[yakiv]

Does anyone here know why the Einstein cross has 4 of the repeated image instead of being a continuous repetition around the lens object? It seems to me like you should see the magnified image as a sort of circle instead of having a finite number of repetitions.

Is this related to the lines forming a cross you see in pictures of stars?

[privong]

The lines forming a cross in pictures of stars is a separate phenomenon. That is due to diffraction from the support structures of the secondary mirror.

For a detailed answer to why the Einstein cross has 4 images, see: http://physics.stackexchange.com/questions/14056/how-does-gr...