The trickiest part of measure 6 of the Moonlight is remembering the b sharp octave that the left hand plays.
Because the first movement of the Moonlight Sonata is slow, many aspiring pianists think it is easy and are surprised and discouraged because it isn't easy enough.
Sometimes what makes it hard is a gap in knowledge. In this case the gap is easily closed.
This piece uses all 7 white keys and all 5 black keys. In order to understand the notes, understanding what sharps are, and that they can be white keys as well as black ones is critical.
I created a free mini course, Know the Keys of the Piano by Name (click here to get it) to make sure that students know all of the names of the keys of the piano. It is how I start all of my students.