NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2010 Sep 30, 08:45 -0700
While coastal cruising aboard a friends 42 ft. sloop yesterday a compass check was performed first by taking a hand bearing compass reading to a known distant landmark then compared this to the GPS position of the sloop to the same landmark. This confirmed that my hand held compass had zero deviation and could be compared to the steering compass for a check. While performing this compass check a reflection of the Sun was noticed on the steering compass globe. Out came the SLR digital camera to photograph a timed azimuth of the Sun reflected off the compass card center post as an experimental trial. Deviation worked out to about 1° east. The Sun was at my back so 180° is subtracted from the photos compass reading.
9/29/2010 GPS 34° 7.2' N 119° 25.3' W 18:25:19 UT Sun azimuth 148.3° true (palm program)
Variation 13° E Compass reading 314°
314° - 180° + 13° = 147° true observed compass azimuth
148.3° - 147° = 1.3° E deviation (or 1.3° low)
Greg Rudzinski
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