NavList:

Greg wrote:  Vessels out of sight of land still need to check the gyro and magnetic compass with celestial observations. Compass checks using a Sun or star azimuth remains an important part of the days work for both commercial vessels and yachts.

Greg.  One of the good things about a periscopic sextant mount is that every celestial shot is also a compass check.  How do they manage a compass check on ships.  Do they have a similar device, or do they wait until sunrise or sunset and use amplitude tables.  I suppose you could measure the bearing of a rising or setting body with a peloris, or failing that, point the vessel at the sunrise or suset and take the compass reading.  While I'm at it.  Please will someone tell me if I've got the labels correct on the slide below on how William Bligh might have done a compass check.  As Frank pointed out recently, I'm having great difficulty thinking upside down at the moment.  Dave