Astronomy for Beginners
Here’s where you’ll find observing guides, how-to articles and great astronomy hints and tips. Don’t forget to also check out our comprehensive astronomy dictionary.
A measurement of the optical power of lenses and curved mirrors in telescopes and binoculars. The dioptre is the reciprocal of the lens or mirror’s focal length in metres.
These are craters who have been infilled, buried or submerged by geological processes but are sometimes still just visible on the surface of a planet or moon.
This is a measure of how reflective a surface is – the ratio of the amount of electromagnetic radiation (like visible light and infrared) reflected by a surface, to the amount that falls on it.