I found this to be rather an enjoyable read for a prestige class. I'm not sure if I'll be able to playtest this one but it looks good.

Just a quick question -- if you designate a spell as lunar or solar can you change your mind about it at a later date? I think once a spell has been designated, you shouldn't be able to change it to another designation or players will bypass the penalty. You may want to expressly state this to avoid that particular issue in the future.

Debby