Last Sunday night (the 25th) I tried to view the globular cluster NGC 6235 in Ophiuchus from Lake Sonoma (about 80 miles north of San Francisco) with my 24-inch f/3.7. Normally, this would be a piece of cake. The problem was Jupiter was parked practically on top of the not-so-bright globular, completely obliterating it from view. That night the separation between the center of the globular and Jupiter was just 3.5’ and the glare from the planet (mag -2.2) washed out the 10th magnitude globular. I suspected some graininess that was probably the core of the globular, but nothing else. Coincidentally, Ganymede was in the process of being occulted, so as a consolation prize I watched the satellite brush up against Jupiter and disappear.
The past few days Jupiter has been marching east about 3’ per day and on Thursday night it was sitting 8.8’ east of NGC 6235. I thought I'd give it another try from Lake Sonoma. As a bonus, Callisto, was superimposed on the south portion of the halo of the globular! Using 260x (10mm Zeiss Abbe), it was easy to keep Jupiter well off the edge of the field and Callisto was nicely resolved as an obvious 1.3” disk. Less than 2’ north of Callisto (1.8’ to be exact) I immediately noticed the central portion of the globular as a small hazy patch, directly on a line with Callisto and a mag 11.5 star just north of the cluster (technically in the cluster's outer halo). The glow was too faint to resolve, as Jupiter still brightened the field, except for a single 14th magnitude cluster star that was just resolved.
Interestingly, Jupiter has been invading NGC 6235’s space for awhile. In fact, Jupiter and the globular cluster had a very close “conjunction” last new moon, when they were less than 5’ apart! I also tried to see the cluster at that point (July 28th) with limited success. In the past month Jupiter has actually been retrograding so that two weeks ago it was nearly a ½° west of NGC 6235. But then it started heading east in its usual orbital track and now has met up with NGC 6235 this new moon. But it’s steadily moving east, and the globular will soon be a relatively easy catch again.
The attached MegaStar chart (with DSS overlay) shows Jupiter last Sunday night (on the right), with Jupiter’s disk plotted each 24 hours. The last one (on the left) shows Jupiter’s position on Thursday night at 9:30 PDT.