Old Tech is New Again

After having stopped teaching Celestial Navigation for about 10 years, the U.S. Naval Academy has reinstated it. Apparently the Coast Guard Academy also stopped teaching it at about the same time, but the Merchant Marine Academy never stopped teaching it.

http://www.capitalgazette.com/news/naval...1009-story.html

Smart move on the NAVY's part. Celestial is battery free and EMP proof. I used it regularly in the N. Atlantic & Caribbean Sea until the mid 80's.

The Navy should also reinstall their HF Transceivers as well.

A few years back I was thinking about getting a sailboat and the idea of getting lost due to a GPS issue convinced me to get a sextant. I ended up getting two, a Davis Mark 3 and a Davis Mark 25. The Mark 3 is a lightweight plastic training sextant that works quite well; the Mark 25 reminds me of the old brass models that are outrageously expensive, but it's lighter in weight, has great optics and is made of a stable plastic.

Remembering my celestial nav course from decades back, I really hated the look-up tables and math to complete a site reduction to get a single line of position from a star/moon/sun sighting. An app on my iPhone & iPad made that problem go away. "Celestial by Navimatics" does the math after you input the data.

Then all you need is to know is which celestial body you are shooting -- sun, moon or one of the many stars used for navigation. There are a few good apps for that too -- Sky Guide, Star Chart, Star Walk ... Then there's AstroNav which combines the sextant with the math. Cool... For some reason it's no longer available for the iPhone.

Never did get the boat....

I used to shoot only those navigable stars that were apart of a constellation. That eliminated shooting the wrong star in error. 10 good star shots gave me 10 good LOP's.

In "The Martian," the main character (Mark Watney)had to construct a primitive sextant and use celestial navigation while he was trapped on Mars!

That´s only true, when you use a mechanical watch. Quartz watches with solar panels at least are not so dependend on batterie (6 month reserve without light and 10 years of service life should cover most scenarios).


It might be a good idea to do it while there still are plenty of competent operators around.

Good point regarding time. Quartz watches need a battery, but many also need a regular update from a time source like WWV. Many watches are sold as atomic time pieces, but really they are mediocre timepieces with a small radio receiver designed to give them a daily time tweak to give the illusion of a precision timepiece. If the GPS signal is shut down, who's to say that WWV doesn't also get turned off. As time errors increase, accuracy of a celestial fix is reduced.

If you have a watch that relies on a radio signal for accurate timekeeping, lack of this signal may be worked around (on land) by looking up in tables the time of sunrise or sunset and comparing this with the time as told by the watch.

The watch may then be corrected, or if it has no facility for so doing, simply remember that it be say 6 minutes slow.

In time you may find that such a watch looses say 30 seconds a week and this correction may be applied if making a sea voyage.

If making an ocean crossing after TSHTF, then it would be sensible to carry a number of timepieces, and a record of how many seconds a week each one gains or looses.
The time of day for navigational purposes may be taken as the average of several timepieces, after correcting for known errors.

A top quality mechanical watch should keep excellent time, and several should be on board an ocean going vessel.

If TSHTF and you don't have a first quality mechanical watch, then remember that in the early stages of an emergency that you should be able to buy one cheaply as people sell or pawn them for other supplies.

You cannot use the sun's rise/set tables to correct your clock when moving a lot, they are also affected by the weather, changing the atmospheric refraction. But I believe any modern electronic watch is precise enough within a 6 month period of time (one could measure the drift precisely enough beforehand to correct for that anyway, if absolutely necessary, but sextant's measurements might be not precise enough to be affected by the modern watch pace drift fluctuations). Then, every 6 month you could observe the Sun around equinox in order to figure if your clock's correction must be adjusted.

Shoot a daily noon sight and you can determine your Longitude and adjust your time correction table for your chronometer every sunny day.

That's a common misconception. See here: http://www.idialstars.com/eot.htm

Low-tech backups as a good idea:

Seeing stars, again: Naval Academy reinstates celestial navigation

Allready another thread on the subject: http://forums.equipped.org/ubbthreads.php?ubb=showflat&Number=277030&gonew=1#UNREAD

I merged the threads. Carry on.


chaosmagnet

I'm glad. Having the Navy teach Celestial navigation is like the Army teaching their land navigation course with a standard compass. In practice, I'm sure a standard compass is rarely used but if the GPS is somehow out of commission, it is good to know how to navigate without one

So, when do they re-implement the original technology for determining speed across the water?

