Joe

Picking up an old thread,
If I am able to get a good deal on an old sextant and intend to use it both for learning and for actual use on a small boat, should the vernier versions be avoided in favor of micrometer?

I bought a Frieberger sextant some years ago. Warnings for second hand, if you can't check them first. mine had an index error of "to much" , would cost a great deal to get fixed.

Thanks!
Perhaps the best choice is a Davis MarkIII with an artificial horizon until I am proficient enough to make an informed decision.

I just bought a Davis Mark 25 on ebay.  My first sextant :)  I have a 5 week celestial navigation class starting in a few weeks, can't wait ;)

Quote from: SeaHusky on January 16, 2012, 05:53:29 AM
Picking up an old thread,
If I am able to get a good deal on an old sextant and intend to use it both for learning and for actual use on a small boat, should the vernier versions be avoided in favor of micrometer?

The micrometer is generally preferred over the older vernier scale. When I was studying celestial navigation in college, more than 40 years ago, we practiced on vernier sextants--and I bought one of them from the university. It's a beautiful artifact, more than 100 years old, but I'd have a hard time trying to read that scale, especially on a pitching SailFair-type boat. (My eyes aren't what they were as a student, and we only practiced on land.)

I'd suggest looking for a Davis plastic sextant, if you want to go cheap. There's even a book, written by David Burch at StarPath (www.starpath.com (http://www.starpath.com)) that specifically discusses getting fairly accurate fixes with a plastic sextant. Here's a link to the relevant chapter of that publication:

http://www.starpath.com/online/celestial/plastic.pdf (http://www.starpath.com/online/celestial/plastic.pdf)

Please note: I bought a Davis plastic sextant at a very good price from our own Kurt (Cap'n. K), but I have yet to practice using it. My own coastal waters have very limited clear horizons, but it's on my long to-do list.

Good Luck,

--Joe

I also have a davis mk. 25 from ebay. It seems to be in pretty good condition though one of the mirror clips had snapped. I bought spare ones from davis instruments.

I'm not sure if I would prefer the mk. 15 with the half silvered mirror as opposed to the beam converger. I've only tried the mk.25 and there's not much opportunity to test drive others. The astras, freibergers, plaths and tamayas that appear on ebay are very tempting though.

I'm building a fair collection of books on the subject too. None have stood out as THE tome to have. My biggest hurdle is getting all the jargon into my head such that it I understand the concepts being explained. It's coming slowly, more through repetition than 'eureka' moments.

Quote from: gpdno on January 16, 2012, 10:34:03 AM

I just bought a Davis Mark 25 on ebay.  My first sextant :)  I have a 5 week celestial navigation class starting in a few weeks, can't wait ;)

Quote from: jpfx

I'm building a fair collection of books on the subject too. None have stood out as THE tome to have. My biggest hurdle is getting all the jargon into my head such that it I understand the concepts being explained. It's coming slowly, more through repetition than 'eureka' moments.

I haven't finished it yet, and I really did not ever intend it to be a replacement for a good book or an actual course on CN, but I did start this thread on celestial navigation (http://sailfar.net/forum/index.php/topic,3089.0.html) a while back.

Thanks! Oldrigs link was very enlightening as to the limitations or rather extra work necessary with the plastic sextant.
Is an artificial horizon worth having as a learning aid?

Quote from: SeaHusky on January 18, 2012, 03:02:15 AM

Is an artificial horizon worth having as a learning aid?

I think so.  I've used mine for practice quite a bit, especially when we lived inland...way inland.

It is my opinion that using a sextant is not something that can be mastered from reading it once in a book.  I think a lot of GPS-but-have-a-sextant-as-back-up sailors do this...buy a sextant and the site reduction tables, along with a book (or index card) describing the basic procedure and thing they are good.

I disagree.  I think it requires hands-on practice with the sextant to get good at taking sights.  Without good data from the measurement, all the calculators and tables in the world won't make a good fix.

And using the sextant well, while not hard per se, is harder than it seems from most 'book definitions.'

The more you practice, the better you will get.

My half-cent.

Quote from: Captain Smollett on January 18, 2012, 09:55:36 AM
And using the sextant well, while not hard per se, is harder than it seems from most 'book definitions.'

The more you practice, the better you will get.

John,

I couldn't agree with you more!
In the words of Hewitt Schlereth, author of Celestial Navigation in a Nutshell:

"Learning to use a sextant is a lot like learning to shoot a rifle. ... You can read about celestial navigation till the cows come home, but you won't learn it until you do it."

--Joe

Dunno if this helps...... but fwiw......   
http://www.landfallnavigation.com/kcnb.html

Today I got an offer to buy a Zeis sextant, new and never used. anyone any info on it? asking 900USD resonable???

Just to clarify, isn't it the east german "Zeiss Jena" manufacture?

found out. used by the russian marine...Recommended among sailing community. as far as I can see...

I feel I need to jump in here.....

I'm pretty old school, and even though I may have a number of GPS devices,  I'm always going to have my trusty sextant aboard. To keep in practice, I still use it to double check the electronics. 

