Reading tells me that the Fraunhofer diffraction pattern exploited by the Bahtinov simply relies on three differing direction linear obstructions of any size or number, the limiting factor being simply the amount of light available to create a large and bright enough pattern to see at the magnification you are using.
I read that you can use three sticks tied together in any distribution , shape and width if the aperture is sufficient , the magnification is sufficient to reveal the pattern and the star is bright enough. In focus the diffraction pattern will cross. There are lots of different masks that exploit this effect.
The fishing line opens the pattern and increases the amount of light for a 100mm retractor while the number of lines add up to a visible pattern on a bright star at full live zoom on my DSLR. I imagine you could cnc cut a very open 1mm wide line pattern in aluminium and achieve a similar or better result. A formula can be downloaded to produce an image of the required mask, imported into cad and then copied at the correct scale for the material used, which is what I have done.
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Originally Posted by Averton
Hi Ray, It appears that the mask construction isn't as critical as some of the information we had read indicated as both our attempts are working. Your fishing line version sounds very interesting. If you get a chance, a pic would be great.
Peter & Clare
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