NOTE Aug 24: I posted a followup to this article with two more videos.
This may be a very common event after all: another optical flash has been observed on Jupiter, again from an observer far east of the Greenwich meridian, though it was not Anthony Wesley (for once). This time it was Japanese amateur astronomer Masayuki Tachikawa who was pointing a video camera-equipped telescope at Jupiter and who was fortunate to capture an optical flash as it happened. Here's the video:
Optical flash on Jupiter captured by Masayuki Tachikawa, Japan Optical flash on Jupiter captured at 18h22m12s (+/- 1 minute) on August 20 (UT). The video was taken by an amateur astronomer, Mr. Masayuki Tachikawa in Kumamoto city, using a Philips Toucam Pro2 attached to the telescope, Takahashi TAO-150 f1100mm with teleview power mate X5. Further information here and here. Masayuki Tachikawa
And here's a still:
The still and video came from this page on the website of the Association of Lunar and Planetary Observers of Japan. If I understand the text on that page correctly, a few other Japanese observers attempted followup observations (mostly one or two planetary rotations later) and observed no trace.
Compare these images to the ones from the June 3 event:
June 3, August 20, that's a rate of roughly four of these per year -- keep watching, amateur astronomers, and keep those video cameras running! You may catch the next one. This actually is a perfect example of why amateur astronomers remain relevant and important in astronomy: no professional telescope is going to be hanging around shooting video of Jupiter night after night, but you don't need an enormous professional telescope to discover the latest Jupiter impact, or to watch the changes and motions in its belts and storms. Time is more important than size, and time is what amateurs have that professionals don't.