This is for Mikecr and anyone else that might be interested.
This is a trick that many top long range Benchrest shooters use. Some people don't like it, but if you get used to it and learn to trust it you won't need to worry about mirage anymore.
BulzEyePro All-Competition Optical Boosters with Universal Housing
I have one and have learned to trust it and love it. If you decide to try one you will need to call on the phone first. Most likely no one will answer, but leave a message. The guy will call you back in a short time. I think he does this because he needs to explain how to make your measurements so it will work correctly for you.
PS: The coatings were developed for satellite cameras and are good for beyond 3,000 miles incase someone wants to get into some REALLY LONG RANGE stuff.