I had a friend that was down in his basement watching tv during a Thunderstorm. He stated that when the Lightning struck their house. He said that you could see it the electricity flow around the Copper that had been placed between the bottom plate and Concrete foundation.Thing is the dish is not being installed up high, it's going on a wall inside a atrium and will poke up above the lower edge of that roof about a foot. It might be best to not ground at all. I've seen hundreds of dishes over the years with no ground. My only worry is static build up from wind frying a LNB or receiver.
He said that it looked like a Jacob's Ladder http://en.wikipedia.org/wiki/Jackob's_ladder_(engineering)#Visual_entertainment He said that they ended up losing some things like some phones, an answering machine, the microwave, but no tv's, due to they were all grounded to the electrical ground, along with the TV antenna on the mast next to the house.