Hi Ed,
Thank you for the advice. I'm certainly interested in AP but I think that I won't be diving in at the deep end just yet.
Since I'm a naturally inquisitive person who enjoys research, I already have a list of questions and am slowly filling in answers. Of course, most of the answers raise additional questions. But that's where the fun lies.
I'm looking forward to learning the sky visually for the time being. (But it probably won't stop me designing and building a "toy" GEM
- looks like it might be an interesting exercise.)
One thing, however, that I do need to do some more research on is that I understand that many (most?) of the commonly available newtonians have insufficient back focus for a DSLR to achieve prime focus. As well as my Nikons, I also have two µ 4/3 cameras which have a significantly shorter flange distance. Perhaps that might allow for at least some lunar and planet photos inexpensively.
Thanks for the links, Ed - I'll investigate.