Farpoint Adjustable Tri-Bahtinov Mask — 11" to 14" OTAsNot sure this is the right mask for your telescope? Use our Focus Mask Finder match your scope to the right Standard, Tri Bahtinov, or Hyperstar RASA mask. Adjustable Tri Bahtinov focus and collimation mask for OTAs from 11" to 14" front aperture. Sets onto the front of your telescope, gives you focus AND a collimation check from a single short exposure, and lifts off cleanly when you're done. The adjustable peg system fits any scope in this aperture