A one part Cheshire-style collimation eyepiece (1.25 in). More effective than a standard pinhole collimation cap, especially when lighting is not optimal.

Update 02-2025:

Added a version of the eyepiece with crosshairs. Make sure to print in the correct orientation (crosshairs on the build plate)!

Usage Instructions

Install it on your scope then shine a light into the bottom of the eyepiece (on the angled surface) through the hole. You'll see the eyepiece's reflection very clearly in your main mirror when looking through the eyepiece's pinhole, which will help you center the eyepiece in the main mirror by adjusting its collimation screws. If you plan to use the telescope immediately afterwards, I'd suggest shining a red light into it to try to preserve your night vision as much as possible!

Printing Instructions

Print standing up with the front of the eyepiece (the part where you look) on top. Prints without supports but depending on your printer and the material used the underside of the circular opening might need a tiny bit of cleanup. I left mine as-is in the photos. Printed with PETG for heat resistance.