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The only advantage I can see for the GSO RC is that it is lower in cost.
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Of course your mileage may vary...this is from my own personal experience having owned 8 inch SCT (f/10) , 8 inch Newt (f/4) and 8 inch RC (f/8). I think f/8 is about the sweet spot for a managble 8 inch scope for imaging.
Benefits of RC when compared to SCT:
1. Faster cool down with open tube
2. No dew problems on the corrector plate
3. Fixed primary
- can be collimated
- holds collimation better
- better pointing accuracy
- way less differential flexure
4. Faster / shorted f/l - easier to guide.
Disadvantages of RC when compared to SCT:
1. Harder to collimate
Advantages of SCT and RC when compared to fast Newt:
1. Focuser and camera are in a more stable position (i.e. not attached to thin tube wall)
2. No offset secondary - defocused stars are always symmetric.
3. Backfocus distance and vignetting are easier to manage.
Some people will look the spot diagrams and make the decision based on that. Fair enough, but spot sizes don't count for much if you can't get the focus, guiding or collimation right in the first place.
James