TRI-Bahtinov Focus Mask - Celestron Guidescope 5") Inside Dimensions 432mm x

5") Inside Dimensions 432mm x 273mm x 273mm (17" x 10

Item Number FCD100–127075–02 Focal Length 952mm Focal Ratio f/7

no-tool set up

But as you survey the image

and center the camera over the eyepiece using the knobs

TRI-Bahtinov Focus Mask - Celestron Guidescope 5") Inside Dimensions 432mm xWhat is the Tri Bahtinov? Essentially three Bahtinov masks in one, rotated over 120 degrees. It gives you three lines and three crosses to check focus and collimation, along three axis simultaneously. In addition to focusing, the Tri Bahtinov so also indicates collimation status along three axis. This is interesting for e. g. Schmidt Cassegrain telescopes, where the collimation is done by push pull screws of the secondary mirror along three axis. When