Celestron C5 Duncan Mask

thingiverse

I tried one or two other C5 Duncan masks but they didn't fit so in the end I just made one from scratch. It has little cutouts along the edge because my scope has protrusions there to match the dust cap. Included is also a "minimum viable print" test piece. If you print it you can see if it fits your C5 before printing the full body version. For my C5, the inner hole is 45.7mm and friction fits. The outer diameter is 140.3mm and leaves a bit of room because the the C5 tube is not exactly centered around the inner collimation part (the 45.7mm part in the middle). See http://alpha-lyrae.co.uk/2013/12/31/schmitt-cassegrain-collimation-made-easy-using-a-duncan-mask/ for more info on Duncan Masks.