Jupiter and WCIS in the Limelight

Jupiter, Callisto and the Wesley Comet Impact Scar
Sketch and Details by Jeremy Perez

Jupiter put on a great show tonight!

The impact feature is still hanging on and was readily visible through my 8 inch Dob at 120X and 240X. The best part was the addition of a beautiful shadow transit with Callisto hanging just outside Jupiter’s following limb. It also provided a nice contrast for comparison of the two spots. Callisto’s shadow was strikingly black, while the impact scar appeared more as a soft feature that seemed to take on the brownish color of the surrounding clouds. I spent more time getting a feel for the impact site itself, and did detect a horizontal elongation and slightly condensed appearance.

I had a couple moments of incredibly good seeing that showed up a lighter patch north of the impact scar and corresponded well to the position of a white spot in the area. I did not detect this as a hard oval, just as a subtle brightening in the area. Midway through my observation, high clouds moved in and foiled my attempts to finish up detail on the preceding edge before it rotated out of view, so the equatorial belts are a little plain in that part of the sketch. I finished the observation just as Callisto was dipping into Jupiter’s profile. What a great view!

Subject Jupiter, Callisto, Impact Scar and Shadow Transit
Classification Planet
Position* Capricornus [RA: 21:49:16.7 / Dec: -14:15:27]
Size* 48 arcseconds (Equatorial diameter)
Brightness* -2.8
Date/Time JUL 23, 2009, 2:00 – 3:30 AM
(JUL 23, 2009, 09:00 – 10:30 UT)
Observing Loc. Flagstaff, Arizona, USA – Home
Instrument Orion SkyQuest XT8 Dobsonian (203 mm dia./1200 mm F/L)
Eyepieces/Mag. Pentax XW10 + 2X Barlow (240X)
Conditions Mostly clear, occasional high clouds, humid
Seeing Ant. II-III
Transparency Mag 5.8 NELM
*Sources Starry Night Pro Plus 5.8.2