Y! has an interesting article in which a space.com astromoner explains how to detect planets by their phases (like phases from the moon). Its called the 'fade-in fade-out' technique. Calculations are in the article, but its been "dummed down" into laymans terms. Still an interesting read.
"An entire fraternity of strapping Wall-Street-bound youth. Hell - this
is going to be a blood bath!"
-- Post Bros. Comics