I was assuming that your main interest was aligning your disk, and since the price of a commercial satellite finder won't even buy you the housing if you want to build it yourself I pointed to that solution. Of course, when you see it as a project it is a totally different story
Although taking a scope up to the roof is not something I'd recommend, it is totally possible to measure the dc from a RF detector with it.
But you will just be using it as a multimeter, not much pride in that...
Anyway, here's a schematic as a start, if you still feel that you want to use your scope you can always leave the meter out.