Celestial Navigation...Tough to learn?

[Didereaux]

Franklin, some day ...

Franklin, One of these Spring days(nights) give me a buzz, I'm just down the channel from you a bit LP. Finding those stars easily on a boat has some minor little tricks<grin> We'll split a beer and I'll gladly give you a hand.Hell, anybody who has made the effort to try is sharper by necessity than the coddled oafs I was referring to. hehg'Luk

 

[Ted]

Loran. Tell Me About It.

Please offer an explanation about Loran. Celestial, and GPS and Loran are all methods to navigate. Is Loran considered to be a dated method compared to GPS. I will one day outfit my boat (when I buy one) with serious navigation equipment and am looking for advice. I figure, it you don't really have a clue of where you are (exact location) and where your are headed (exact direction) you are lost and looking for trouble.Thanks

 

[Ross]

loran is

low frequency ranging and navigation. The method used is quite similar to GPS inso far as it measures the timing from widely separated radio transmitters each sending and signal. The limitations are the range of accuracy as you move farther from these land based transmitters. I have a Loran system on Bietzpadlin and in the Chesapeake Bay it is very good most of the time. I have found temporary errors in the signals on occasion that were serious enough to get me in trouble had I been relying on that alone. When the system is working it can show the swing of the boat around the anchor.

 

[Zephyrs Aura]

Celestial Nav

Hello, Celestaire has many books, calculators, and other celestial navigation items. Their website is listed below. There are many good celestial nav websites also. Celestial Navigation Net is a good place to start. http://www.celestialnavigation.net/ Celestial nav is fairly easy if you use a computer or calculator to find the line of position. If I don't have a calculator I prefer to use the S table to calculate the line of position. It eliminates the need for the HO-229 or HO-249 sight reduction tables.It does take a little practice to be able to get an accurate sight and it is far better to get someone to show you how than to try to figure it out on your own.

 

[Ted]

So the winner is? GPS?

Thanks fot the reply comments.Celestial, Loran and GPS all seem to have their issues. I'm getting the idea that GPS is by far the way to go. If you are at sea and there is cloud cover celestial is a no go. Loran is not compatible when you are out or range of a radio transmitter. GPS will work anyhwere in the world with the knowledge that there are some consistency issues.Is that what most here believe is ture.Further comments welcome.Thanks

 

[Peter]

Loran vs GPS va CN

Loran is old technology, just like Celestial. That said, both can be useful if GPS takes a dump. Loran is good only in certain areas of the globe, usually within afew hundred miles of land, and even then can be misleading in some specific areas where the "TDs" are intersect at wierd angles. and you can't even easily find a Loran unit to buy anymore. You must have an accurate timepice for CelNav. (And BTW, the clocks in GPS are among the most accurate we laypersons have access to.) You don't need stars to get lat/long if you have that good clock. Noonsite can tell you longitude as well as latitude with an accurate measure of the difference between local time and GMT.Getting accurate sites is the most difficult if you don't do it often. Like they say, PRACTICE, PRACTICE, PRACTICE. and with no real NEED for celestial, not many do.Celestial is really valuable only: 1) you're far offshore, 2) if ALL your GPS's are down (at $100/ea., I carry several), 3) if you keep in practice, and 4) if it interests you.Which means number 4 is likely what decides if you do or don't...

 

[Don on JCat Key West]

Celestial/GPS/LORAN/RDF

Celestial requires good sighting-aiming, current data tables and simple math. Gets you within sight of land.GPS requires a receiver, etc. Gives you instant location (within 100 feet) that you can plot on a chart/map or use with a computer, in blackout conditions. We use our handheld on hiking trips all the time.LORAN (system upgraded recently) requires receiver, etc. Gives instant location (within 1/2 mile) and the ability to return to a pre-recorded site (lobster hole) within a boatlength, in blackout conditions.RDF requires special radio that can be aimed at a beacon, overlaid chart with beacons identified, skill, etc. (similar to a transponder in an airplane). Accuracy similar to Celestial, in blackout conditions.First, understand coastal navigation, then supplement with GPS/LORAN.

 

[Didereaux]

Peter, you probably shouldn't...

Peter you probably shouldn't be commenting on cel-nav matters. You said,"Noonsite can tell you longitude as well as latitude with an accurate measure of the difference between local time and GMT." It should be pointed out that if you knew your precise local time you wouldn't need cel-nav, but you are moving, therefor your clock cannot keep precise local time... You set your chonometer(a decent digital watch) to precise GMT, then you take your 'shots' and calculate your precise longitude(which of course gives you the local time). I suggest you do all your boating navigation at the yacht club bar, you probably do anyway...but whatever else do not give advise on the subject, you do not know what you are talking about.sheesh!

 

[Franklin]

Didereaux

Sounds like a plan. Are you in the owner's directory?

