Aiming angel solarpanel to sun?

[Guest]

I have bought a solarpanel of 50 Watt. Normally when the boat is moored the solarpanel will be flat on the coachroof so it can pamper the battery. When we are on board I want to aim (is that the right word?) it at the sun. Does anybody know on what angel the solarpanel must be set? I need this information for constructing the pole. I sail in Holland ean want to use the panel in the summermonths.

Thanks