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• Unlike the last quarter moon, Jupiter's disk won't look half-lit through the telescope. From our vantage point in the inner solar system, far-off Jupiter always looks full from Earth. However, as viewed from our planet, the shadows of Jupiter and its four major moons - Io, Europa, Ganymede and Callisto - angle out at a maximum of 12 degrees westward from these worlds at west quadrature.
• That's why, at and near west quadrature, the shadows of Jupiter's moons cross Jupiter's disk a maximum amount of time before the moons themselves do. As the moons circle behind Jupiter, the moons sweep into Jupiter's long shadow a maximum time before they swing behind the giant planet itself.
• Nearly three months from now, on December 3, 2012, Jupiter will be at opposition - 180o - from the sun in our sky. At and near opposition, Jupiter's moons and their respective shadows cross Jupiter pretty much in concert.
• Awesome image of two bright planets - Venus (bottom left) and Jupiter (top, middle to right) - with constellation Orion at right. You can recognize Orion's Belt as three medium-bright stars in a short, straight row. Photo taken September 4, 2012 by EarthSky Facebook friend Susan Jensen in Odessa, Washington. Thank you, Susan! Click here to expand.
• If you're up at or before dawn on Friday, September 7, look for the waning gibbous moon, Jupiter at west quadrature and Venus in the eastern sky.