Since ancient times the planets have been significant to all cultures. To the eye, they appear little different from stars. But a few days of observation makes it clear that they are different: they move in their own paths across the sky, changing with respect to the apparently fixed background stars. The word "planet" comes to us from the Greek word for "wanderer" (πλανῆται). Originally, the term included the five naked eye planets as well as the Sun and Moon, but not Earth. In modern times, the definition has shifted. There remains no widespread consensus on the matter. For my purposes here, I will consider a planet to be any body orbiting the Sun which is large enough to detect telescopically, so that also includes asteroids.

In addition to high magnification telescopic images of planets (which is tricky from Colorado, which sits under the jetstream and has skies which are not ideal for high resolution imaging), the planets can produce beautiful shows in the sky when they are near other planets (conjunctions). Mercury and Venus can also pass between the Earth and the Sun, called a transit.