Adjustible Bahtinov Focus Masks

Adjustible Bahtinov Masks have grommets and pegs that adjust to fit on the end of your dew shield or OTA. To fit on your OTA (without a dew shield) there must be nothing (like a SCT secondary holder) projecting out from the end of your OTA. But distance from the optical train is not a critical factor in Bahtinov Mask performance, so you will never have any issues with putting an adjustible mask on the end of your dew shield. It is often more convienient to use on the end of your dew shield, especially if you are have to manage camera cords, etc. in astrophotography.

Measure the diameter of the outside of your dew shield (or OTA) and select your Adjustible Bahtinov Mask size accordingly. For more information: https://youtu.be/65TLAzl75lw