Celestial Navigation: Have you ever relied on it?

[PatCassidy]

Either to determine your position or verify the accuracy of your position determined using some other means.

Or perhaps were you able to say "Hey, I was within a mile and a half of my actual position!"

Or did your sextant go aboard in its box and then disembark without coming out on deck.

Or did you take a sight, mark the time and then lose the piece of paper in your pocket?

I am guilty of the latter on more than one occasion.

[Tylerdurden]

I am still looking for a decent sextant. I cannot think of going out without one as GPS though reliable may go down one day either intentionally or by solar storm. The plastic ones are ok but not for serious nav.

[paladin]

within a mile and a half?
A pencil mark is two miles wide on a standard georef chart.......
I've known more than one dude circumnavigating with a davis plastic sextant...

[Tylerdurden]

within a mile and a half?
A pencil mark is two miles wide on a standard georef chart.......
I've known more than one dude circumnavigating with a davis plastic sextant...

I think I will stop worrying then. I got a lecture on not having a good one.

I am still trying to find the book someone wrote about the use of a Celtic Cross for navigation. It was here on the forum I think but I cannot find it. That sounds like a fun experiment.

[davidagage]

Celestial Nav is on my to do list as well as my christmas list.

Honneeeyyy, pretty pleeeze......;);)

[Kasey]

When Mom was in her 20's, she took a class in celestial navigation and then took off on a tiny little boat - like a 26 footer or something - and she and her then-husband went from California to Tahiti!

How accurate is she? Well, we never retraced our steps to find little bitty islands in the middle of nowhere, I know that for sure! Her sextant was beautiful - an antique, even in 1970, but it worked for her. I never stopped watching her plot the charts and draw lines and stuff.

Although I know absolutely nothing about it, I was fascinated with the concept that although the stars "moved" around in the sky, and we were constantly changing our position so the view of the stars was constantly changing as well, she never once got us lost.

I'm just as fascinated now as I was at 7 years old - and although it might not have hurt us to have some of the fancy new stuff, Tylerdurden makes a valid point when he says electronic devices go down. I'd like to take the class - or at least read a book - just to see how that stuff works - how mom was able to do what she did, with no official certification or anything, just a short class.

[JollyTar]

I'm actually preparing to write my AstroNav examination next week. That said, I've used elements of astro nav many times. In northern lattitudes i check my compass against a pole sight on mornings when polaris and the horrizon are visible. I calculate great circle sailings for passage plans (though in practice we sail the plan based on the GPS). While not using it for nav, I've gauged my progress from panama to alasaka (and back and back ...) by the altitude of the pole star and the southern cross. I've never fixed my position using a marc St Helaire though I hope to the next clear twilight... Now that I know how that is... When it comes to sextants, I've been foretunate beyond all reason. My father (olde tyme master mariner) maintains a small maritime "museum" including a number of sextants ranging from the beginning of the 18th century to the 1960's (when he became an officer and got his "modern" sextant). He was planning on giving me his Weems and Plath upon my completion of my COC as WKM... Our friend Bob Lily (retired 85 yo mariner) beat him to the punch however and bequeathed me his simtex this spring. A magnificent instrument. I hope you follow your notions and learn your sailings and sights. Wish me luck on my exam.

Jim

[J. Dillon]

I got three sextants. One made by Brandis an old vernier pre WW2 model. Another small Japanese make with a micrometer drum. and a Davis plastic one. I used the old one to and from Bermuda see http://www.woodenboat.com/forum/showthread.php?t=61697 ( shows work sheets and plots)

I also used it several times during various cruises including in the South Pacific. I consider celestial navigation the prime method of position determination off shore and GPS the back up. I have gotten soft and use a calculator to reduce the sights now.;)

JD

[botebum]

When Dad worked for C. Plath we had literally dozens of high dollar sextants lying around the house, including several company owned antique models. I asked Dad what their composite value was at one point. He replied that he never bothered to tally them but that several waterfront homes with a boat for each could be paid for. I fiddled with a plastic model some but wasn't interested enough at the time to stick with it. Dad was a whizz at it because of the job requirement of demonstations at shows and such. When he went to work for Lockheed on the Shuttle Program, he kept a very nice presentation model on the credenza behind his desk. I always thought the contrast there was pretty cool. Shortly before his death, he sold the few that he had acquired through the job and on his own, not thinking that I might be interested in taking it up at some point. Oh well.

Doug

[TimH]

I heard its unreliable. Stars move around and sometimes fail to light up. Better off putting your money and time into something you can always count on...like GPS

[botebum]

I heard its unreliable. Stars move around and sometimes fail to light up. Better off putting your money and time into something you can always count on...like GPS
Someone's liable to take that seriously around here.

