Bhatinov bright star mask for an Apertura 75Q telescope to aid in focus adjustments. 

Idea from https://www.nebulaphotos.com/resources/bahtinov/ 

Used https://astrojargon.net/ to generate the mask then converted from svg file to dxf format with https://inkscape.org/ and finally created a 3D CAD in OnShape for the cover and rim and exported an STL to print on the Bambu X1 Carbon.