Earth-Based Views of Mercury

Mercury, the planet closest to the Sun, is very difficult to observe from Earth. The planet is only one-third the diameter of the Earth, and can be studied by telescope only during the day or when the Sun is rising or setting. When Mercury is near the horizon, the interference created by Earth's atmosphere reduces the visibility even with the best telescopes.

	Earth-based telescopic photo of Mercury taken from Catalina Observatory 1.5 meter (61 inch) telescope. 72k GIF - 27k JPEG
	Map of Mercury prepared by E.M. Antoniadi in the 1920's. 173k GIF - 120k JPEG