Filter Adapter for mounting 2" M48 filters on 77mm objectives

thingiverse

I needed an adapter to mount my 2" astronomy filters on my Samyang 135mm. The thread sizes are M48x0.75 and M77x0.75, respectively. For v1 I added tiny holes to help screw the adapter on the lens. ----------------- Update v2: v2 now has a rugged helper ring designed to help screw the adapter on the objective and to allow the lens cap to be attached directly on top of the whole assembly (objective+adapter+2" filter). The top rugged part has quite some stringing issues on my printer for now. Don't know if it's my old filament or the design itself. Will update slightly for v3 to improve printability. ----------------- Update v3: there was some room for both the external and internal diameters of the rugged helper ring, I made it slightly larger in both directions. It is more sturdy now, and prints better as well. I made a final print at 0.12mm layer height that looks beautiful! -------------------------- In general: The threads come out quite nice, the tolerance is tight obviously and you may have to play with horizontal expansion. What works best on my ender 3 V2 is a horizontal expansion of -0.02 (to adjust the M77 thread tolerance) and a horizontal hole expansion of 0.18mm for the 2" filter. Note that they add up and this gives me a 0.2 total hole expansion. It seems to be better with random seam position (this prevents having the seam defects concentrated in a single position which seemed problematic). Clear skies!