Ratio aspect between Jupiter and its moons

[cimo80]

Looking at the attached picture that show Jupiter and its four biggest moons, it seems the Io, Europa, Ganymede and Callisto have a ratio dimensions about 1:10 with Jupiter.
But Jupiter have a diameter of 140000 km and its moons an average of 4000 km so the real ratio is 1:35.
Why does it happen this illusion?
Thanks.

Simone

 

[billslugg]

Everything has a certain amount of blur around the edges due to the atmosphere , optical imperfections, dirt and reflections on the lenses. It doesn't much affect the size of a large target such as Jupiter but it can dominate a small target such as the moons making them appear much larger than reality.