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The big central obstruction in the SCT relative to the smaller one in an equivalent reflector affects contrast and sharpness. Check it on a star at high power, more light goes from the central star disc out into the diffraction rings.
My MAKs and SCT are never as contrasty on the planets as their equivalent sized reflectors are. That's just the physics of the design, it sacrifices some optical properties for the convenience of a handy, very versatile and easy to handle and use telescope.
If you want sharp contrasty images from the C14, perhaps make an aperture mask (5 or 6" diameter) which just misses the central obstruction and goes out to the edge of the mirror.
Regards,
Renato
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