I have been active in photography for more than 50 years (!!!), using an Argus C3 and building a darkroom when I was in grammar school. I have been primarily using Nikon single-lens reflex cameras (Nikon F, F2, F3) and Nikkor lenses. I have a small collection of Nikkor lenses which are useful for astro-imaging - either due to their relatively long focal length, or due to their fast speed (f/1.4, f/2.8). For example, the lens pictured above is the "Reflex-Nikkor 500 mm", which is basically a catadioptric telescope design that makes for a very compact size in this long focal length. Other views of this lens are shown below: (yes this lens is as dirty as it looks - not cleaned for several years; hopefully, I won't find any mold when I finally clean it!)