<HTML>Bent wrote:
> The Cambridge Encyclopedia of Astronomy gives
> Sirius' proper motion as 1.324 arc sec. per yr.
Yes, that is the total proper motion, but (assuming that I understood him correctly) Dave was referring to the proper motion component in declination. I certainly was (with reference to the J2000.0 direction in dec). To this you must also account for the precessional change in the RA/Dec grid -- this fully accounts for the change in difference in dec between Sirius and Saiph that Dave has presented.
> This amounts
> to 4.59 * for the period in question, meaning that even if
> the proper motion of Sirius was at a right angle to the
> horizon, it would still be below the horizon in 10450 B.C.,
It is only the declination that is relevant to whether a star rises above the horizon. In -10450 Sirius had a dec of just over 58 deg, and so would have risen at any latitude south of 32 deg.
Also, are you aware that the declination component of its proper motion is southward (hence the '-' in -1.223 arcsec/yr)?</HTML>
