NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Compass Deviation from CelNav
From: John Brown
Date: 2014 Oct 24, 03:05 -0700
From: John Brown
Date: 2014 Oct 24, 03:05 -0700
Hi Jonathan
It is standard practice at sea in large vessels to measure the bearings of any available celestial body, well above the horizon, using an azimuth circle, or alidade which is equipped with a reflecting prism and the necessary shades for sun observations. An accuracy to half a degree is the best that can probably be obained. For the sun, the shadow cast by a sighting vane might also be used.
As these options are not normally available in a yacht, compass error can be determined from observing the sun, using a shadow pin if fitted to a horizontally mounted compass, or with a pelorus or sun/astro compass. I would be very pleased to achieve a one degree accuracy in a yacht using any of these methods.
Regards
John
