Celestial Navigation

[CruiseAlong]

Yes I can do it for multiple people. I would like to limit to 10 or less.
I wasn't kidding about the bucket of water. If you can not see the ocean horizon to the south we will use a real pail of water which is protected from wind wavelets. Other than that you have to have a sextant "bubble sight" which takes the place of the horizon. The Davis artifical horizon is just that (a tray of water with a plastic wind cover).....A small lake does not cut it because of the water reflection distrubance and its horizon is not far enough away (15-18 miles). There is an available correction for a short horizon but you have to know the distance to the other shore...But the only basic requirement is that you can see the sun overhead a couple of hours before high noon until a couple of hours after high noon and have your bucket of water.. OK is a great location ..... Drop me an email at darenius@verizon.net if you are interested and I will start the participant count...Dana

[tartansailor]

Barf,
Bubble sextants are useless at sea.
Use a pan of real dirty crank case oil in a container with high sides so the wind will not roil the surface.
Dick

[CruiseAlong]

As I have been researching web site locations for celestial navigation form information, I came across the following locations which may interest others on this board. Copy and Paste location into your Web Address window


Maritime Safety Information PageHere you can download the entire American Practical Navigator (Bowditch), Sight Reduction Tables for Celestial Navigation HO229 or HO249 and Navigational Calculators including "short horizon" correction.

http://www.nga.mil/portal/site/maritime ... d73927a759


On LIne AlmanacProvides three day daily pages for stars, sun, etc. Type in your first date. Enough information to perform basic celestial navigation. Printable.
http://www.tecepe.com.br/scripts/AlmanacPagesISAPI.isa

For Checking Your Watch Time...
http://tycho.usno.navy.mil/what.html

Altitude and Dip Correction Table
http://www.nao.rl.ac.uk/data/na2003/bookmark03.pdf

Celestial Navigation Line of Position Calculator
http://aa.usno.navy.mil/data/docs/celnavtable.html

[Dan & Pat]

Dana,

I've been doing a little shopping around, and have found 1978 and 1979 editions of the Air Navigation Tables Volume 1 for a reasonable price. Should I be concerned because they're almost 30 years old? Is this the kind of data that becomes off by a little bit every year, or will these do?

Dan

[CruiseAlong]

Volume 1 is for selected stars
Volume 2 is for latitudes 0-40 degrees
Volume 3 is for latitudes 39-89 degrees

You would want Volumes 2 or 3 and not 1 or 2 as I mentioned above.
Sorry it was a mind slip....right titles, wrong volume numbers.

No, volumes 2 and 3 do not go out of date. They solve a spherical triangle problem and that does not change.

You saw that these volumes are available for free in PDF format asa listed above from the Martime Safety Information web page? Also if you can not find the volumes but have a calculator which can do sine, cosine and inverse sine functions, there is a simple formula for calculating the expected angle height (Hc) and the azimith (bearing). Would be glad to provide you with the equation.
Dana

[tartansailor]

Don't buy. See Bowditch pp.2012 Sight Reduction Tables for Air Navigation (Pub. No. 249) line 20

Progressive changes in the coordinates affecting the tabulated data necessitate re
computation approximately five year intervals in order to reduce the effects of this source of cumulative error. The volume for 1980.0 will replace the volume for epoch 1975.0

I do not like to make these types of corrections, especially on a public forum, so could you please consider taking formal classes. Most Celestial Navigators are using H.O. 229, and the die hards and the British Navy are using the Nautical Almanac Sight Reduction Method.

I use the latter.

The calculator method is great for the class room, but imagine what just (1) salt spray will do. Be sure to encase your calculator in a special water tight case so you can still press the right button.

Dick

[Dan & Pat]

Just wanted to post that I'm bidding on a Davis 25 sextant on e-bay. I know there are a few of you who are getting 'into' this now so if anyone else from this site is bidding against me, let me know. There's no sense in bidding this thing way up against a friend (fellow CD'er ).

Dan

[Joe CD MS 300]

....restraint of trade violation. Where is the Justice Department when you need them? I won't be bidding, I'm still trying to figure all the bells and whistles on my chartplotter.

[Didereaux]

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... &rd=1&rd=1

I see one more day on this one as well, a Davis 25.

g'Luk

[Dan & Pat]

Someone named Montephillips is bidding on that one... Hmmm wonder who that might be . I'm dano1851 on e-bay just for the record..

[Didereaux]

heheh
I had put that bid in on the day it was placed. It will(has ) go for a wee bit more...probably around a $100 or so. They seem to hold at about half new price. By the way a complete rebuild kit for those(less mirrors of course) is only $8 from Davis, that includes the mirror clips and screws.

I really do like those sextants, but of the 'hard' ones the best value, if you can find one, is the SNO-T Russian sextant vintage 1970ish. Excellent Zeiss optics and very precise, they can actually be read down to less than 10 seconds arc, although that is nearly an impossibillity to achieve such an accurate shot. Thye used to go for a little under $200, but the ones lately that I have come across are higher.

Anywho, if you do not get one this go around let me know I will keep an eye open for you.

[Bob L]

One way to learn celestial navigation is to take a class. If you're lucky enough to live near a planetarium (like the Adler in Chicago), you can usually find a cn class there.

For what it's worth, I used to fly on an airborne observatory and we needed to convert the azimuth and elevation of an object to celestial coordinates (Right Ascension and Declination). I wrote a program to do that (on an old HP67 for any geezers out there). In doing so, I realized that with a few minor changes (altitude corrections, etc), it could be used to quickly calculate latitude and longitude from a measurement of a known object. Of course that meant accurately measuring the azimuth of the object, which, on a moving platform, could lead to larger errors than the sighting might. Trying it on dry land with a small telescope and a compass, I could get lat, long calculations accurate to 1/2 mile.

[Dan & Pat]

Dana,

I won the auction for the Davis 25 Sextant, and it should be arriving shortly after the Thanksgiving Holiday. I'll PM you when it arrives and we'll set up the tutoring.

Meanwhile, I've been going through the "nutshell" book and am learning some of the terms and abbreviations. Will Be In Touch!

Dan