This adapter serveres 2 purposes besides the obvious one: The whole assembly of adapter and collimator can be checked for collimation together and it can also be collimated as one item removing possible adapter/collimator misalignment from the list of possible issues.

Printing and slicing

Make sure that seam on the 2 cylindric surfaces is in the prepared groove. Slicer should put it there by default. Otherwise a print seam that is protruding out  is going to mess up alignment in the focuser. 

Assembly

Assembly is press fit. Apertures are slightly flexible.

Onshape source

Support

All my work is free and in the public domain when possible. If you find it valuable, you can support me on Ko-fi.

Telescopes collection

If you are interested in other telescope and astronomy related items that I have made, have a look at my Telescopes collection here on Printables.