Quote:
Originally Posted by skysurfer
Telephoto lenses such as the Canon 300/2.8L, 400/2.8L and 600/4L have more than ten elements and then it is possible to make color-free images with such a short focal length.
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Apples and oranges. Telephoto lenses have to perform autofocus (FAST), do image stabilization (also fast!), and be able to stop down at a flick of a switch. And be hand-holdable. None of that applies to telescopes.
BTW, I doubt that any of the telephotos get anywhere near the correction of a wold class APO. Both color or spherical aberration wise. Try your 600mm f/4 L at 300X on Jupiter and report back (which is dead easy with a good 6" APO).