Sunday, July 26, 2015

Classic Trig Log Sight Reduction by Ageton

Classic trig log sight reduction can be done using the Ageton Pub 211 table in lieu of trig log sin cos functions. This facilitates the log summing process, shortens reduction time, and lowers the chances of arithimetic errors. Calculating the prime vertical and amplitude can also be done by Ageton table.

Tuesday, June 9, 2015

Modern Haversine Sight Reduction

The cosine haversine Doniol sight reduction formula can be written as an all haversines formula to create the Modern Haversine Method of sight reduction. Only a single haversine table is needed and there are no special case rules.


hvZD = n+[1-(n+m)](a)

Same Name
n = hv (L-d)
m = hv (L+d)

Contrary Name
n = hv (L+d)
m = hv (L-d)

L = Latitude
d = Declination
t = Meridian Angle
a = hv(t)
hv = Haversine
ZD = Zenith Distance
Hc = (90 - ZD) Calculated Altitude

Precision is 1' when done longhand to 4 places using natural haversines (see attached example). Azimuth is quickly done using the Ix graph (attached)

Tuesday, May 5, 2015

Pocket Slide Rule

The pocket K&E Doric offers serious faster than a trig calculator navigation calculating power for time, speed, distance, eta, prime vertical, amplitude, and the radius of a horizontal sextant angle circle of position.

Circle of Position Radius Formula:

.5 (A to B)/Sin horizonal sextant angle = the radius of the circle of position. A, B, and radius are in nautical miles.

Monday, January 5, 2015

Marine Log Book Pen

The Zebra F-701 can be refilled with a Fisher cartridge to create the perfect all weather log book pen for on the water use. Completing the cartridge swap requires removing the plastic tip insert with a paper clip which allows the Fisher cartridge to drop in without any further modifications. The barrel knurling can be coated or taped to prevent pocket chafe.