|Topic Review (Newest First)|
|10-03-2006 12:49 AM|
|camaraderie||HelloS...thanks for the support on this again. We're not gonna convince anyone here so I'm gonna drop out of the discussion at this point having said my piece. 90%+ of the people cruising today have no sextant and Darwin is ready for any who choose to do it with sextant alone. If someone wants to do it with both, all they have to worry about is rust on their expensive paperweight. I'd much rather go to sea with 3 GPS's than a GPS and a sextant. See ya on another thread.|
|10-02-2006 04:41 PM|
I'd say the key phrase to that entire article is "Charged particles from solar flares also produce intense bursts of radio noise,"
In other words, noise bursts may knock out your receiver for several seconds or several hours. The same way that a cloudy day will knock out your sextant. But GPS has been around more than 11 years, the problem is neither unknown nor unanticipated, and as long as you are not making aircraft landings during a noise burst, you'll probably have no problems.
Earlier this or last year, there was frantic talk that the world was going to end due to some intense solar flares, that cell phones would be killed, GPS satellites would be killed, tv and powerline networks would overload....Yeah, solar flares have come and gone before and yes, they really could wipe all life off the planet. So far, the news has mainly been focused on selling itself.
|10-02-2006 04:24 PM|
I'd like to point out an article that recently came out. It is readable here.
I'll quote the relavant part from it:
|10-02-2006 01:51 PM|
Cameraderie, any really good Real Navigator (like a Polynesian or Viking) would call your sextant a overly complex unreliable newfangled nonsense, the same way you'd look at a sextant.
You might not find Bermuda or Hawaii (unless you had an am/fm radio onboard and they were still broadcasting) after some despot caused the GPS system to be shut down, but you'd certainly find a coastline and then be able to make your way home without a sextant. Heck, you can see the nighttime skyglow from any major coastal city out at sea before you can see the coast in daytime.
To justify a sextant on the concept that the GPS system might be shut down for the end of the world, is pushing the concept a bit. If the world ends, you'll probably be safe staying at sea anyhow.
Celnav today makes a fine brain sharpener. A fine hobby, just like chess. But the same $300 that will buy a used low-end metal sextant, will buy two GPSes plus rechargeable batteries and a solar charger plus a brick of AA cells that can give you power for daily fixes for six months by themselves.
Drop the sextant, and you've got trash. Drop the GPS, and you've got the spare. With more spares at $100 each.
Celnav is an anachronism today. Like a horse and buggy, it still may be the best tool for a job--may be, some times. And it might make a nice change to take the horse and buggy out for a picnic in the country.
But in practical terms? Expensive, fragile, bulky, unreliable (use it during a 48-hour overcast, go ahead) and requiring a trained user and auxiliary materials.
Nice if you can afford it as a luxury and a hobby, but of little practical OR potential value these days. And that's from someone who has owned them and enjoyed using them.
|10-02-2006 08:00 AM|
|sailingdog||Last I checked, the Russian navy wasn't hunting my nuclear missile carrying sailboat.|
|10-01-2006 11:47 PM|
Methinks I've pricked a boil here somehow. There are certainly differences in philosophy of what constitutes responsible navigation procedures. The US Navy is entitled to theirs. They've made mistakes before and will again. The landing ay Inchon was delayed three months because somebody decided they didn't need all those wooden hulled mine sweepers from WW II. That's the navy. You say government, I think post office. Because I hand my shipmate a GPS doesn't make him a navigator. And, every ocean going vessel out there now has a GPS. It's too fast, accurate, reliable, cost effective, and relatively trouble free to otherwise. Radar was the same. The average non naval vessel does not have the government behind it to fly out spare parts. When a generator spike frys all your electronic gear the mate on watch has his chart with his fixes plotted. He doesn't lose his set/drift data, it's right there on the chart table. If computers, of all ilks, are so wonderful (and they are) why does everyone request a hard copy of any important information that they do not wish to lose? Sure, we use GPS but we've got a sextant and a chronometer standing by. Coast Guard board of inquiries take a dim view of groundings based on a lack of navigational ability. Every ship still slides down the ways with a sextant and two chronometers on it. Lloyd's and any other marine insurance firm won't have it any other way. Back in the seventies, it was accepted naval warfare planning that, in the event of war with the USSR, the first thing that would be done is the shut down of the Transit system(NNSS-navy navigational sat. system) and that ships would run with no electronic emissions as well. No radar, radio, etc... Now