NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2017 Oct 12, 08:21 -0700
Robert,
The Otis King model K (ser # T3127) that I'm using for trial sight reductions has a measured circumference of 1.043 inches which works out to 65.53 inches of scale length for the 20 spirals. Practical sight reductions are quicker, smoother, and easier to read when compared to a Dietzgen 8 inch circular slide rule that I have. The worst discrepancy recorded so far after several dozen Hc sight reduction trials is 2.5 minutes of arc when compared to the Casio fx-260 results. Most Hc results were within 1 minute of arc. The scale between 7 and 10 only reads to about 3.5 places. Below 6 is very close to 4 place precision. I'm satisfied with the size, cost, and practical function of the OK. It give it an A for non-electronic small craft sight reduction.
Greg Rudzinski
From: Robert VanderPol II
Date: 2017 Oct 11, 21:04 -0700The smaller tube on my O-K is 0.758" diameter . That means circumference is 2.38" (0.758" x pi). Ignoring the effects of it actually being a helix, that gives a scale length of 47.6" (20 x 2.38") for the 20 cycles I counted on mine. I'd previously heard that the scale was equivalent to 42". Accuracy to 3 significant near 10 and 4 near 1.
My 8" Atlas circular with a 30 cycle sprial is 4 significant digits from end to end.
Bob II
