Better alternative to Bahtinov Focusing Mask - ATM, Optics and DIY Forum - Cloudy Nights
Farpoint Astro Bahtinov Mask for Celestron 9.25" SCT
Amazon.com : Astromania Bahtinov Mask Focusing Mask for Telescopes - FM200mm for a Tube Outer Diameter (OD) from 215mm-260mm - can be Mounted with The Brass Screws Inside or Outside The drawtube :
Which is the best alternative to the Bahtinov Mask - Carey or Tri? - YouTube
a Modified Bahtinov mask used for finding the focal plane precisely. b... | Download Scientific Diagram