if that wack job in N. Korea decides to launch a better missile, and we figure he's using GPS to guide it, how long do you think befere the plug gets pulled? Now, getting back to Argos original question I think that, contemplating an ocean crossing he has an entirely reasonable approach. It's simple, reliable, and doesn"t cost that much when you consider the components are good for more than a lifetime of use. If you would rather use redundancy of GPS receivers (and a good lead line) that's fine. Me, I can't keep a cellphone for more than two years without it getting wet or damaged somehow. I've crossed alot of oceans, and in my opinion, the test of any piece of equipment is it's reliability and what are we going to do if it fails. And to be honest, in a forum such as this, I suspect there are alot more people relying on a $100 widget to get them back home than what I'd wish. And real ocean navigators do pull the old hambone out from time to time just to keep from getting rusty, if not for the joy they get out of seeing that beautiful pinwheel on their chart. And why would anyone cross an ocean in a sailboat anyway, when there are alot more reliable, modern, mechanical, and electronicly equipped ways of doing so? But, fair winds and following seas to sir. "Curmudgeon"
|10-01-2006 11:15 PM|
I have a bit of a knot in my shorts. I learned celestial from a book by Bruce Paulk using a cheap $25 sextant and artificial horizon in the backyard. I'll probably go the Astra IIB route before we shove off from shore along with paper charts and other non-high tech items for when Murphy's law kicks in and I need to find out where I'm not.
|10-01-2006 09:42 PM|
"But then, some people don't see the need for paper charts either!"
Yeah...like the US Navy again!
As the Institute of Navigation stated in 1999:
With the advent of GPS and other high-performance electronic satellite navigation systems that are fast and inexpensive, require no operator effort, and give a continuous read-out of position to within a few meters, using a sextant to take the stars is surely obsolete. Perhaps the death knell for celestial navigation was sounded in May 1998 when the United States Naval Academy announced it was discontinuing a course on celestial navigation and the use of the sextant that has been taught since the Academy's founding in 1845. Sooner or later, air and nautical almanacs will no longer be published and there will no longer be a need for hand-held instruments for taking the stars." Somewhat sadly, this may mean the demise of art in navigation.
If you do celestial as a pleasure and an art...more power to you. If you think of it as an essential skill for a navigator today...you are a curmudgeon with your shorts in a knot!
|10-01-2006 07:16 PM|
One other thing... Tayama and Plath make beautiful instruments, but are four times the price of a Astra IIB, which is a pretty decent, if relatively inexpensive sextant. About $500 retail, less if on sale. The plastic ones can be problematic as they can warp if left in the sun, and the warping is often not very noticeable but will throw your readings way off. Tania Aebi, of Varuna fame, had that problem.
The sextant handbook is a very good book on how to adjust and calibrate a sextant for side error, index error, etc.
Lots of good books on sextant use out there too. Blewitt's Celestial navigation for Yatchsmen is an old fallback. The Complete Celestial Navigator is another good one.
|10-01-2006 07:12 PM|
Navigation has been a "collateral" duty for an officer in the navy for at least the last thirty years. That's hardly a condemnation of celestial navigation-more an indictment of the navy. Where's Harry Weems when you need him? Two mile accuracy is adequate for any off-shore navigation system and, in fact, that is the standard. If you need greater accuracy you are probably in a piloting situation. And I would not classify two miles as a good observation in good conditions. With a cheap sextant or poor conditions, ie... rolling deck underfoot, not bad, but I wouldn't consider it my best effort. Refraction is a zero sum game with a marine sextant as horizon and sky glass experience the same and cancell. A bubble sextant is different and those correction factors are included in the air navigation tables. The colregs require decision-making not be done based on scanty information, especially scanty radar information. I,m sure that you've heard of radar assisted collisions. The important point being that the prudent navigator is required to utilize all means of navigation (that's why the radar is on even in perfect visibility) and you do not know there is an error in an electronic instrument unless you compare it to some other reference. All of the maritime academies still teach celestial navigation and the USCG still tests it for licensing (90% is passing grade) and that's why shipowners entrust 150 million dollar ships to them. Use every tool you have, but don't tell me that GPS has eliminated the need for celestial navigation. But then, some people don't see the need for paper charts either!
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