x-ray rafter finder?

Hello, I heard someone talking about a really good stud/rafter
finder. It is like an x-ray of the roofs underside. I think they said it was made by Bosch and cost around a thousand dollars. I can not find it on the internet.
I am installing solar panal racks on a house which has regular apshalt shingles. The average stud finder obviously will not work very well. I am aware of tapping a hammer around and finding the hollow spots, but this still seems too uncertain.
I also can not get to the rafters from the attic either.
Does anyone know of this product or another which will
find the rafters?
thank you,
kevin

 

A thousand bucks?

I'd rather go low tech and drive in a long screw with shorth threads to see if the threads were biting into wood or if the screw spins freely after being driven past the sheathing - 50¢ and maybe a tube of roofing cement

 

Why not use a longer thin bit (like 1/8")...you'll know when it comes outr in the attic or hits a rafter. Just mark the bit with tape or paint at the 1 1/2" mark or so...if you still get resistance...yer in solid wood.

Have you measured from the end of the roof? Depending on the age and construction you should be able to find them within 1/2" or so using a tape measure and accounting for trim.

 

First check the soffit tails, second, the gutter spikes. Third, the 6' straight-edge across the roof while standing near to watch the deflection.Shift your weight back and forth. Fourth, I'm off work now, fly...........

Be safe, Gary