One of the more challenging subjects to capture with a camera is the night sky. Planning is very helpful. Knowing where you want to be, what phase the moon will be in, when it rises, and other factors change the photography drastically. But then, some of my favorite night sky shots have spontaneous elements to them as well, such as a car driving by. This is also an area where I can see the progression of my skills, so it's fun to revisit.
