NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Will anyone ever find Shackleton's lost ship?
From: Peter Monta
Date: 2022 Feb 11, 12:31 +0000
From: Peter Monta
Date: 2022 Feb 11, 12:31 +0000
Hi Robin,
I can't claim to be an expert but I think it unlikely that the proper motion of isolated stars changes enough over the course of 100 years that it would make a significant difference for us.
I'm not an expert either, just a hobbyist in astronomical image processing. Sure, most proper motions would change very little in 100 years, but I was angling toward the issue of uncertainty growing over time, not a true change in the underlying proper motion. If proper motion has uncertainty x mas/year, then over 100 years the uncertainty grows to 100*x mas.
If a quick check of the catalogs has not let me astray, x for Hipparcos is about 1 mas/year and for Gaia about 0.18 mas/year, over 5 times better. So Hipparcos positions 100 years ago will be out by 100 mas. This is still pretty small, only 0.2 second in lunar occultation timing.
Cheers,
Peter
