I'm sorry.
I just read the title to your question.
'Angle of Depression'
You did tell me what angle you were talking about - I just didn't see it, my eyes must have been closed!
that sketch that L1m3 attached was accurate.
I did see it open once but every other time it has refused to open.
Did you actually get to see the answer that L1m3 offered you?
Are you still interested at all or maybe you've got better things to do over your Christmas break.
Anyway, if you are still interested and you can't read L1m3's answer please post again.
Melody.