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Old 06-10-2019, 01:08 PM
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Rigel003 (Graeme)
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Join Date: May 2006
Location: Adelaide, South Australia
Posts: 1,059
I have a C11 and a premium 175mm refractor. Visually, I would much rather use the refractor on the moon and planets. After a modest cool down period you get perfect images with great sharpness and contrast. Magnifications of 350 - 400x are routine on nights with reasonable seeing. However... it's a very big and heavy tube and a chore to mount, eyepiece position is close to the ground when the planet is near zenith, and it needs a substantial mount for the long tube to be completely stable. It also costs $$$. And despite the perfection of the images, it is only 7" of aperture so there is a limit to resolving power and images dim at very high power (especially noticeable with Saturn).

If you're interested in planetary photography, the SCT is undoubtedly the better choice. The larger mirror gives better resolving power for fine detail, better colour saturation and overall brightness. The increase in light enables you to use shorter exposures and a higher frame rate which will generate more good frames for stacking and a larger image scale. On the other hand, despite my best efforts to cool it well, the SCT will very often be limited by thermal equilibrium issues from giving its best. The number of nights when it really comes up with the goods is small whereas the refractor throws up the best images the atmosphere will allow, night after night.
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