Bahtinov mask

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Bakhtinov mask for a ten-inch model
Principle of the Bakhtinov mask

The Bahtinov mask (also Bachtinow mask , after its inventor Pavel Ivanovich Bachtinow ) is a focusing aid for amateur telescopes, similar to the Hartmann mask . The Bakhtinov mask is required for astrophotography , as it depends on the highest accuracy when setting the focus . The Bakhtinov mask is placed in front of the foremost optical element and creates a ray-shaped pattern in the viewer's field of vision. The more precisely the ideal focus point is set, the more centrally the longest of the rays can be seen. When the image is completely symmetrical, the focus is reached. Due to the large number of slot-shaped openings, a relatively large amount of light reaches the observer; Due to its low light intensity, however, the dummy cover is more suitable for use on bright stars.

However, the manufacturing effort can be disadvantageous in self-construction, since the corresponding number of slots must be cut from a sufficiently rigid material. In addition, the number, position and size of the slits depends on the focal length and the opening of the respective instrument, so that a new Bakhtinov mask has to be made for each additional telescope.

With the help of a 3D printer and ready-made templates, however, the effort or costs for a purchased product can be greatly reduced.

  • Simulation of the diffraction pattern of the Bakhtinov mask during focusing

  • Image in the camera viewfinder or eyepiece

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