GREEN COMET MAKES CLOSEST APPROACH TO EARTH: On Sept. 10th, Comet 21P/Giacobini-Zinner makes its closest approach to Earth in 72 years. The small but active comet is going to be easy to see in small telescopes and binoculars as it glides through the stars of the constellation Auriga about 58 million km from our planet. In the week ahead, it will also pass right in front of a rich star cluster, providing a spectacular photo-op for amateur astronomers. Visit today's edition of Spaceweather.com for details and observing tips.

The close approach coincides with a New Moon, providing a velvety-dark backdrop for the passage of the comet. The best time to look is during the dark hours before sunrise when the constellation Auriga is high in the eastern sky. If you have a GOTO telescope, use these orbital elements to point your optics. Detailed sky maps can help, too.

Shining just below the limit of naked-eye visibility, the comet will remain easy to photograph for the rest of September. If you can only mark one date on your calendar, however, make it Sept. 15th. On that night, 21P will cross directly through the middle of the star cluster M35 in the constellation Gemini. Astronomer Bob King writing for Sky and Telescope notes that "the binocular view should be unique with the rich cluster appearing to sprout a tail!"