Stargazing: Observing Jupiter's motion

Stargazers shouldn't have any trouble finding Jupiter from now until spring. After reaching opposition on Dec. 2, our dazzling bright "evening star" can be found 35 degrees above the eastern horizon at 7 p.m.

Jupiter's highest altitude and its best time to be viewed through a telescope in steady air, however, are around 9 p.m. when it stands about 60 degrees above the southeastern horizon. One clenched fist held out to the horizon equals about 10 degrees.

Good binoculars or a small telescope will also show the planet's four large Galilean moons. They appear as bright "stars" on either side of Jupiter. From innermost to outermost, they are Io, Europa, Ganymede and Callisto. As each moon orbits around Jupiter, they will shift positions from night to night. It's impossible to identify the moons without looking at a reference chart, so our illustration today will show their position this weekend at 9 p.m. as seen through binoculars. Sky & Telescope and Astronomy magazines also print a complete chart each month.

-- By Dan Malerbo, Buhl Planetarium and Observatory