The focusing mask according to Pavel Bahtinov facilitates precise focusing, which is particularly important in astrophotography. The mask is attached to the front of the tube or lens. When looking at a star, it produces a pattern of rays. When the long ray intersects the two slightly shorter rays symmetrically in the middle, the focus is correct. Thanks to its many opening slits, the Bahtinov mask can also be used with relatively dim stars. This is an advantage over the classic Scheiner mask.
A Bahtinov mask should actually be calculated separately for each aperture ratio. However, experience shows that one mask can be used very effectively for an entire aperture range.
This Bahtinov mask is equipped with a filter thread. Please make sure to select the size that fits your camera lens.
With a Bahtinov mask, focusing is really easy and reliable: turn on the camera, point it at a bright star, activate Live View on the camera, screw the Bahtinov mask into the filter holder of the camera lens, adjust the symmetrical diffraction pattern, remove the Bahtinov mask, and start shooting!
