Astronomical Magnitudes

Why Can We See the Moon and Planets in Daylight?

By: Mike Luciuk

Several different types of “magnitude” are used in astronomy. Most commonly, apparent magnitudes are used to describe the brightness of stellar and solar system objects while absolute magnitudes are required to assess intrinsic brightness. A method is described to evaluate extended object versus sky brightness to calculate contrast, which explains why we can see Venus in daylight sky. There are specific procedures for calculating absolute magnitudes of asteroids, comets, and meteors. Factors such as color, albedo, and phase angles must, at times, be considered in their evaluation. The article will cover this topic with example calculations that can provide a firmer understanding of astronomical magnitudes.

Sperry Observatory is open for observing from 7:30 pm - 10:30 pm every Friday night with the exception of the 1st Friday of each month from September to May. A presentation on an astronomy related topic is given at 8:30 pm. This is free and open to the public.