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22-02-2013, 14:16
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#1
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Registered User
Join Date: Feb 2013
Location: Long Beach, IN
Posts: 20
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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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22-02-2013, 16:09
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#3
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,420
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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).
b.
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22-02-2013, 16:27
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#4
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Registered User
Join Date: Dec 2012
Location: New Orleans
Boat: Bruce Roberts 44 Ofshore
Posts: 2,842
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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.
__________________
GrowleyMonster
1979 Bruce Roberts Offshore 44, BRUTE FORCE
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22-02-2013, 16:43
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#5
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Registered User
Join Date: Feb 2013
Location: Long Beach, IN
Posts: 20
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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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22-02-2013, 17:02
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#6
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,420
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Re: Self Taught Celestial
Quote:
Originally Posted by PCFithian
- assuming all electronics are unavailable,
- 5 or 10 miles,
- ~$700 on something that if all goes well, will never be used.
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- 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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22-02-2013, 17:56
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#7
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Registered User
Join Date: Dec 2006
Location: Cruising
Boat: Privilege 39 Catamaran, Exit Only
Posts: 2,723
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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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22-02-2013, 18:00
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#8
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Marine Service Provider
Join Date: Dec 2010
Location: Little Compton, RI
Boat: Cape George 31
Posts: 2,976
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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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22-02-2013, 18:15
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#9
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Registered User
Join Date: Nov 2011
Location: Montegut LA.
Boat: Now we need to get her to Louisiana !! she's ours
Posts: 3,421
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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 !!
__________________
Bob and Connie
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23-02-2013, 07:51
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#10
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Registered User
Join Date: Feb 2013
Location: Long Beach, IN
Posts: 20
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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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23-02-2013, 08:22
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#11
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Registered User
Join Date: Mar 2006
Location: Tampa Bay area, USA
Boat: Beneteau First 42
Posts: 3,961
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Re: Self Taught Celestial
Quote:
Originally Posted by PCFithian
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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.
__________________
"It is not so much for its beauty that the Sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
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23-02-2013, 08:34
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#12
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Registered User
Join Date: Jul 2012
Location: Texas - USA
Boat: Twin Otter de Havilland Floatplane
Posts: 1,838
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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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23-02-2013, 08:37
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#13
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Nearly an old salt
Join Date: Jun 2009
Location: Lefkas Marina ,Greece
Boat: Bavaria 36
Posts: 22,801
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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.
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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
__________________
Interested in smart boat technology, networking and all things tech
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23-02-2013, 15:22
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#14
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Registered User
Join Date: Feb 2013
Location: Long Beach, IN
Posts: 20
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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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23-02-2013, 18:04
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#15
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Marine Service Provider
Join Date: Dec 2010
Location: Little Compton, RI
Boat: Cape George 31
Posts: 2,976
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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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