Materials for learning celestial navigation in an emergency

[El Pinguino]

Originally Posted by RaymondR

Best advice so far on this thread.

Do you really think so when the OP was specifically asking for info about celestial.

I don't.

A nice neat sight book there Sea Scamp

[blackcrow]

There is NO "emergency" celestial navigation, you know how to do it or you do not know. you (practise) do that every day or at least any time you can otherwise you will forget how to do it if you are only waiting for few months or years to do it in an emergency. There is noting in between. ask this man.....



Yachtsman rescued twice after trying to sail 300 miles using APP | Daily Mail Online

[RaymondR]

I have a good quality sextant in it's storage box where it has been for the last twenty nine years. Way back then, in the mists of time, I used to religiously update my ephemeris tables and maintained a rated time piece. I would practice with the sextant and calculate lines of position regularly. I was very happy to see the end of all the expense and bother after I bought my first GPS.

If you are concerned with being dependent on electrical or electronic systems then you need to get paranoid about redundancy, which, from a practical viewpoint in the modern world means go out and buy a portable, battery operated, waterproof, GPS, some appropriate charts which you can have laminated and a couple of china pencils.

I believe that there are, or soon will be, three GPS nav systems and that chip producers are providing GPS engines which will access all three. With three systems and redundancy of on-ship equipment reliability should not be an issue.

If you are interested in traditional systems of navigation and want the intellectual exercise learn to navigate with a sextant and chronometer but it is far more practicable to go the redundancy route if you want to be able to accurate position fixes at sea.

[MBWhite]

Well it looks like the originator of this thread posted it back in February so with no follow up I'm assuming it is a somewhat irrelevant question, however I do feel compelled to state what my approach would be.

As mentioned, celestial is somewhat of a skill/art form that is at least to me not like riding a bike where you can forget all about it for a couple of years and then grab your sextant and figure out where you are at the drop of a hat.

A cover-all-bases approach for me would be to do what is previously suggested and get a backup GPS. Actually what I would do is pick up an old GPS enabled cell phone and put a nav app on it along with a bunch of charts where you will be sailing. You can pick up a waterproof Kyocera Hydro for under $15 used on ebay, and a while ago Boost Mobile was selling them new for $20. (got that tip from someone on the forum here). Get a 12V charger for it and if you really want to be Robinson Crusoe buy a solar cell phone charger too.

Anyway, you now have a GPS and maps for your area and so now you can start browsing all the tons of celestial nav PDF books that are available for free download and put them on the phone too. Make sure to put on the phone H.O. 249, available free and a couple star charts and star finder apps and you're set to where if you ever want to learn celestial you'll have everything you need to know including the reduction tables at your fingertips and you also have a full featured navigator as a backup if need be, and all for less than what one book would cost otherwise.

[Svanen]

Originally Posted by Jammer Six

I'm curious. How will a DVD help on a life raft after "...all electronics fail"? As a cute little signal mirror?

Instead of Buckley's video, the op could photocopy chapter nine of his 1970 book Airborne: which provides the same step-by-step instructions, in printed form (18 pages).

I agree with the comment that the presentation in Mary Blewitt's book isn't great. Instead, I recommend Tim Bartlett's RYA Astro Navigation Handbook, which has worked examples that illustrate how to reduce various sights. Dearn's printed forms, available here, might also be helpful.

[MBWhite]

For emergency use, I suppose it would be difficult to get more basic information than what is printed in the Davis Mark 3 Sextant operator manual:

http://www.davisnet.com/product_docu...0_IM_00011.PDF

[CVAT]

Reading these post, many have answered the OP's request, while yet others interject, get a GPS or other such drivel, no offense intended but please read and understand what the OP has requested.

[Adelie]

Originally Posted by CVAT

Reading these post, many have answered the OP's request, while yet others interject, get a GPS or other such drivel, no offense intended but please read and understand what the OP has requested.

You seem to be missing a few things about this forum .

1) The OP was not asking a single person face to face for advice. They asked a large completely anonymous group of people for advice. Consequently they got a lot of advice that they didn't ask for because of:
-the limitations of the written word,
-folks that didn't pay attention to all the info the OP gave or didn't see subsequent answers,
-folks seeing them as a newb who is biting off more than they can chew and wanting to help them look out for themselves, . . .

Posters will continue to get those responses no matter how much they disclaim to keep the discussion on topic. My suggestion is to say "Thank You" to the advice that pertains and to ignore the advice that doesn't and then keep reading. Some of it will be worth consideration even if it doesn't pertain to the immediate question. Having seen this situation enough times on the forum if you keep trying to control the topic you will wind up getting flamed and the consensus will become that you are an ass.

2) This is not a business situation where the goal is obviously constrained and time is money so people are inclined to stay focused. Also there is minimal hierarchy here so there is no good mechanism to keep the discussion on topic. Acting like it is a business meeting will just annoy people and lead to the aforementioned flaming and consensus.

3) While the folks that can afford a 100'+ boat are generally bright enough not to jump straight to that size alone, there are plenty of folks that can afford 50'-60' that would. They come on this forum periodically. Hence there is a lot of extraneous advice.

