Jupiter and moons by Dave E, on Flickr

I wasn't even aware I was shooting a planet at first. I was just trying to see if the manual focus assists worked on a star. The triangles, surprisingly did work, but the color tint did not.

Reviewing the image I thought the MF assist did a poor job at first... it was a bright blob (Auto ISO 25600), not the sharp point I was expecting. I did an AF shot to compare to, and also had a bright blob, but that's when I noticed there were moons. I was shooting a planet, not a star. I ran inside to grab the extender.

I applied an exposure drop over Jupiter so that both the planet and moons were visible at once. Seems that I lost Ganymede in this shot. A stop or two brighter and Ganymede is there, but I can't recover any detail on Jupiter.

Apparently you can get similarly sized shots of Saturn too. If anyone has an R7, the 800mm and a 2X extender, I figure you should be able to get about 5X the detail. (2*800/700) squared.