Troy,
thanks for that. When you say (of the fly) it may have been taken at maybe 2:1 or 3:1, am I thinking right when I say the lens can be adjusted from 1:1 up to 1:5, and that a shot taken at 1:5 will be magnified 5x, or am I reading it wrong?
I think I'm expecting too much too soon. I remember all the astro terms were meaningless at the start, then it all begins to make sense slowly but surely. This will be the same, so I'll study what's already been provided and doubtless all will be revealed in due course.
Cheers
PS - Thanks for the links too - that's great !