NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: The development of bubble sextants
From: Paul Hirose
Date: 2009 Aug 17, 15:45 -0700
From: Paul Hirose
Date: 2009 Aug 17, 15:45 -0700
douglas.denny@btopenworld.com wrote: > This particular situation in discussion, however, of a sextant bubble held by a person standing on the Earth, is an object tied to the Earth and the "Coriolis" force here (i.e. the horizontal force due to rotation of the Earth) will be real. My example of the North seeking gyro is more apt for it is the (real) force which makes the North-seeking gyro work. It was this which I was thinking about. Sorry for the loose interpretation of Coriolis if it caused confusion with the aircraft and bullets cases. Coriolis force doesn't affect a bubble level when it's stationary with respect to the ground. If it did, the eastward velocity due to Earth's rotation would force us to apply a Coriolis correction to convert a star's geocentric right ascension and declination to altitude and azimuth for a stationary observer. Of course no such correction is necessary, even in precise work. Coriolis force doesn't make gyrotheodolites seek the meridian either. In fact, these devices work best at the equator (where Coriolis is zero) and become useless near the poles. -- --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---