Now that Pentax SLR cameras are a dying breed, the lenses for them go for next to nothing on eBay.  £30 later, I have six teleconverters to go with my old Hoya 75-205mm lens, in addition to a Pentax/Nikon adapter.  In short, I have a 20 metre focal length on my Nikon DSLR and while the speed/sharpness are going to be terrible, the cost is small.  While the Hoya lens is pretty good even by today’s standards (here),  this is a set-up that should make any photographer cringe:  7.2–19.7m @ f/256.

I had no problem photographing the moon – but finding the moon was quite difficult, since my tripod wobbled all over the place under the weight of all the glass above it.  Focussing the lens was also quite tricky at that distance, the lack of sharpness in the photos isn’t solely due to the amount of teleconverters that I was using.