A handbook of double stars, with a catalogue of twelve hundred double stars and extensive lists of measures. With additional notes bringing the measures up to 1879 (1879)
by projection. Hence we find in succession a, i.e. the angle which the line of nodes makes with the axis of ;r, the meridian through the star ; i, the inclination, from the condition cos i = ||, Sa and Si being the major and minor axes of the harmonic ellipse : e = ^- J L S r- ) AC ' and ^ = — -^ =… … X "11 = sec i tan (\ - a), ^^^ ^^ and therefore X is known. To construct the ephemeris graphically, it is necessary to divide the ellipse into equal sectorial areas by radii drawn from the focus. This may be accomplished as follows : —
