portableclassrooms.kubuildingtech.org

http://books.google.com/books?id=N7IBkE7Am_gC&pg=PA36&lpg=PA36&dq=skylight+orientation+south&source=web&ots=gAH-lipNpe&sig=RMgstQJWgYkU5cQlo0Gm2q1lCy0#PPA37,M1   This link gives formulas to calculate skylight openings and angles.  There are also general rules of thumb on skylights and clerestories.