Celebrating 20 Years of the Bahtinov Mask

The first design, on the right, which quickly became known as Bahtinov's mask.

The 22nd September 2025 will mark twenty years since the first Bahtinov mask design was published by Pavel Bahtinov on the forum astronomy.ru. [1]

Over the last 20 years, the Bahtinov Mask has proven itself as an extremely useful focussing tool for astronomers, suiting any type of telescope and any camera lens with sufficient focal length. (One limitation of Bahtinov masks is that at short focal lengths the required slit spacing becomes very narrow, which makes it difficult to make Bahtinov masks which are effective for focal lengths of under 100mm.)

A Tri-Bahtinov Mask made by Astro Printer.

To find out more about the history and physics behind the Bahtinov mask, see this article that I wrote a year ago.

I have also previously shared a video of an interview that Bahtinov gave in 2018.

A later innovation was the adaptation of the Bahtinov mask into the Tri-Bahtinov mask in 2016, by C. Y. Tan and Satoru Takagi. The Tri-Bahtinov mask is a combination of three masks, as the name suggests, which creates three sets of diffraction spikes. [2]

The Tri-Bahtinov design can be aligned with the three mirror adjustment screws on a reflector telescope, allowing astronomers to both focus and collimate using this mask.

Thank you to those who invented these designs, and made them publicly available for all astronomers to use!

References/ Useful links:

1. https://astronomy.ru/forum/index.php/topic,10421.0.html

2. https://www.cloudynights.com/topic/536410-a-tri-bahtinov-mask-for-sct-collimation-and-focusing/