Thanks again for all the comments - I'm just using my D5500 DSLR and for most of these a very old, quite slow, Sigma 18 - 200mm lens. I took some other wide-field shots too, but I haven't got round to doing anything with them yet. All the processing was done using Lightroom and Photoshop - I have a Creative Cloud account so I like to get my money's worth! I'm hoping to get a copy of "Making Every Photon Count" soon which I believe in its latest edition covers Star Adventurers and other tracking mounts. I suppose eventually I'll end up with all the expensive equipment too, I just need to save up for it! My next purchase will be a much better telephoto lens, which I'll also be able to use for photographing wildlife.
Cheers,
Paul