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.