If your not in a huge hurry, be patient, watch Ebay.. do up a saved search.  "Watch" the ones that are of interest to you, set yourself a fixed price of what you want to spend, and don't bid over your preset limit.  If you loose this one, another will come along.   I know 2 people in the last year, that have come away with real deals.  One with a nice Tamaya for $400, and a MAC for $305.   

For the most part, as long as it's a name brand device, the mirrors and optics are intact, the quadrant isn't bent, with the original certification in the box, your good to go. 

It's been my experience, most of us tend to like the style of sextant we originally learned on...

Even though Starpilot has a fantastic program for the TI-89 calculator ( and I do have one  ;) ) , I recommend always having the proper reference materials on board.. so when the GPS fails, and you can't find a couple of good AAA batteries in the Galley... you can still get a clue about which Ocean you're in.  ;D

Cheers
Bob

Good suggestion, Bob. That's why I carry a slide rule in my nav kit.  ;D ;) ;D

Found another not that expensive one... But the seller dosn't know what "brand" the text is in Russia... anyone knows? suggestion of bying? 
it's from 1983.

Quote from: ntica on January 22, 2012, 02:02:07 PM
Found another not that expensive one... But the seller dosn't know what "brand" the text is in Russia... anyone knows? suggestion of bying?  
it's from 1983.

Do you have a picture of the text? There are several of us (myself included) who can read Russian.

Is the seller in Russia? Or is the seller in India? If India, I'd be careful, because lots of sextants were left on board ships that were taken to India to be broken apart.

If Russia, also be careful, since that's the home base for lots of internet fraud.

A lot of Soviet optics were high-quality but very heavy. On the good side: Russian military items were built to take a lot of punishment because they were often not well maintained. On the bad side: A lot of Russian military items were subjected to a lot more punishment than they were designed for.

My recommendation: Don't spend too much on this item. Then, if you can't use it for navigation, you might be able to use it as an interesting artifact.

--Joe

Hi. here's a pic from the front of the box Oldrig...appriciate it!!!
And the seller is from Sweden.

Quote from: ntica on January 24, 2012, 02:42:01 PM
Hi. here's a pic from the front of the box Oldrig...appriciate it!!!
And the seller is from Sweden.

Ntica:

The sextant is a model "SNO-T" (a joke in English, but a model in Russian), which was a standard Russian sextant.

The other phrase "made in the USSR."

I can't find much information on this model, except that there are a number of them for sale, and that they were considered solid, reliable (but heavy) instruments. They apparently have an oversized mirror, which is definitely a positive.

Here's a commentary about the "SNO-T" sextant that I found on the internet. Of course, the source was trying to sell one of these--and he did sell it:

QuoteOVERVIEW: I have been particularly impressed with the Russian CHO-T sextants as a good alternative to the premium brands such as both Plaths and Tamaya. It also makes sense to invest in one rather than plastic which commands very high prices for what they are, and any sextant with smaller mirrors.

In our opinion, Russian sextants are becoming better known in this country, and there prices have been on the rise. This is because of their large mirrors, compact size, quality optics and overall good construction found only in the serious sextants. However because so many of them are sold with only scopes that show the image upside down they may nit always be a good buy. The design of the CHO-T has some features similar to the Freiberger, but is smaller, by almost one inch on the vertical measurement which makes it ideal on small yachts. Some of the parts, such as mirrors and the tangent screw, are interchangeable.

Those who have used this model sextant at sea, speak very highly of it. If you are a small boat navigator make sure to keep the enclosed tangent screw free of salt water and lubricated with WD-40 and you will have no problems. You also will welcome the light weight and full size mirrors of a CHO-T compared to other lesser cost alternatives.

Since the seller is in Sweden, I'm assuming that you will actually receive the sextant if you order it.

If the price is similar to a plastic sextant, I'd think it might be worth the gamble. After all, unless it's bent, you can repair a metal sextant.

The only caution I could think of would be in connection with the weight: getting good sights with a heavy, metal sextant on a small boat might be tricky. But, in any case, you'll have to practice shooting with the sextant until it becomes second nature.

Best of luck,

--Joe

Thanks a lot...yes I think I'll go for it, He asking 275 USD... fair price I think!
This was really helpfull Joe...
Just talk to "him" over the phone. The sextant was  bought by his father many years ago, of a USSR marine officer while at dock in Karlskrona harbour, (well know military marine harbour) never used, comes with some spares mirror.
Got it for 200USD ;D
again appriciate the help Joe!!!

Ntica:

If this sextant is indeed the equivalent of a Plath or a Tamaya -- or even a new Davis Mark 25 plastic sextant -- you're getting a very good piece of navigational equipment at an excellent price!

--Joe

Here's the rundown on the construction of the SNO-T sextant. This website is a gold mine of information about all kinds of sextants (including my antique Heath sextant). This guy, a retired dentist from New Zealand, has made a hobby out of collecting and restoring sextants of all types:

http://sextantbook.com/category/the-ussr-sno-t-sextant/ (http://sextantbook.com/category/the-ussr-sno-t-sextant/)

--Joe