Suppose a star lying on the celestial equator has a proper motion, directed along the equator, equal to the rather large value of Barnard's star, namely 10 arcsec/yr. How long would it take this star to change its right ascension by 1 hour?

Question

Quizplus · Accepted Answer

The celestial equator is 360 degrees, and 1 hour of right ascension corresponds to 15 degrees. With a proper motion of 10 arcsec/yr, it would take 5400 years to change by 15 degrees (1 hour of right ascension), since 15 degrees equals 54000 arcseconds.

Suppose a Star Lying on the Celestial Equator Has a Proper