Actually a person can get Airy disks (diffraction spots) nearly as perfect as they get with a garden-variety reflector. Just make an off-axis mask and you end up with perfect color correction (something even triplet APO's don't have) as well as no central obstruction diffraction artifacts. With larger Newts especially, you will have plenty of aperture with the off-axis mask for planetary and close double-star work. Then just remove the mask when you're ready for DS work, when you really need the light-gathering power of the full aperture. Truth be told, however, a long-focus Newt with minimal diagonal obstruction doesn't pull as much energy from the central spot as most people think. You have to determine if the obstruction diffraction offsets the reduced aperture (and thus resolution) of the off-axis mask. Remember that the smaller the aperture, the larger the Airy disk, so you can take a double-whammy in terms of resolution. Match your optical system to your targets.