This solar filter holder is made for the Explore Scientific Maksutov Newton 152 Comet Hunter.
It also fits the Esprit 120 perfectly.
All holes in the design are intended for Ruthex threaded inserts.
I used M4x10 thumbscrews for clamping on the dew shield and M3 buttonhead screws to secure the front ring on the holder (puncture the solar film first).
I printed this in PETG.