Binary Star

Visual binaries are those stellar systems which appear as two stars in the eyepiece of a telescope. They are traditionally observed by manually measuring, at the eyepiece of a telescope, the angular separation of the two components. The angle the fainter stars make with respect to the brighter component is also taken into account, and refers to the north direction on the plane of the sky. If the measurements of each component are made and photographically compared to background stars, the masses of each star can be found. Many observations are needed over a period of time commensurate to the period of revolution of the pair.