Venus ranks as the third-brightest object in the sky, outshone only by the Sun and the Moon. At times, the planet’s light can cast shadows.
From the earliest times, humans have been captivated by its brilliance. The oldest surviving document regarding the planet is the Venus tablet of Ammisaduqa, which was created before 1600 b.c. This cuneiform tablet records Venus’ appearances over two decades, giving the correct time intervals between them.
Observing Venus
Because it’s so bright and its appearances in the morning and evening skies last for months, Venus is easy to observe. During its orbit, the planet goes through a pattern of inferior conjunction (when it’s between Earth and the Sun), greatest western elongation (when it’s at its maximum distance from the Sun in the morning sky), superior conjunction (when it’s on the other side of the Sun from Earth), and greatest eastern elongation (when it’s at its maximum distance from the Sun in the evening sky).
One more event — greatest brilliancy — occurs approximately 36 days before and after inferior conjunction when the planet lies 39° from the Sun. The geometry of the Sun-Venus-Earth angle at these times makes Venus appear brightest from Earth.
The phases of Venus are of interest to observers, as is another easy-to-see aspect: size change. Mercury looks twice as big near inferior conjunction as it does at superior conjunction. Venus, on the other hand, is more than six times larger.
Daytime observations of Venus are not as difficult as most amateur astronomers imagine. In fact, it’s far better to observe Venus during the daytime, or at least in twilight, because the background sky brightness reduces the deleterious effects of the planet’s brilliance. And observing Venus in the daytime sky is easy: Simply point your telescope at Venus before daybreak and allow the drive to track it until after sunrise.