UPDATE4: Included the SCAD source files. Note that the "threads.scad" is a dependency needs to be placed in the same folder as the other. I will cleanup these files, for now just dumping for people to use it.
UPDATE3: Model for DSLR internal taper is now longer (instead of a 45deg it runs from male thread to female thread), which makes it more sturdy against compression when installing on the telescope and that goes without losing any field of view.
UPDATE2: Included a model for attaching a DSLR using the m42 thread. For stability and robustness, 2mm has been added to the walls and the coupling is reinforced by a tapered section. Male thread is 5mm long and the remaining extension is 22mm.
UPDATE1: Revised the threads to be with a pitch of 0.75mm instead of 1mm! And also the female thread and outer diameter have an offset. Now the parts will fit almost perfectly (when print does not fail). Model is also smaller and more compact. Squared version is prefered.
Adapter primarly designed for holding a 48mm filter in front of ZWO cameras that have a m42 T-thread and a 2 inch outer diameter. Not designed to hold the weight of a DSLR. M42 male thread is 2mm high. M48 female thread is 2mm high. Tapered section is 3mm high.
There is a "'squared" version where the tapered section is replaced by a 1mm thick flat and square section. It may be the best choice for stability, but supports will have to be used. Otherwise the other version is overhanged at 60deg which may work without supports.
Testing with PETG filament with 0.1mm layers. I don't know about side effect when used in freezing temperatures or cold damp nights.
Not responsible if things go wrong with your equipment, please test carefully with the expensive cameras and filters.