More Celnav stuff.

[HenryC]

The articles on celestial navigation listed on this section (they have titles like Celnav zero, celnav one, and so on), have been updated. I have reworked the example sight reduction so it can be re-done using the 2015 Nautical Almanac, which is now available for sale. 

I have used the Naval Observatory website computer

http://aa.usno.navy.mil/data/docs/celnavtable.php

to generate data for a Sun line taken from  an arbitrary location and time, Lat N26d 30' and Lon W80d 30' on the morning of Jan 15, 2015. This will give you guys plenty of time to practice up with the current issue of the Almanac. 

The way this works, I use the USNO app to tell me what my sextant SHOULD read if I were at that time and place.  I then use the sight reduction procedure to determine what the sextant will read from an arbitrary Assumed Position at 26N, 80W, about 40 miles away from my "true", but unknown, location.  When I plot the Line of Position, I can tell how well I did the calculation by seeing how close the LOP comes to the (presumably unknown) position.  I missed it by about a mile, which is not bad, considering the usual sources of error, round-off, plotting inaccuracy, etc.
Of course, this is all done mathematically.  I don't even know if my test location at 26d 30'N and 80d 30W is on the water or not!  There's a lot of places where I might have screwed up, so check my work!

Please feel free to contact me if you have any questions, or if you spot any errors or mistakes in my notes.  There is also a possibility I may have missed or forgotten something in the update, and I would appreciate it if anyone spots it that they let me know.

Good Luck.

[Ivo]

Thanks HenryC...just ordered the 2015 Almanac for study.

For those interested...nice youtube series on this subject.

http://www.youtube.com/playlist?list=PLah9ocjQNN0Zr7-oKE58wTzXE4XaQU64E

[HenryC]

GPS has made the sextant obsolete, and Youtube has made books about CelNav obsolete.

I only watched the first few episodes, but it is clear that this is an excellent intro to the subject, and I definitely recommend it.  The navigator obviously knows his stuff, both as a navigator, and as a teacher and film maker.  And he has an Astra sextant just like mine!