At left is my first attempt at imaging Jupiter. My 120 mm telescope has a theoretical maximum resolving power of one arcsecond, while Jupiter appeared about 45 arcseconds across.
The image at right was captured on 21 September 2020. It shows Jupiter's Great Red Spot. The moon Io is visible just to the right of the planet and its shadow stands out sharply on the surface.
These images use “lucky imaging”: thousands of fast exposures are recorded over several minutes, analysed in software such as AutoStakkert and RegiStax, and the clearest frames are combined to improve visible detail.