A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Peter Hakel
Date: 2021 Nov 26, 13:51 -0800
To your question: "what specific values are you using for the proper motion in RA/SHA and Dec for Rigil Kentaurus (alpha Centauri)?"
I am using:
mu_Rasc = -3.608” per year
mu_Dec = +0.686” per year
and the proper motion is modeled to be linear, just like for all the other stars. I revisited one of my sources for this data:
The image you posted from A&A is indeed quite complicated. I suppose, however, that as long as the center of mass of the system appears to move linearly enough, the individual components don’t seem to deviate too much from that to degrade the result for celnav applications. I’d figure that the center-of-light position (which would weigh the brighter “A” component more than “B”) would be the most appropriate one for observations with a sextant.