Doug

[JollyTar]

It's true, the stars move. However, there are just over twenty stars that are regularily used for navigation and the corrections for their movements are available in your nautical almanac. There is also an availability issue. You need the horrizon and the celestial body. If you can't see them, you can't measure the altitude. Not so many sights taken on the grand banks... yet another concern is refraction. Again, it's addressed in the almanac, however it's based on normal atmospheric conditions. If the altitude of your body is over 30 degrees then it isn't a problem. If you're trying to do lower merpass of the sun (eg. north of 60N) then refraction is likely to enter very signifcant errors into your calculations. The good news is, you can take a number of sights, even for the merpass. If you update your DR Pos'n with each calc, you'll be able to whittle it down to a reasonable "cocked hat". gps is definitely easy and readily available. However, there is a risk in rely solely on it. Without DGPS it isn't accurate enough for coming into many ports. (we always go into tuktoayuktuk on the compass if we can't see the ranges). It also is subject to damage or failure (the hardware) and can be made unavailable by decision of the US Airforce or Gov't and certain atmospheric conditions including solar storms. Ships making deep sea passages are required to carry a sextant, time piece and almanac. And the officers of such vessels are examined on astro nav. I wouldn't discourage anybody who was interested in developing this knowledge or skill from doing so. Of course, I have a GPS on my sailboat and I use it.

Regards,

Jim

[JollyTar]

hmmm it appears I was that someone.... did I miss some sarcasm? My mistake.

[TimH]

Lol :)

[TimH]

Sorry




dry sense of humor...

[JollyTar]

No problem... I'm the goof that responded to a joke....

[Andrew Craig-Bennett]

Using celestial navigation is like cooking - it is hard to learn, it requires regular practice, and it gives you something to do on a long passage.

I have not quite adapted to electronic systems.

[Kasey]

I think this is getting funnier by the minute! I read your post, TimH, and started laughing - but then I told my son about it (he's 13 and knows the kind of stuff my mom can do), and asked him if I should assume it was sarcasm...

He said to ask you, and I was like, "But what if he's SERIOUS??? He might get mad!" He mumbled something about GPS systems having about a 30% accuracy rate and bolted out the door to go eat dinner at mom's. :) I was like, the guy LIVES where there's a bunch of old salts - surely he was joking ... what will I DO???

I came back to check the thread and ... whaddya know! I didn't HAVE to ask!

Thank you so much for the brief education, JollyTar! :D It was actually way over my head, but gave me a tiny clue as to how the "magic" works.

[ishmael]

I have to chime in here, and I guess give a plug. Brother Bill, after much thinking by a not unintelligent mind, wrote a book on it. He claimed it was the most direct method, though he was a bit out of his mind. LOL

He coined a phrase, which might or not be true. "Celestial in Plain English" Never tried to use it. It's a bit overly didactic, but I suppose the subject would be.

I'm sure it's out of print, but if I ever try to learn I'll give it a try.

[botebum]

I really love dry, sarcastic humor, but only when I get it:D Maybe it's my northern European ancestry.

Doug

[Kasey]

... that sounds like the commentators referring to the New York Times cover - sarcasm is only good when it works!

I like dry humor myself - but I'm so scared of offending people who might take it wrong, I can't pull off the poker face thing like, say, George Carlin - I have to put in the grin. *insert grin here*

btw, is this whole tangent considered a thread hijack?

[paladin]

I started with an Arthur Piver book, "Navigation by Simulous" (so simple it's ridiculous) and the more he explained it the harder it got. Piver could not navigate, that's why he always referred to his "crew" and himself as the "skipper", he needed someone to not get him lost.
It was a basic noon sight, so that's how I started....then I discovered that you can use the same technique with the moon, then apply it to stars that I could identify....but I think it was about 1969-1970 that I was looking for a new sextant as I had an old U.S. navy job that weighed a ton that belonged to an uncle. Svend T Simonsen had just started the "Coast Navigation School" for learning Celestial, so I signed up for it, then eventually went to a weeks classes in Santa Barbara. I think I may have the old course material somewhere. Their top of the line sextant was made by Tamaya, a copy of the Weems and Plath, with polarizing filters instead of shade glasses. I still have it. Back then it was $450 for the "spica" model in a beautiful mahogany case. I think I saw a used one on e-bay for over a thousand bucks. I don't own a GPS 'cause the batteries dunno run down on the sextant....but I do have a couple of Tamaya navigational computers, but sometimes don't use them, they are a convenience.

[Claudia]

Celestial Nav is on my to do list as well as my christmas list.

Honneeeyyy, pretty pleeeze......;);)

Got it honey.:p

[paladin]

There's a place down the shore where I would go to practice.....but you can do it in your yard with a pie plate, some water and a teaspoon of veggie oil in the pie plate. Use the water surface as the horizon then divide the observed angle by 2.....

[Bill Lowe]

Ya its intresting to go on deck at twilight and the sky is like your backyard a frendly place you take your sights and go below to reduce. You know where you are sight by sight and your DR its home at sea.