If you can accept the forum for what it is you can get at least some of the answers you are looking for. Fight it and you will drown.

[Jerry Woodward]

You don't even need to buy a sextant. Get the Android Sextant app and make your sightings with your smartphone or tablet using Google Sky and the phone's camera, let the app do all the calculations for you and then it will plot your position on a map.

https://www.youtube.com/watch?v=qsErtrttJsY

Of course, then you can check your fix with the phone's GPS.....

[Swammy]

Originally Posted by Sam Plan B

William F. Buckley produced a DVD many years ago in which he went through the step by step process for reducing a sun sight. The DVD is still available on line. I have one myself. It is titled, "Celestial Navigation Simplified. Go to bennettemarine.com. Highly recommended.

Here is the youtube link to this free video.

https://www.youtube.com/watch?v=b5dIJsMCd2I

[jackdale]

Tom Cunliffe - Celestial Navigation

Short and sweet.

[tominny]

I am the OP.

Thank you very much for all the useful comments. I should say that I asked the question less for use in an emergency but more for learning celestial navigation as a useful means for passing time on a passage. I have several GPS receivers on board in various shapes and forms including a battery-operated one in a Pelican case. The chance that they all fail is small but not impossible. The chance that the US government shuts down the GPS system is even smaller (unless you are into conspiracy theories) and even then the iphone 4S and later also support the Russian glonass system.

At some point I'd like to upgrade my Yachtmaster Offshore license to Oceans, which requires a documented voyage by celestial navigation. So that and the curiosity about a nautical tradition that is disappearing are the main reasons to learn this.
It seems though it's more of following a particular sequence of actions and easy calculations than really understanding what's behind it all. There seems to be many ways to skin this cat. Maybe just get an old salt to show me his way of doing it and copying his sight reduction sheets is the least painful way to go?

[El Pinguino]

Originally Posted by tominny

I am the OP.

Thank you very much for all the useful comments. I should say that I asked the question less for use in an emergency but more for learning celestial navigation as a useful means for passing time on a passage. I have several GPS receivers on board in various shapes and forms including a battery-operated one in a Pelican case. The chance that they all fail is small but not impossible. The chance that the US government shuts down the GPS system is even smaller (unless you are into conspiracy theories) and even then the iphone 4S and later also support the Russian glonass system.

At some point I'd like to upgrade my Yachtmaster Offshore license to Oceans, which requires a documented voyage by celestial navigation. So that and the curiosity about a nautical tradition that is disappearing are the main reasons to learn this.
It seems though it's more of following a particular sequence of actions and easy calculations than really understanding what's behind it all. There seems to be many ways to skin this cat. Maybe just get an old salt to show me his way of doing it and copying his sight reduction sheets is the least painful way to go?

Try this https://www.dropbox.com/s/oxduof5rsz...ation.pdf?dl=0

Let me know if its a dud link....
Ping

[Adelie]

Originally Posted by tominny

I am the OP.

Thank you very much for all the useful comments. I should say that I asked the question less for use in an emergency but more for learning celestial navigation as a useful means for passing time on a passage. I have several GPS receivers on board in various shapes and forms including a battery-operated one in a Pelican case. The chance that they all fail is small but not impossible. The chance that the US government shuts down the GPS system is even smaller (unless you are into conspiracy theories) and even then the iphone 4S and later also support the Russian glonass system.

At some point I'd like to upgrade my Yachtmaster Offshore license to Oceans, which requires a documented voyage by celestial navigation. So that and the curiosity about a nautical tradition that is disappearing are the main reasons to learn this.
It seems though it's more of following a particular sequence of actions and easy calculations than really understanding what's behind it all. There seems to be many ways to skin this cat. Maybe just get an old salt to show me his way of doing it and copying his sight reduction sheets is the least painful way to go?

Yeah there is a lot of technical stuff that gets in the way of understanding the underlying ideas. The guy that taught me originally never really covered what it was that I was measuring and how it pertained to where I was. I could do the work but understanding it was different. Here's what I ultimately figured out on my own:

When you measure the angular distance between the horizon and a celestial body you are also essentially measuring the range to that body. Knowing the range to something you can draw a circle of position around it an know that you are somewhere on that circle, this is just like navigating with landmarks that you can see or that show up on a Radar plot.

There are complications to that; starting with the fact that the body is moving, but since the movement is predictable you can still draw a circle of position around the body at the instant you took a sight. The trick here is have very accurate time.

The next big complication is that any globe you could plot your COP on would be too big to conveniently carry on a boat and any flat map of appropriate scale would distort the circle beyond usable accuracy. The trick here is calculating what height and direction to the body would be from where you think you are and comparing that to the actual measurement to get some numbers you can actually draw on a map. All the different methods are about the particular way the calculated height and direction is arrived at. Some methods are easier and less error prone but take more time and are larger and heavier to carry. I'm in the process of going thru the major methods and comparing. If you are still interested, bug me in a week or so and I'll post the results here.

[El Pinguino]

For some reason the dropbox link I posted above doesn't want to work but the one inside here does... http://www.cruisersforum.com/forums/...ff-144799.html