Crescent Venus

I rented a 400mm lens with a 2x extender to see what it could do.  This is what Venus looked like.

I was a bit surprised that the image wasn't sharper.  That may have been my fault.  With the 2x extender, I was forced to manually focus and Venus was small enough to be difficult to tell whether the focus was right.

Nonetheless, the crescent shape of Venus is clear.  This was one of the primary pieces of evidence that led to the downfall of an Earth-centered Universe.  Mercury has phases too, but it's really difficult to image, making Venus one providing the convincing evidence.