Sunday, December 19, 2010

Symmedian Point

Shift a celestial navigation LOP triangular plot center slightly toward the short side (sides) for an improved probable position (symmedian point)

Thursday, December 2, 2010

Horizontal Sextant Angle Plot Made Easy

Make short work of plotting horizontal sextant angles by determining the arc radius using a chart plotting board, radar plotting sheet, or the simple formula (0.5 mark A to mark B)/ sin(horizontal sextant angle) = radius. Once the radius is known then a chart plot is performed by arcing the radius off navigation marks A & B then plot the arc of position from the radius point intersection to determine an estimated position. The chart plotting board image above shows a radius solution for a horizontal sextant angle of 45° and a distance between marks A and B of 16.6 nautical miles.

Sunday, November 21, 2010

Unique Short Table Sight Reduction

Combine Pub. 208 Dreisonstok with a modified 2102-D star finder for quick determining of the Sun's azimuth and intercept. Use the star finder to first derive azimuth which is then preplotted through the assumed position. Follow up with a calculated altitude using Pub. 208 Dreisonstok to get the intercept.

Tuesday, October 5, 2010

Set the 2102-D Star Finder without a Nautical Almanac

Set the 2102-D star finder without using a Nautical Almanac by scaling a radar plotting sheet as depicted by the above image.

1. Set Aries zero to month and day (clockwise)
2. Set blue latitude template to zone time of twilight (counter clockwise)
3. Select stars for twilight viewing.

The image example is for 12 October 2010 zone time civil twilight 1800 at 35°N 120°W

Try penciling in the Sun onto the 2102-D base disc using the slotted red template.

1. Set Aries to month and day.
2. Set red template to time of meridional passage.
3. Mark Sun's declination through the slot onto the base disc.

The twilight sky can now be set by rotating the blue latitude template so the Sun is 5° to 10° below zero altitude. For the southern hemisphere reverse the zone time direction to clockwise.

Wednesday, September 22, 2010

The Mechanical Watch

Image by Greg Rudzinski

There are many places where watch batteries are not readily available which makes the mechanical watch an important backup to the very accurate quartz watch. I recommend the Seiko 7s26 automatic mechanical movement which is affordable, simple , sturdy, and reliable. The best part about the 7s26 movements is that they can be easily regulated to better than ± 5 seconds per day.

Go to the link below for an excellent description on how to regulate a modern mechanical watch movement:

Thursday, August 26, 2010

Voyaging Tip #26: Icebox Space Management

Nest a 5 gallon, 3 gallon, and 2 gallon bucket into the icebox putting ice and beverages in the bottom 5 gallon bucket, frozen goods in the middle 3 gallon bucket, and dairy in the top 2 gallon bucket. This system will save space, conserve ice, and assist with icebox access.

Wednesday, June 23, 2010

The Celtic Button Knot

Image by Greg Rudzinski

The Celtic button knot is an alternative to the figure eight knot when a little more girth is needed to prevent pull through.

Friday, June 11, 2010

Genoa Wrap

Wrap an extra halyard around the vessels roller furled genoa for extra security against high winds. This is cheap insurance against sail damage when away from the boat for an extended period of time.

Wednesday, May 5, 2010

Voyaging Tip #25 : Fire Extinuisher Inspection

At the beginning of each sailing season inspect each fire extinguisher on board to verify that the charge indicator is showing full in the green. Additionally for a dry chemical extinguisher gently tap at the base of the extinguisher using a rubber mallet followed by a vigorous shaking of the extinguisher. This will loosen all the packed dry chemical to insure effective discharge.

Sunday, March 21, 2010

Voyaging Tip #24 : Camera Inspections

Inspect voids, tank internals, bilges, or any hard to access space using a small point and shoot camera equipped with a flash as a blind man's eye. The attached photo is of a diesel engine underside which is normally not visible to the engineer.

Monday, February 22, 2010

World Wide Ship Traffic

Very useful information regarding commercial shipping traffic is available at:

Click on a ship location for real time course, speed, destination, name, call sign, registration, size, photo, etc. This gives mariners a powerful tool to improve safety at sea.

Saturday, January 2, 2010

NC-77 Update

Bring back the Tamaya NC-77 almanac from a Y2K death ( as of 4/24/2017 ) is now  best done by subtracting 1900 from the current year as explained in a helpful comment listed below. The Geoffrey Kolbe LONG TERM ALMANAC 2000-2050 is still needed to up-date SHA and declination for the navigational stars.