 

[Didereaux]

Frank, I am at ....

Frank, I hate to put real phone numbers and such on the web email didereaux(-at-)email(-dot-)com and I can send it direct. I am at W7, Legend Point, ask for Monte or stop by the Boaters Retail Shop above Blackburns and tell Paul you need to get in touch with Monte. I hate to put real phone numbers and such on the web.... or email didereaux(-at-)email(-dot-)com and I can send it direct.Looking forward to it.

 

[Scott]

I like that one in #12, Ross!

It reminds me of a story I once heard ...A man, who was out standing in his field, happened to look up one fine day and discovered that another man in a balloon was descending to have a conversation with him."Excuse me, Sir! The man called down, we have been up in this balloon for over 5 hours, and we are looking for the Merriweather's house in Fairfield Subdivision. Can you please direct me?The man below, who always knew exactly where he was at any given time responded, "you are at latitude North 40 degrees 40 minutes 58 seconds and Longitude West 74 degrees 43 minutes 44 seconds. Your elevation is approximately 340 feet above sea level and the breeze is causing you to drift at about 4 mph in a southeasterly direction on a bearing of about 120 degrees. I am afraid you've missed your target by approximately 15 miles."The man in the balloon, called down once more, "Sir, you must be an engineer!".The man below was momentarily startled ... "Yes, I am, but how did you know?The man in the balloon said, "you have given me very precise information, and I am sure it is completely accurate, but I still don't know how to get to my friends house and you have been absolutely no help whatsoever!"The man, who was outstanding in his field responded, "and you, Sir, must be a manager".The balloon man called down, "Yes, how did you know?"The Engineer responded, "You don't know where you are, you don't know where you came from, and you don't know where you are going, but somehow you've managed to make your problem my problem!"

 

[Ross]

From all

that I have read GPS is much more accurate than our ability plot our position. Elsewhere in this forum I pointed out that with the 1:80000 scale a .5 mm pencil mark is 40 meters or about 130 feet. This means that the needle point on your dividers is larger than your boat. In addition Loran is in the process of being phased out. Celestial is considered an esential backup if you are going far. I have read about people that crossed the Atlantic without compass relying on contrails from airliners to point the way.

 

[Ross]

Scott it

seems to happen that way. I have a nieghbor that complains because I sometimes park on the street. The street is twenty-eight feet wide but his driving ability is such that he needs the whole street to get out of his driveway. He can drive in alright but he can't back out.)

 

[Rick Webb]

Who Needs Any of It

"If you get lost just pull in somwhere and ask for directions." Y'all remember that part right?

 

[BobW]

Plastic sextant and CN book on my Christmas list

When the lightning hits halfway to Hawaii or wherever, I'd like to still be able to get there, not the Asian land mass.Cheers,Bobs/v X SAIL R 8

 

[Ross]

look at

Davis for plotting sheets and work sheets. Makes practice much easier and more fun.

 

[abe]

It appears to me that alot of planes never would

have been lost in the Bermuda Triangle if they had GPS in the old days....so I vote for GPS and back up batteries for the back up hand held unit. Seriously, when I have more time I like to learn about celestial navigation. It makes sailing more fun than using todays techonlogies.

 

[Craig522]

Didereaux - a question

Now don't attack me for this, since I am admittedly a novice at celestial navigation, and I'm just asking. I'm wondering if it is possible to determine both lat and long with a noonsite in following way:1. assume you're more or less stationary (you know you're near noon, as you can tell the Sun is near it's peak in the sky, so you heave to, or whatever)2. take a series of Sun altitude sights at 5 minute intervals, and note the altitudes along with the GMT from your chronometer. 3. By looking at the data, you can see when the Sun's altitude was at it's peak and thus when it was "local noon". Since you wrote it down, you know the GMT time at that local noon.3. Couldn't you use the time differential between local noon and GMT to get the east/west location, and the Sun's peak altitude to get the north/south location?I understand this wouldn't be very practical for coastal navigation, but wouldn't it work to figure out generally where you are on the ocean in a pinch?Craig

 

[Garry @ S/V TASHTEGO]

For Craig

Craig,Diderot is wrong and your are right. The picking of the time of local noon is a little difficult but the error is not great (max. of 1 mile for 4 sec. of error in time).By the way, another easy sight reduction is available in polar waters. By using the pole as the AP the azimuth is South (or North at the South Pole) along the GHA of the body and the intercept (measured from the pole) is the difference between the Ho and the Declination. Easy!For fun see the photo of USCGC HEALY at the North Pole on 12 Sept. '05 with yours truly in the foreground. It is not often that you can walk around on the ocean and take a photo of the ship you are travelling in.

 

[Garry@S/V TASHTEGO]

Photo

Sorry, it was too big. Here it is reduced.