Visual back for ETX scopes and C90 Orange Tube

thingiverse

After stumbling upon a post on reddit, I decided to dig deeper and discovered that the back port on the ETX and C90 is largely identical. For reference, it roughly measures 1 3/8 inch x 24 tpi in non-metric terms. After making some quick adjustments, this design works well on both models. The threads are almost identical, with the C90 having a slightly larger diameter. You may need to tweak the etx_thread_extra_clearance and eyepiece_extra_clearance settings depending on your printer model. Some eyepieces require 0.2mm clearance, while others demand more. Be patient when first using this design – it might take a few trials to get it right. Avoid forcing it too much, as this can lead to problems. However, with a few on and off cycles, it should clean up nicely. This model utilizes Dan Kirshner's threads.scad library.