Collapsable tube?Posted By Alex McConahay |
If I follow your question, there is no need for a tube at all around a telescope. My twelve and a half inch dob has a ring of half inch plywood at the top, from which hangs a focuser, a spider to hold the secondary, a little bracket to hold the Rigel Quickfinder, and four brackets to anchor the tubes coming up.
I have seen designs where the primary is virtually naked. THe bottom of the tubes attach to a metal frame that connects to the mirror cell and the bearings.
Now, I prefer having at least cloth around the trusses and mirrors to cut down on stray light. (I don't like bare mirrors). And you do need something to hold the top a given distance from the bottom. A tube does both these things well (but then take a lot of room when stored!).
So, as I said, one does not need a tube at all. (ANd tubeless scopes can be easy to store.)
Alex
I have seen designs where the primary is virtually naked. THe bottom of the tubes attach to a metal frame that connects to the mirror cell and the bearings.
Now, I prefer having at least cloth around the trusses and mirrors to cut down on stray light. (I don't like bare mirrors). And you do need something to hold the top a given distance from the bottom. A tube does both these things well (but then take a lot of room when stored!).
So, as I said, one does not need a tube at all. (ANd tubeless scopes can be easy to store.)
Alex
