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Depends on the ISO and the light pollution of your locale.
This is where you're going to discover just how painful this telescope purchase of yours is going to be.
For any pleasing and/or meaningful results, given a focal ratio of f/11, each sub-exposure is going to have to be between 10-20 minutes each. Anything shorter and you're not going to pick up enough signal.
This is why people start on short focal length instruments, whether they be reflectors or refractors; to cut their teeth; learn the vagaries of imaging, and, once perfected, or at least on solid ground, move on to longer focal lengths.
It's like Olympic-standard smokers -- they don't start out on two packets a day; they work at it until their lungs just don't notice anymore.
H
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