We mentioned on 29 July that Jupiter is special this year. There are a couple of Mutual Phenomena between Galilean moons around August. Still, not all are observable in Hong Kong (e.g., Jupiter is below the horizon when the events happen). Some of them are not particularly interesting because only one or two phenomena happen within the same night. For example, the occultation and then the eclipse of Europa by Ganymede manifested in the small hours of 9 August (HKT, same below).

However you don't have to be disappointed! You may look forward to the serial phenomena of Jupiter's moons during 15-16 August. From around 7 pm (Jupiter rises) to 3 am, a series of moons' transit, eclipse, occultation and Mutual Phenomena happens that night. Multiple phenomena even co-occur sometimes!

To observe the above phenomena, you need an astronomical telescope of 20 cm aperture or more, with at least 200 times magnification, and a very stable atmosphere.

Online version of the "2021 Astronomical Events" special exhibition: https://hk.space.museum/zh_TW/web/spm/exhibition/specialexhibition/2021-astronomical-events.html#event3

Computer simulation (the positions of Jovian surface features such as the Giant Red Spot can differ from reality): https://www.youtube.com/watch?v=B3A3kbIkZh8