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SCT's have typically a 38% central obstruction at the baffle and give low contrast visual planetary images - its just the laws of physics.They also have a few more optical surfaces which all scatter light. The aspheric secondary mirror will also have less micro-smoothness than a flat spherical mirror. They are more useful for CCD imaging of planets where you are stacking lots of frames.
For visual observing - a good Newtonian with 20% or less obstruction performs almost as well as an equivalent sized retractor at a much lower cost. You may need to buy a tracking platform if it is on a Dobsonian mount or fit a servo -cat drive to keep the image centered while observing at high power.
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