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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: CP-300/U Star Finder
From: Paul Hirose
Date: 2015 Mar 10, 22:09 -0700
From: Paul Hirose
Date: 2015 Mar 10, 22:09 -0700
On 2015-03-09 10:01, Russ Keller wrote: > Are these limited to a particular span of years. Or in other words are these still useful for sight planning? Yes, they still work. The precession of the celestial equator causes a constant movement of the SHA/dec coordinate system. However, this amounts to only one degree (in great circle measure) every 72 years for a star on the ecliptic, less elsewhere. Even if the coordinate system maintains a fixed orientation, the space motion of the stars with respect to our solar system gives them slowly changing coordinates. That's called "proper motion". At 3.7 arc seconds per year, Rigil Kentaurus has the greatest proper motion of the navigational stars. But that's almost 1000 years per degree, so the effect on a star finder is negligible compared to precession.
