Owl! Big Owl!

Last night the chickens started carrying on and the guineas were really telling it.  I look out my bedroom window and sitting on top of my brother in law's camper was a really big owl.  I think it may have been a great horned owl?  I wish I had grabbed my camera!  When my husband opened the back door to go out there it flew off and the wingspan was really big, maybe 4 feet or so. 

What can you do to scare off owls?  I know you can put owl decals up for certain things but what could be an owl decal?  It's obviously not afraid of the light because my silly chickens roost on a rabbit hutch under my big yard light and the guineas are right next to them roosing in a pine tree.  I don't think I can shoot it in the State of Ok and honestly I would hate to, I'm a bird lover and before I got my chickens I had an owl that lived in my yard and it would whooo whooo in the evenings and would get really close to you.  It would come sit in the tree in my front yard not 20 yards from me.  I hate to kill it but I don't want it to eat my chickens.  I probably could coop up my chickens but the guineas - impossible.

It's back!  Any suggestions?  I tried to take a picture but my camera takes horrible night pictures.  I know it has a white neck and is maybe a foot tall.  It really doesnt look all that big until it flies and then it looks huge.  When I go outside it flies away but eventually it will snatch a guinea or chicken.  :(

This is the best picture I could get and i had to lighten it up, mess with the contrast etc. to get it to even come out this good.

What is predator preventor?