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Old 22-02-2013, 15:16   #1
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Self Taught Celestial

After lurking around this forum for a while and learning a lot, I decided to join.

I am now in the process of teaching myself celestial navigation. So far, I've acquired a Davis Mark 15 sextant, "How to Use Plastic Sextants" by David Burch, "Long Term Almanac" by Geoffry Kolbe, and some plotting tools.

I've been able to gain a huge amount of information from these three sites:

http://celestial-navigation-course.com/start_course.php

Celestial Navigation

A Short Guide to Celestial Navigation

Another great item of learning I've acquired in a very compact form is the Davis Quick Reference Celestial Navigation, Celestial Navigation by Davis

If anyone can suggest a user forum for celestial navigation, please advise.

As I am just now embarking on this voyage, helpful tips are welcome and appreciated!
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Old 22-02-2013, 16:38   #2
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Re: Self Taught Celestial

NavList: for the Preservation and Practice of Celestial Navigation by Sextant

Not exactly a user forum, but a forum devoted to the history of traditional and celestial navigation. If you are interested in the fine detail of celestial, this is for you. Some very strong and robust contributors, many extremely well qualified. Some good resources.
Lee
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Old 22-02-2013, 17:09   #3
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Re: Self Taught Celestial

Astro is very easy. Just start with the basics, then move on to the more complicated matters.

I think it is in the Pacific Crossing Guide where the authors give a 2 page class that covers the hard core.

George Bennett's book is pretty good too and very concise.

I think the hard part is getting a clean and reliable sight from the deck of a small rolling ship (if you have the bad luck of having a small ship, that is).

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Old 22-02-2013, 17:27   #4
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Re: Self Taught Celestial

Www.celestaire.com is a good site for books and tools.

I know this is ginna stir up a controversy but I feel that a plastic sextant might be an acceptable backup, but a bad instrument to learn with. The reason is that the expected inaccuracy of a plastic sextant can mask small errors. A more accurate instrument reveals them. You need to be able to spot your errors both big and small so you learn not to make them. I would recommend an Astra IIIb which is still pretty cheap comparrd to a Plath or Tamaya or Freiberger, but nearly as accurate as these more expensive sextants.

I will offer my opinion on sight reduction methods. If you want to develop yiur celestial navigation skills primarily as a backup to modern methoda, I suggest you purchase and use paper almanacs and sight reduction tables, and absolutely not be reliant to the slightest degree on anything that uses electricity. Ideally your primary navigation methods use a GPS, whether you use paper charts or not, and maybe you have a batteryoowered handheld unit and paper chart or plot sheet for the rare event of a lightning strike or an inability to charge your battery bank. Then as the ultimate backup, sextant, tables, pencil, triangles and paper chart or plot sheet. No calculator or computer needed. Nor batteries.

If you just want to do celestial because it is fun or cool, then use the method that is the most fun or cool. But i would urge you to include the old school methods in your repertoire just in case.

If celestial will be your primary navigation method, then you will appreciate the speed and covenience of computer derived solutions. There are other advantages, such as being able to use your exact DR position as your Assumed Position instead of the nearest whole minute LHA. But once again you should be familiar with non electric non electronic sightcreduction methods.

One last thing... get serious about keeping an accurate DR. Your DR is very important. Sometimes it is EVERYTHING. You need to have confidence in your DR when you go a few days without an opportunity for an observation. A careful DR is the main differece between a good Navigator and a mediocre one.

Good luck and welcome to the dark side.
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Old 22-02-2013, 17:43   #5
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Re: Self Taught Celestial

My intent in learning celestial is to gain knowledge of this art and as a backup for future potential offshore navigation, assuming all electronics are unavailable. Hence my desire to learn using the Kolbe almanac, which includes sight reduction and is good until 2050. A compact, one book solution.

If I can learn this and do plots that are good to 5 or 10 miles, I will have accomplished my goal.

Many have learned with a Davis plastic sextant, and since it is for a backup only, I'm not keen in spending ~$700 on something that if all goes well, will never be used.
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Old 22-02-2013, 18:02   #6
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Re: Self Taught Celestial

Quote:
Originally Posted by PCFithian View Post

- assuming all electronics are unavailable,

- 5 or 10 miles,

- ~$700 on something that if all goes well, will never be used.
- assuming you have a very expensive mechanic timepiece?

- I think 5 only on a calm day, unless you are sailing a cat or a bigger mono,

- if it never gets used, then how do you want to learn?

