A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2021 Jan 3, 11:16 -0800
Robin, you wrote:
"I wondered whether your question about β Hydri was a jolly new year jest. Its Hipparcos Catalog number is 2021!"
That's awesome. I even thought your comment itself might be in jest, so I double-checked! I blame Eta Carinae for all of this. I suspect it is a coincidence magnet. Zeta rays or something...
"the proper motion given in Stellarium of 2648 mas/year is quite a bit larger than the value of 2244 mas/year that you get from the Hipparcos Catalog https://hipparcos-tools.cosmos.esa.int/cgi-bin/HIPcatalogueSearch.pl?hipId=2021 Maybe they are using an outdated source."
Yeah, the p.m. in Dec for beta Hydri as listed in Stellarium seems to be wrong by nearly a factor of two, which is huge. And the Bright Star Catalog from 1991 lists nearly the same p.m. values as modern catalogs, so I can't see how the problem could be an outdated source. It's all rather strange. I haven't spotted a pattern yet. I also noticed today that some of the proper motions for the bright stars of Cassiopeia seem significantly wrong (but Polaris is reasonable so it's not Declination-dependent).