Considering these ideas of navigation.. What is your opnion on it?

[Adelie]

Originally Posted by CatNewBee

. . . .
Practically it would be the last resort in case anything fails, but it is very unlikely to happen. Even the US navy no longer teaches / uses sextants as fall back, and they still learn starting fire with dry sticks in survival drills.

The USNaval Academy recently started teaching Celestial Navigation again to officer candidates. They did so because they realized that there was no other backup in case of hot war or cyberwar. DoD interest in eLORAN has been somewhat renewed.
The USNavy never stopped teaching it to enlisted folks though actual practice in the field was up to commanding officers and thus was a bit spotty.
The USNA is teaching it again not so newly minted officers can do it themselves but so they can intelligently manage the enlisted folks who actually do it. The USNA is receiving help to reestablish the program from the Merchant Marine Academy which never stopped teaching CelNav. The USCG Academy never stopped teaching either.

[fernandosmooth]

Originally Posted by captwylie

My dads favorite shrimp recipe was simply fried shrimp. Dipped in milk and egg then then tossed in flour seasoned with salt and little red pepper. Fried in very hot oil and removed as soon as they float.

If there was an imaginary table with everyones posts about navigation, I would sweep right to the right all things, some would even fall to the floor but I would pick it up later then I would put your recipe in front of me right now.


I am not sure I am going to try celestial but I will try this shrimp. You can quote me on this later on.

[CatNewBee]

Don't get me wrong, I am considering to buy a nice old brass sextant and an universal almanach plus sin/cos tables to find the position just for fun during long passages and no fish-on, to keep me busy. This stuff is also very decorative. But I doubt I would ever need it to navigate an ocean.

[GrowleyMonster]

Originally Posted by Olddan1943

When one says, "Learn to navigate", does that mean using a sextant ?
If so, how many folks even own a sextant?
How many use it routinely to maintain their skill?
How many rely on their sextant as their primary source for navigation?

To begin with, keeping a good DR. Understanding your compass and bearings. Understanding the Mercator Projection and truly understanding the relationship between Latitude and Longitude. (HINT: You probably don't even though you think you do.) Knowing how to construct a plot sheet for your Latitude. Understanding the Rhumb Line and the Great Circle. Understanding the relationship between rectangular and polar coordinate systems. Understanding Set and Drift. And Leeway. There are a lot of things to learn before you even touch a sextant, things that can stand on their own without a sextant. Even celestial skills that do not require use of a sextant such as taking an amplitude or an azimuth for a compass check. Important stuff. This is the heart of Navigation, not manipulating a sextant, taking an observation, and doing something useful with it. BUT... the use of the sextant is not rocket science and you can learn with baby steps, and stop wherever you are comfortable. Just Latitude by LAN is very simple and very useful. Two centuries ago, the only thing the Navigator could be reasonably certain of was his Latitude, and they circled the globe with their rudimentary navigation skills.

IF one writes down their GPS position on their paper chart every 30 or 60 minutes just in case the GPS system goes down, shut off, or a lightning takes out all your electronics?

A VERY GOOD PRACTICE! But from that point you had better know how to do your own navigating, starting with keeping a good DR. If you had been doing that all long, you would know how much you can rely on your skills, and improve them through trial and error, practice and effort.

If lightening takes out all my navigation electronics at the same time my first thought would be "upgrade time", "hello insurance company?"

Nice. If you can communicate with your insurance company. But you still have to get to a port, even "any" port, safely. If you are a Navigator, you can do it. If you are not, it's a roll of the dice, a draw of a card. It is amazing how lucky some folks are, so maybe you are good to go!



The chances that you might ever be forced to rely on navigational skills is slim. Slim, but not nonexistent. You have two bilge pumps, right? I bet you have two pocketknives. You probably have an emergency tiller to steer your wheel steered boat. You probably have a spare for every sail you carry. If you dive, you have two second stage regs. Extra fire extinguisher. Two digital voltmeters. Backups. Redundancy. It makes a boat and those in it safer. You should have two ways to know where you are and how to get to somewhere else, too.

[GrowleyMonster]

Originally Posted by CatNewBee

Don't get me wrong, I am considering to buy a nice old brass sextant and an universal almanach plus sin/cos tables to find the position just for fun during long passages and no fish-on, to keep me busy. This stuff is also very decorative. But I doubt I would ever need it to navigate an ocean.