;-)

I use a plain alloy sextant with great optics gotten s/h for about half the price. (Heavier than plastic and can be used as a weapon if boarded by tax officers or bigfoots).

b.
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Old 22-02-2013, 18:56   #7
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Re: Self Taught Celestial

I got an aeronautical bubble sextant from Celestaire, and I used it to take sights and navigate on land in the Arabian desert. If you take sights with a bubble sextant using the bubble as the artificial horizon, you can practice your celestial navigation anywhere.
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Old 22-02-2013, 19:00   #8
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Re: Self Taught Celestial

I learned heaps with a plastic Davis sextant, and then more with a lesser quality Ebbco before laying hands on an Astra IIIB. By all means learn on the Davis; getting all the tweaky numbers figured out is the biggest hurdle in learning. Once you're got the maths down, the big difficulty is getting good shots, but that's a matter of practice. If you want to know not only how things are done, but why they work, Bowditch has more information than I could digest in a lifetime, as well as a plethora of neat sextant tricks useful for piloting.
Though an expensive time piece would be nice, a $30 Timex has always worked for me. You can rate it to see how much it gains or loses, and how fast, before putting to sea, and checking it every few days against a radio time tick or GPS time or whatever is easy to do.
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Old 22-02-2013, 19:15   #9
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Re: Self Taught Celestial

Ive used the avaition tables and an a old Accutron watch for years ! it will and do get me where I wish to go !! take a site everyday I can ! and also star and planet sites when availble! lots of fun and good practice ! also I have my position only GPS, and Connie has her puter with the Capt system, between hers and mine we get everywhere and anywhere theres enough water !!
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Old 23-02-2013, 08:51   #10
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Re: Self Taught Celestial

Well, I do plan on getting a good timepiece that is coordinated with UTC and keep it in the sextant case. Maybe one of these? Or do you folks have an alternate suggestion?

WT-2165U by La Crosse Technology - Tomorrow's Weather Today
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Old 23-02-2013, 09:22   #11
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Re: Self Taught Celestial

Quote:
Originally Posted by PCFithian View Post
Well, I do plan on getting a good timepiece that is coordinated with UTC and keep it in the sextant case. Maybe one of these? Or do you folks have an alternate suggestion?

WT-2165U by La Crosse Technology - Tomorrow's Weather Today
You need a master time piece that displays seconds and a stopwatch that you can start at the moment you take your sight. You stop the stopwatch when your master time piece hits a whole minute and deduct the time on the stopwatch from that to get to the time of your sight. Absent having seconds on your master time piece, it is very difficult to stop the stopwatch at the precise moment the master clicks over a whole minute.
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Old 23-02-2013, 09:34   #12
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Re: Self Taught Celestial

Teknav's celestial navigation made easy... Look up Garmin.com ! Buy a portable/pocket GPS. Turn ON the GPS and wait a few seconds for a bunch of satellites to show up on your screen...and presto...you've got your Longitude and your Latitude; in degrees, minutes and seconds, of course...ummm +/- 25 ft, accuracy for el-cheapo pocket GPS. <Save your money by not buying a sextant! But if you are still determined to buy a sextant, you also need to buy an abacus and a slide rule to complete the set.> Mauritz
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Old 23-02-2013, 09:37   #13
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Quote:
Originally Posted by svHyLyte

You need a master time piece that displays seconds and a stopwatch that you can start at the moment you take your sight. You stop the stopwatch when your master time piece hits a whole minute and deduct the time on the stopwatch from that to get to the time of your sight. Absent having seconds on your master time piece, it is very difficult to stop the stopwatch at the precise moment the master clicks over a whole minute.
I had a stopwatch with a remote button. It broke unfortunately.

I was sitting in the office looking at my Astra. Thinking , a nice hi res greyscale encoded strip on the quadrant , encoder to the arm, digital clock with button. Bring down the sun , press the button , hey presto , degrees and time captured. ( even a little translucent OLED display in the sight line , giving real time readouts.........

( then I burnt myself at the nearest stake)

I couldnt disagree more with Growley, practice on a plastic sextant its fine. The main errors are temperature related on plastics. On a small boat your doing well to get 10 miles, 5 if you an expert. And yes do it all with pen and paper. Don't use any calculators until you've mastered it all. The vast majority of errors are made in the additions and the table extraction

Dave
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Old 23-02-2013, 16:22   #14
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Re: Self Taught Celestial

The time issue is solved for now with an excellent iPhone app called Emerald Timestamp. It can be set to UTC and is synchronized with with NTP and international standard atomic clocks, so it should be spot on. Right now on my iPhone, it is showing +/- 0.09 seconds. It does not use the iPhones internal clock.

It also has a large button that when pressed, records the exact moment and can be labeled afterward.

I'll use this for my training. The iPhone's compass app also gives me the lat/lon coordinates for verifying my plots.
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Old 23-02-2013, 19:04   #15
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Re: Self Taught Celestial

Another trick if you don't have a stopwatch is to practice counting ten seconds. Surprisingly easy after some repetition. Then you start counting (under your breath if someone is trying to sleep) from when the object was on the horizon. Ten seconds is enough to put the sextant down and look at the time on your Timex, from which you subtract ten seconds for the time spent counting. If you practice enough, you'll get to where five miles of error bums you out--when I was practising almost daily, I could get about half my shots within a mile. (whenever I bothered to check on the GPS, which I stopped doing once I became reasonably confident in my shots).
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