Except on the best of nights, the 7D will be oversampling. It would work well on a nice refractor well below 1000mm focal length
If you're finding it troublesome, then go for a cooled astro camera. The noise can then be reproduced in dark frames and subtracted from the images (calibration).
An 8" SCT is not designed to work with a full frame camera, and you will see pretty dramatic light drop off in the corners of the image, so be prepared to crop heavily.