Jupiter is a big planet and it is located relatively near to us so as to be easily observed through a telescope. At opposition it almost measures 50 arcseconds. Callisto is one of its four Galilean moons. It is really small apparently, 1.6 arcseconds exactly in the picture above.
Even though it is really small to be explored through an earth-based telescope, Antonello Medugno has been able to extract some albedo features. He used its 14 inch Meade LX200 and an effective focal length of almost 9 meters. Figure out a refractor tube of 9 meters long ...
