Hand-holding a Droid smartphone over an eyepiece is not the best way in the world to get an astrophoto, but it sometimes works!

This is almost precisely at Second Contact (complete ingress phase) of the Venus Transit of 2012. Notice how the edge of the sun and the adjacent edge of Venus seem to reach out and "grab" each other? That's called the black drop effect.

Historically, this effect was taken as "proof" that Venus has a thick atmosphere, however it is now generally thought to be an optical illusion due to contrast and optical system limitations.

Here's a drawing as depicted by Torbern Bergman in 1761 (from Wikipedia):

<a href="http://en.wikipedia.org/wiki/File:Venus_Black_Drop_effect.png" rel="nofollow">en.wikipedia.org/wiki/File:Venus_Black_Drop_effect.png</a>