Sky & Telescope is making four illustrations, two photographs, and one animation available to editors and producers. Permission is granted for one-time, nonexclusive use in print and broadcast media, as long as appropriate credits (as noted in each caption) are included. Web publication must include a link to SkyandTelescope.com.

A lunar eclipse occurs when the Moon passes through the shadow cast by the sunlit Earth. Like any shadow, it has two components: the outer, lighter penumbra and the inner, much darker umbra. When the Moon enters the penumbra, where just part of the Sun's light is blocked, it becomes only slightly dimmer. Only when it passes into the umbra does it look markedly different. But even when completely within the umbra, the Moon does not disappear altogether. Sunlight skims through the Earth's atmosphere and is refracted (bent) into the shadow, casting a reddish tinge upon the lunar surface. The diagram is not to scale. Click on the image to download a publication-quality JPEG (399 kilobytes) by FTP; the illustration is also available without labels (344 kilobytes).

Sky & Telescope illustration by Gregg Dinderman.

Sky Publishing Corp. was founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, the original editors of Sky & Telescope magazine. The company's headquarters are in Cambridge, Massachusetts, near the Harvard-Smithsonian Center for Astrophysics. In addition to Sky & Telescope and SkyandTelescope.com, the company publishes Night Sky magazine (a bimonthly for beginners with a Web site at NightSkyMag.com), two annuals (Beautiful Universe and SkyWatch), as well as books, star atlases, posters, prints, globes, and other fine astronomy products.