Bahtinov Masks & 3D Printing

A few weeks ago I decided to have a go at 3D printing Bahtinov Masks for my telescope and cameras. The Bahtinov mask is a very handy device used to focus small astronomical telescopes and cameras accurately. They are readily available but can be a bit pricey when you take into consideration that several sizes are required, being a budget minded tight ass I decided to produce my own by modifying designs on thingiverse.com and printing them out on my printer. This is time consuming but costs almost nothing.

The mask consists of three separate grids, positioned in such a way that the grids produce three angled diffraction spikes at the focal plane of the instrument for each bright image element. As the instrument's focus is changed, the central spike appears to move from one side of the star to the other. In reality, all three spikes move, but the central spike moves in the opposite direction to the two spikes forming the "X". Optimal focus is achieved when the middle spike is centered between the other two spikes (see below).

Wikipedia images

So far I have tested the large mask on the telescope and the diffraction spikes are clearly visible in the eyepiece. I am yet to test the smaller versions on various camera lenses so I will update this post when that happens...