Thanks Olly. What I referred to as excessive magnification was the image size presented by telescope simulators such as Telescopius, when using a large focal length scope and various DSLR and astro camera sensors. This appears to show image size has an inverse correlation with sensor size for a given focal length. As such the focal length is the determining factor. This then suggests that a scope such as my 8SE with its large focal length is sub-optimal for all but the smaller DSO's. However that is by definition unlikely to work with the alt-az mount and field rotation This and the fact that the 8SE is almost at the mount's weight limit and the conclusion I draw is that using an 8SE for this purpose is a bad plan. This is especially the case as I did also consider a piggy-back mount to carry a camera on the 8SE. I did buy the 8SE for visual use so all is not lost. The next step is to look at alternatives or perhaps try a camera, alone, on the mount and see what can be achieved.