365Astronomy 2" SCT Eyepiece Holder
365Astronomy 2" SCT Eyepiece Holder with Compression Ring for SC Telescopes
Comes with a 2" SC thread to connect to a Celestron or Meade Schmidth-Cassegrain telescope.
One screw would secure the inserted accessory via a compression ring that might be enough, but we'd be happier if it had two or maybe even three screws. Thumbscrews are available separately, so additional one or two threaded holes could be added by the user making this device a very cheap alternative to much more expensive products.
In any case, if you just use it with one screw, please make sure that you secure the accessory well, especially when you point it into the zenith.