Home Made Bahtinov Focusing Mask, Templates

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2024-11-07 16:30:09

Focusing mask which was invented by Pavel Bahtinov is one of the easiest, fastest and accurate tools for focusing in astrophotography. During the focusing procedure the mask is placed in front of telescope's aperture, which is pointed to a bright star. Bahtinov mask produces 3 diffraction spikes: Two of them form an "X" shape, and another spike crosses it, forming a "Ж" shape. According to focus position - the central spike moves left or right (relative to the diagonal "X"). When precize focus is achieved - the pattern becomes symmetrical.

This method is very sensitive, since the displacement of diffraction spikes is apparent even with slightest focus shifts. It can also be used while focusing telephoto camera lenses for astrophotography. Bahtinov method can often be more convenient than reading a software generated FWHM value, because the human brain interprets geometrical shape faster than a numerical value. Bahtinov mask is superior to "Hartmann" focusing mask, its predecessor, however it is more complicated to make. While there are many comercially available options - It's not too hard to build it.

I have generated printable PDF templates for the most popular telescope apertures using the original bahtinov mask generator from "Astrojargon" website. Adobe PDF reader can be used for printing it. In printer settings make sure to select the correct page size (A3 or A4), 600dpi resolution and set the scale to 100% (or select "actual size"). Note that for larger apertures you'll need to print a "mosaic" of several pages, and then connect them together. Each page has 1 inch overlap and markings which may help connecting the pieces.