New Life for Old Pub 249 Vol. 1

An out of date Pub 249 vol. #1 Air Navigation (selected stars) is still extremely useful for general star finding, selecting optimal stars for twilight observations, and determining star azimuths to the nearest degree. Combine Pub 249 (to tabulate selected star azimuths) with a scientific calculator (to calculate altitude from a DR assumed position) and save a great deal of calculator button pushing with no loss of precision. A must try on your next round of stars.

Celestial Navigation by TI-36X Pro

The TI-36X Pro is an excellent value calculator for celestial navigation sight reduction. Enter the formula for calculating altitude into the NUM-SOLVE function then follow the prompts for variable entries.

Calculated altitude formula:
a=ArcSin(Cos(x)Cos(d)Cos(t) ± Sin(x)Sin(d))

Variables:
x= Latitude
d= Declination
t= Meridian Angle
a=Calculated Altitude

Use the OP function to solve for azimuth Z.

Key the SET OP function and enter the formula:
ArcSin(Cos(d)Sin(t)/Cos(a))

Once (a) is solved in NUM-SOLVE then azimuth Z can quickly be solved in the OP function with one key push.

Convert calculated altitude (a) into degrees minutes and seconds using the MATH menu DMS6 or multiply degree fraction by 60 to get minutes and tenths.

New Deck Shoe Break-in

Shorten the break-in time for a new pair of leather deck shoes using liquid lanolin rubbed onto the bare foot before inserting into the shoe naked and worn for a day. This will soften the leather inner sole so that it will mold to the bottom of the foot. A comfortable deck shoe equals a happy sailor :-)

The Elegant Amplitude

The amplitude is perhaps the most elegant way to determine compass deviation and gyro error*. Use Bowditch table #27 (4 pages ) or a pocket calculator and the formula:

INV SIN [ SIN (Declination) / COS (Latitude)]

Apply the result to due East (90) or West (270) in the direction of the elevated pole when Latitude and Declination are of the same name (away if contrary). Take observations when the Sun's lower limb is 2/3 of a diameter above the visible horizon.

Tip- Keep a photo copy of Bowditch table #27 with the current years Nautical Almanac.

*Checking the compass/gyro at sea requires a celestial solution. Until the GPS compass becomes commercially affordable navigators will need to keep their celestial compass checking skills sharp.

Companionway Step Brace

Older companionway steps are prone to splitting and loosening over time. A preemptive plywood stiffener and support bracket will aid in preventing step collapse and possible injury. Be sure to drill the appropriate sized pilot holes to accommodate the stainless wood screws.

Hybrid Ex-Meridian Method

Bowditch table 29 value (a) combined with a slide rule or calculator using the formula (a)(t^2)/60 generates a correction in minutes of arc to be added to the altitude (Ho) of an observation made within 30 minutes time of meridional passage. The sum is then solved as a standard meridional passage observation to get the Latitude [Lat.=90°- (Ho+ corr).~Dec.]. This hybrid method saves page turning, interpolation, and button pushing while adding precision.

HandiTak Chart Corners

A pea sized ball of HandiTak is just right for securing chart corners down on the chart table. This will put an end to the sliding of charts onto the deck. HandiTak generally will not rip a chart when removed but just in case tape the corners with clear packing tape.