I just did this a couple weeks ago at the potential new place. I was a few minutes off on the time I looked outside, but it looked pretty clear, so I think I am good. Which makes me happy. But some guy was having the same problem, so I thought I'd try to help and answered the thread.
TivoCommunity Thread on Tools to Check Dish Placement
I pointed the guy at:
http://perso.numericable.fr/~gjullien/satellite.htm
which is the site that actually does the calculations.
Hopefully it is helpful. I love that moon check thing. It is cool. I've used it a bunch of times. :-)