[Al Skierkiewicz]

Phil,
What you are describing is known as a Cassegrain Feed point. It is very common for some of the larger telescopes (Mt. Palomar I think is this type of feed) and for the Celestron line of compact reflector telescopes. The feedpoint (or collector) shape is a little more complex but if you are making a simple planar reflector (one in which the reflector is only a cross section of a full 360 degree parabola you might have an easier time. Many large satellite dishes use this type of feed and one of the design factors is during sun transit. This is when the sun passes behind the geosynchronous device twice each year. We can actually watch the reflection pass across the feedhorn window and it does raise the temperature of the feedhorn during the 15-30 minute transit.