Jupiter in July

[RikerChick 5]

 

Jupiter rises in the southeast and dominates the evening. The brilliant orb, shining at magnitude -2.7, never reaches great altitude, so the best views occur an hour on either side of midnight, when Jupiter crosses the meridian. The planet lies at the eastern end of Sagittarius the Archer as the month opens. A retrograde path carries it westward during July to a point just south of magnitude 3 Omicron Sagittarii.

 

Jupiter's disk is full of detail - some of it plainly obvious, like the dark equatorial belts. Spanning 47", Jupiter is so large observers can see features through telescopes of any size.

 

For many decades, the tool of choice for recording observations of the great planet was a sketch pad and pencil. Actually seeing Jupiter's cloud detail is a huge treat, but the fine eddies and spots appear only during brief moments of steadiness in Earth's atmosphere.

 

It's fair to say most casual observers never see this detail. Often, the planet's disk looks a bit like Jell-O. As turbulent air distorts Jupiter's light, the planet's disk seems to wobble and shake. Viewing with high magnification enhances this effect, so if you can't see much on Jupiter's disk, try using less power.

 

A webcam or video camera attached to your scope can capture rare steady moments forever. Image-processing software removes rapidly varying detail caused by chaotic turbulence and retains the persistent features on Jupiter's disk. What a great way to spend those cloudy nights!

 

As Jupiter's moons orbit, they appear to yo-yo east and west of the planet from our perspective. Io, the planet's closest major moon, makes the smallest excursions; it orbits in a couple of days. Europa's swing takes longer, and carries it farther from the planet. Ganymede and Callisto are slower still, taking 8 and 14 days, respectively, per orbit.

 

Occasionally, due to the particular line of sight, the moons appear close together or gather in unique arrangements. One such alignment occurs in the early morning of July 2. Callisto, Io, and Europa (from north to south) stand in a near-perfect line east of Jupiter around 4 A.M. Eastern Daylight Time (EDT). The trio spans an angle of 20", smaller than Jupiter's disk. Observers west of the Mississippi will best see this arrangement. Jupiter is near the horizon and dawn will be in progress for eastern observers.

[Wishfire 2]

I wish I had a telescope.