The full moon and the planet Jupiter, as viewed from the front of my house earlier tonight, in a clear sky over Galway. Jupiter’s moons are not visible in the top picture (even a blown-up version). The bottom picture shows Jupiter in the evening sky on a summer night in 2007, with the moons Europa, Io, Ganymede and Callisto clearly visible.
Both images were taken with the same lens , but attached to different cameras. In both cases, the lens was a Canon 100-400mm zoom (zoomed out to 400mm). The picture this evening was taken with a Canon 7D, whereas the picture taken in 2007 was taken with a Canon 5D Mark I. In both cases, the magnification was about 8 times normal (i.e. what the human eye can see). By contrast, Galileo’s telescope, with which he used to discover the Jovian moons nearly 403 years ago, had a magnification of about about 20 times normal.