Most ships are already equipped with piton type instruments similar to what aircraft utilize.

Yep, Pitot tube. I didn't know that ships had pitot type systems. Thanks.

The Engineers had to lower ours down once we got into i certain minimum depth of water. It would always be retracted before we got into shallow waters.

Sorry guys, I was going for knots on a rope.

I know but I ignore the obvious most times.

Check out this NPR story...

http://www.npr.org/2016/02/22/467210492/u-s-navy-brings-back-navigation-by-the-stars-for-officers

I've never been trained on determining ones position using just a sextant and a clock, but I'm given to understand that it builds character.

There is already a thread on this: Old Tech is New Again

Whoops, I should have caught that. Thank you. Merging threads.



chaosmagnet

I had a course on it in NROTC but being far inland we didn't take sightings. Net result was that we could recognize a sextant and knew that one needed a really thick book of numbers to go with it - and an accurate clock.

Later, once aboard ship, the only contact with the sextant was to know where it was kept and maybe be invited to help inventory it once a year.

Navy Navsat was the predecessor to GPS and it worked faster and more easily than celestial nav - especially for a submarine.

GPS is near magical now. But can be turned off at any time. So old school skills could prove useful.
Still, taking sightings from a submerged submarine???? I hope not.

I'd have thought using a periscope for celestial sightings would be fairly straight forward. Just another sign of how reliant we have become on "tech" and more justification to bring back celestial.

For starters- Scope course is parallel to the waves so you don't get sucked up and broach. In a round bottom boat.

There might have been special scopes for early boats but I've spent a lot of time dancing with the one-eyed lady and it's difficult to keep a contact in sight nevermind getting a precise elevation angle.....

Probably WWII boats used celestial but they would have a sextant because they were really just surface craft that could disappear for awhile.

I can recall reading some documentary about WWII subs. They indeed surfaced often to take celestial bearings. Now they just surfacing a tiny floating antenna on a cable. However, with the modern tech it's not that hard to implement either a gyroscopic sighting aid integrated in the periscope, or even a completely computerized celestial navigation system similar to those pinpointing the spacecrafts precise landing after years of navigating in space. By the way, Mars rovers were using celestial navigation for their ground operations long before the nav-sats started orbiting Mars. They still do actually, as the MGPS constellation is not thick enough yet.

They used a sextant as the alternatives where even less accurate when there was no landmark in sight. The subs surfaced to use the sextant. That was some disadvantage especially after the allied forces became better hunting them.
That´s also featured in the movie "Das Boot". Two submarines met in a storm and the skippers come to the conclusion that they are nowhere near the coordinates they were supposed to be. The reason was a longer period of bad weather which did not allow to get a fix with the sextant.

in 1980, when gps technology was financially beyond the reach of the average sailor, i sailed across the atlantic. from gibraltar to the madeira islands to the british virgin islands. we used a plastic sextant, a shortwave radio tuned to the bbc who, at that time, counted down the seconds to every g.m.t. hour, the aforementioned books of declination, and did the math by hand. we hit the anegada passage right on the money after a crossing of 40 days.

yes, it builds character. one hand for the boat and one hand for you is challenging when it takes two hands to use the sextant, never mind the radio.

I have taken exactly one sextant reading in my life. I placed our position near Santa Cruz Island, which was true enough, but i plotted us on the south side, while it was apparent that we were on the north side... MY GPS does a whole lot better, even on a bad day.

A celestial position accurate within 20nm of your actual position is considered a good fix upon the open ocean. At my peak (1983) my position accuracy was 5nm consistently.

Sure, anything is possible but the ship I was on did not have any of that stuff. You use the stuff you have, not what is technologically possible. Installing a dedicated scope for celestial nav seems highly unlikely.

Navy Navsat was hot stuff before GPS came along. But when we deployed at least one time a LORAN receiver was added because it was old, proven technology that was more available.

I've read stories of many military platforms (aircraft mostly) being saved by crew personal purchase hand-held GPS because the standard equipment in the platform did not yet include GPS (procurement/cost/needs of the service etc can delay sensible upgrades)

Thank you very much! That is nice to know. I was off by about ten NM as I recall....