Range finding with a laser, help?

[Torchwood]

Ok, trying to add a laser for night range finding to my add on. Originally wanted to get a IR laser, but settled for a cheap £10 red laser from ebay to practice with, Tried it last night, and was a bit disappointed. Cheap laser was fine, in fact very good, throw was almost 400 yards ( not visible to the eye but visible on the screen). The problem was probably that it wasn't high enough. It was 10cm high ( from center of scope to the center of laser), how high should it be? I'm ordering a riser block, so need some help.
I was fairly ok on 12 mag. Is there a formula?

Cheers
Toni

[paulham]

If I recall correctly, for the laser to be worth it, it needs to be around 12 inches from the line of sight...

Haha

[Torchwood]

Lol, that's the end of that idea, I can't imagine my self walking around in the field with a stick 12" long on top of the scope.
I was fairly sure it would work around 4-5". But my 4" setup is not working for the purpose. Good job I only experiment with a cheap one.

[paulham]

I think it explains it on the chairgun program. Download it for your computer and have a look.
It plots the laser on a graph