Very likely you won't "need" it. But it, and the knowledge to use it, is one of those things that it is better to feel stupid for having and not needing, than to feel stupid for needing and not having.


Watch out for those ebay "sextants" that are in truth only reasonably faithful replicas. If it is all brass and not enameled it is probably either 250 years old, or it is a knick knack only. Same goes for if it is listed for $69.95 or if it is coming from India and it is not a Plath or a Tamaya or Freiberger or similar. Your budget for a quality used sextant needs to start at $300 or so for a used Plath in good condition but needn't go over $800. Other options are a new Astra IIIB from www.celestaire.com, or a plastic Davis Mk25 from the same vendor, if you are okay with its shortcomings. A brand new Plath or Tamaya is a joy to posess and to use, but for most of us the cost is not money sensibly spent.



It is difficult to learn celestial navigation with a shoddy poor excuse for a sextant. Instrument error totally overshadows small computational errors, so you won't know if you are doing stuff right or not. If you have an instrument you can rely on, you will spot your errors and develop your skills.

[NevisDog]

Originally Posted by CatNewBee

Don't get me wrong, I am considering to buy a nice old brass sextant ...

Maybe look at a nice second-hand but slightly newer alloy sextant? Fabulous choice out there, so maybe do a little research first. The old brass ones are heavy and really only good for hanging on a wall nowadays.

[I sailed with some navy guys and they all agreed they were 'blown away' by how comfortable and easy to use they found my yacht sextant; young officer even achieved a zero intercept with his first attempt (very carefully executed) star sight using it - he was impressed! (So was I.) ]

[Olddan1943]

Growley, yup you are so correct.
I am told, the Power Boat Assoc has a course on navigating. I dont know how extensive it is.
Being able to determine where you are, via a sextant is so mystical and magic one might be deemed a witch LOL
The more one practices, the more faith you have in your own ability and impress those around you.

[Snowpetrel]

Writing down lat and long + compass course vs COG at regular intervals is also a very good practice. Comparing COG vs Compass course will give you a basic idea of compass error and any leeway or current effects.

I always like to play a game with crew called guess the days run. Each day at noon we would place bets on the 24 hour run. The noon GPS fix would be compared to the prevoius one and the closest person got a small reward. It was impressive how good a feeling you can get for how far you have gone. Typically before long we were usually all well within five to ten miles without any instruments. I guess you could add true course made good into this challenge.

The same thing can also be done on a watch by watch basis.

[Jammer]

Originally Posted by CatNewBee

A metal box is a Farraday cage, it is sufficient for any lightning voltage, except it melts down.

Where can I get me one of them zero-resistance electrically perfect metal boxes? I want one for my boat and a couple for the lab. It's just not as electrically quiet in my coffee can as I would like. Or in my fancy copper screen room, for that matter.

[Paul Elliott]

Originally Posted by Jammer

Where can I get me one of them zero-resistance electrically perfect metal boxes?

And it sure isn't an oven or a microwave. These may provide some protection from lightning-induced fields, but they are far from sealed. The door gaps in particular will let through a significant amount of RF energy. Microwave oven doors use quarter-wave gaps to block the RF energy, and this works well at the 2.4 GHz microwave frequency. However, it doesn't do much at other frequencies. Put a cordless phone in it and you can still make it ring. The energy from a lightning strike is very broadband, and a big one will still drive serious energy through a microwave (or any type) oven door-gaps.

[transmitterdan]

The best metal box for EMP is an old steel army ammo box that is vacuum drawn with no seams. The steel is magnetic and so has a strong dissipation effect on EMP. The lid is the only gap and the gap is small enough such that it does not allow the frequency range of EMP to enter. Most EMP energy is below 100MHz and the thin gap has a cutoff frequency much higher than that. The seal doesn't have to be perfect it just has to be good enough.

[CatNewBee]

Just buy a plastic sextant.

[GrowleyMonster]

Originally Posted by CatNewBee

Just buy a plastic sextant.

A viable option. I will say that the imprecision of a plastic sextant can possibly make learning Celestial slightly more difficult, but it is better than nothing and boats have indeed crossed oceans with these. The Davis Mk25 is the one I would recommend. Keep it out of direct sunlight as much as possible. You can get quite significant instrument errors both from long term exposure, and from just having it out in bright sunlight preparing to take a shot. Quality metal sextants do not give significant errors due to solar heating and expansion. At any rate, keep your sextant in its case when not in use.