Thursday, June 25, 2009

Navigators Mate

The Palm Centro smart phone is quite the navigators mate in the cockpit and at the chart table. When in port the phone provides NOAA weather from the internet. At sea the applications smartly deliver full celestial navigation , sailings, piloting, chronometer and tide functions. The bonus is a full media capability to document a voyage by photo, video, and audio. If boredom strikes in a calm then there are games and music features as well. Truely amazing!

Wednesday, June 10, 2009

Calculator Compass Check

Checking the magnetic compass at sea is a snap with the assistance of a pocket calculator and the azimuth formula

SIN azimuth = (COS declination x SIN meridian angle) / COS altitude

For the formula altitude use an estimated (hs) sun altitude by counting the solar diameters above the horizon and multiplying by 0.5 degrees. (hs) Altitudes above 3 degrees will require a sextant. Declination is easily retrieved from the Nautical Almanac. Meridian angle will require GHA from the Nautical Almanac and a DR longitude. Time should be to the second as per short wave time tick on frequency 5000, 10000, 15000, and 20000 kilohertz. Double check calculations with Pub. 249 tables.

The pictured calculator is a CANON F-710 which is an excellent value calculator for trig applications. Also recommended is a book CALCULATOR AFLOAT by H. H. Shufeldt