>>3311584What about focal length? My biggest scope is 2800mm f/10 (pic related).
f/9.4 max aperture is slow as far as lenses go, but pretty standard for telescopes. It doesn't mean it's anything other than very shallow DOF at these focal lengths, though; there is a massive difference between 100mm f/8 and 3000mm f/8!
With my 2800 f/10 at minimum focus distance, you can actively shift the DOF down the length of a leaf, it's that shallow. Pretty much razor thin, and useless for anything that isn't perfectly flat. It's why the technique of shooting a subject in front of the moon and having them both in focus only really works when the subject is far away, at infinity focus. You can stop down all you want to no avail, generally speaking. Much better to place your subject close to the infinity focus of the optics. That way, as far as the optics are concerned, the moon and the subject in front of it are the same distance away. It can't tell the difference between 500m and 384,000km.
