Quote:
Originally Posted by ausastronomer
If you want one scope for both visual and imaging they are a great choice and probably the best choice.
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Disagree on all accounts. Visually SCTs suffer from huge central obstruction. There is no way around that - you can have a perfect SCT optically (and they are nowhere near that) but damage to contrast transfer has already been done. Not really that objectionable on Moon or Saturn (rings), but any ultra low contrast feature (all of Jupiter, detail in Saturn belts and fine features of Mars) will be hard hit.
Imaging wise, SCTs are hard work because they are dreadful in keeping collimation (I have to check and usually recollimate every time I change elevation more than about 20 degrees with my C11); but main issue is enclosed primary which lags in temperature and causes internal heat plumes. Short of actively tackling that via pelitiers and internal fans, you are at the mercy of local temperature gradient. Quite often SCT users will report "bad seeing" while Newtonian and Cassegrain counterparts will work close to their maximum resolution - same place, same time.
The only real advantage of SCT is comfortable observing. Using binoviewer (compulsory for people with floaters like yours truly) and having comfy chair is a real game changer. I know you can use bino in a Newtonian, but they often end up in all sorts of neckbreaking angles and it is impossible to seat back and relax. Planetary observing is a waiting game, being comfortable is a definite advantage.
Bratislav