 The brightness may drop twice during the orbit, once when the secondary passes in front of the primary and once when the primary passes in front of the secondary.The deeper of the two eclipses is called the primary regardless of which star is being occulted, and if a shallow second eclipse also occurs it is called the secondary eclipse.The size of the brightness drops depends on the relative brightness of the two stars, the proportion of the occulted star that is hidden, and the surface brightness (i.e.