[Hwyl]

Celestial Navigation: Have you ever relied on it?
Yes

[mtsailor]

Arrrgh mate. Back in the days before GPS (1979) I sailed a wooden sloop from The Canary islands to Barbados. Found Barbados on the first try, right where it should be, after 30 days crossing. My nav tools were a pretty good mechanical analog wrist watch, short wave radio to receive BBC time ticks, some pencils, and a $39.00 Davis Master PLASTIC sextant. The watch quit a long time ago, the radio bit the dust from a bad case of corrosion and the pencil erasers got all hard and the lead dull. The plastic sextant, now over 30 years old, still works like it did when new. With my fumble fingers & banging around in 20 foot seas, a brass sextant probably would have gotten so misaligned that I'd still be out there somewhere. Brass sextants are pretty in their wooden boxes on the coffee table and are at home on the cushy bridge of a large ship. For me, plastic ones work real good on small boats and they're cheap(er) -- take two along. Truth is that next time I'll play with the sextant and have a chart plotter and a handheld GPS as back-up.http://www.woodenboat.com/forum//images/smilies/smile.gif:). "Junior Member"

[WX]

I plan to learn.

[Dr.Spoke]

I learnt from my grandfather - Master Mariner . From 12 until I was 14 taking a sight alongside him, on a beach or at sea, was just one of the things we did. He had been honing my non-euclid geometry skills since i was about 9 - so I understood what I was doing.
I can still do the calcs, and use tables, and pull down a sight. The idea of only relying on a sight though. Even when I had no other navigation tools, observation of the sea, weather, currents, and dead-reckoning were/are always used to guage the accuracy of a sight - and/or GPS

[Larks]

After getting lost in all sorts of books on the subject I finally found "Celestial Navigation for Yachtsmen" by Mary Blewitt, very practical and straight forward and in my case it least I got to the point of being "confident" but not practiced. I need much more practice but now know enough to use the sextant confidently if I have to rely on it.

[PatCassidy]

I have found every celestial navagation book I ever looked at to be lacking. Either too complicated or too simple. And they all seem to be written ass-backwards. Sunrise and sunset at the back. I would put sunrise/sunset at the front of the book in chapter one which would be about arcs and time.

[Captain Blight]

I keep wanting to give it a try but there isn't a lot of call for it on the Mississippi and Ohio Rivers.

[Tylerdurden]

I think one has to do it live with an instructor. I was lucky that our navigator took it upon himself to teach anyone willing to learn.
Of course it was over 25 year since I used it so much refresh and practice is in order.

[paladin]

One of the things that I wanted but could never find an economical solution for was a direction finder......Then about 30 years ago I had a requirement for a cheap tracking device for a client.....I designed an adaptor box to attach to a convention radio receiver that is accurate to plus or minus 1 foot at 5000 feet. For a while I sold about 300 kits a month at 75 bucks a kit.....

[Tylerdurden]

One of the things that I wanted but could never find an economical solution for was a direction finder......Then about 30 years ago I had a requirement for a cheap tracking device for a client.....I designed an adaptor box to attach to a convention radio receiver that is accurate to plus or minus 1 foot at 5000 feet. For a while I sold about 300 kits a month at 75 bucks a kit.....

Is it like an adf? I would have bought one of those kits for sure.

[Captain Blight]

Seriously, Chuck, I would love to know what's involved in that....

HINT HINT HINT

[SaltyD from BC]

I studied Surveying in College (tech school) and worked as a surveyor in my 20s. I vaguely remember the tables for "star shots" which was the MO for bringing down precise control points in the middle of no where. Must have known enough to pass a test on it all too back then I gues.. Now of course that's all done by GPS and current land surveyors less than say 40 yrs old prolly don't know how to do it the old fashioned way at all.

Unfortunately through my surveying years I never got to practice it. As there's nearly always a control point not too far away. A lot corner, IP or monument. Unless your awaaaaay out in the boonies.

In 1980 I worked for BC Railway when they were building a new line through the Rocky mountains to Tumbler Ridge where two coal mines were being developed. This was definitely way out in the boonies. I was supposed to go out one night and do some star shots to bring down control but I ended up on another crew or something. I remember the guys that got to go telling me it was some cool. They dusted off a pile of old books, sobered up our old and crusty party chief who was the only surveyor in captivity that savied it all, and went out in the middle of the night taking shots of lots of different stars and formations from hour to hour with a one second theodolite. There was a hell of a lot of calculations to do the next day I remember. Still pissed that I missed out on that..

[PatCassidy]

I have an old text put together by Houston Marine. It wasn't bad. Though at times they still wanted to impress you rather than instruct.

What one needs to know about using the nautical almanac is in the back of the same. You can easily teach yourself sunrise, sunset and noon position.

[Ian McColgin]

Dad taught me from the Air Almanac when I was about 12 or 13 so it's really not so hard. I was using an old wind-up averaging sextant from Pan Am. My current sextant is the better Davis plastic.

One helpful thought - little boats bounce and move a lot and it's incredibly easy to loose your star as you bring it down. So turn the sextant upside down and bring the horizon up to the star. If you spent your youth correctly learning to shoot with both eyes open or drawing what you see in the microscope or something such, you can easily have one eye in the scope and the other providing more general context and thus more confident star identification.

G'luck