Stellar Proper motions are not right
I noticed in Stellarium 14.1beta (and back to Version 12) there is a problem with the proper motions.
If you look at Alpha Centauri, the future motion is moving northwards at a PA of about 345 degrees, however that is not possible. If the HIP2 parallax is -3679.25 and +473.67 mas/year, the position angle should be about 277.3 degrees, calculated as tan-1(-
Yet if you select the star HIP 57367 (11.5 magnitude) in Musca, which has an equally large proper motion but is in the opposite direction. I.e. +2663.91 and -347.38 mas/ yr, the position angle is +97.4 degrees.
The motion in Stellarium is seemingly wrong for Alpha Centauri but appears roughly correct for HIP 57367.
I also checked , being roughly correct.
Arcturus, pm. -1093.99, -2000.16 mas/yr, moving in PA 208.7 deg.
Sirius , pm. -546.01, -1223.07, PA 204.8 deg.
Barnard's Star -798.71, 10337.2 mas/yr, PA 353.6 deg.
1) Please check the calculations when adding proper motions.
2) Could someone point out the C++ file that does these proper motions calculation?
3) Are the proper motion calculated independently of the precession, as some stars move as arcs against the background stars in Stellarium rather than straight lines? (I.e. Follow the motion of HIP 57367.)
Alpha Centauri is a critical star because of its brightness and being the closest star, and educationally is important to many who us Stellarium. It is critical that something is done to fix these apparent errors.
Kind regards and appreciation to its solution,
And hope this is useful.
I use Mac OS X 10.7.5, ATI Radeon HD 4670 256MB graphics
Note 1 : it is possible there is something wrong in solving the tan ambiguity here, where the PA is being calculated incorrectly.
Note 2 : As previously noted, SIMBAD gives the following proper motions;
Alpha Centauri : -3608, 686 mas/yr [PA 280.8 deg]
Alpha Centauri A : -3679.85, 473.67 mas/yr [PA 277.3 deg]
Alpha Centauri B : -3614.39, 802.98 mas/yr [PA 282.5 deg]
As the stars are labelled individually, the two components appear to diverge and are moving wider apart, rather than towards their common mutual shared motion.
The HIP2 file should be modified to either Alpha Centauri's mean motion of -3608, 686 mas/yr [PA 280.8 deg], or the mean motion of AB -3648.62, 638.33 mas.yr (HIP2) [PA 279.9 deg]. This number should be assigned to both the A and B stars in Stellarium's HIP2 star file.
|Changed in stellarium:|
|status:||New → Confirmed|
|importance:||Undecided → High|