"Diffractive Optics" technology

I am wondering why we don't see any of the "diffractive optics" technology in telescope lenses. I was intrigued by reading about the Canon camera lenses using this "DO" technology, which apparently allows more compact, lighter lenses. Check this out:

http://www.canon.com/technology/canon_tech/explanation/do_lens.html

Does anyone have any insight on this?

Camera optics and telescope optics are two different worlds that have different priorities. Excellent color correction can be obtained in a telescope lens with only two elements. You cannot make a camera zoom lens that way - it will require many elements in order to perform the zoom function as well as keeping the overall length short with repsect to the focal length (in other words a 500mm FL camera lens tends to be 250mm long by using many elements with built-in barlows).

A telescope tends to be physically as long as the focal length of the lens, something that is not tolerated in camera lenses. Therefore a telescope lens (or mirror) can be extremely simple. This simplicity has another overwhelming advantage over a camera lens - it allows full resolution of the aperture, something that you will not find in any camera lens, even the most expensive high end job.

Diffractive optics have other drawbacks that make them very poor candidates for high resolution high contrast telescope applications.

Rolando