Tri-Bahtinov Focus and Collimation Mask for Meade 12" SCT
Tri-Bahtinov Focus and Collimation Mask for Meade 12" SCT is an ingenious new way to easily focus a telescope. Pavel Bahtinov, a Russian amateur telescope maker and astronomer, created this simple, very intuitive method and the device has universally been named after him: The Bahtinov Mask.
You can read how to collimate using the Tri-Bahtinov Mask here: https://github.com/cytan299/tribahtinov
or here https://www.cloudynights.com/topic/536410-a-tri-bahtinov-mask-for-sct-collimation-and-focusing/page-16?hl=+tri%20+bahtinov