Astrozap Bahtinov Mask for 139 mm to 216 mm Diameter

Bahtinov Masks for convenient and exact focusing of your Astro Images

The Bahtinov Mask is named after its inventor Pavel Bahtinov. This focusing tool enables precise adjustment of your Astro pictures to the focus plane of your telescope or camera lens.

Attaching the Bahtinov Mask to your telescope or lens is very simple. Each mask is supplied with 3 screws. Remove the plastic from the screws, put them through the designated holes and then pull the plastic covers back over the screws. Now you can attach the focusing mask to your telescope or lens and start focusing.

This is how focusing of your camera on your telescope or lens works.

Attach the mask to your telescope and slew the telescope to a bright star.

Turn on your camera and watch your selected star on the live view screen.

If the image isn´t yet in focus, the central line of the Bahtinov pattern is shifted. Adjust your focuser until this very line sits exactly inbetween the other two lines.

Now you have achieved optimal focus. Remove the mask from your optics and you can start the exposure of your object.

Practical advice from Teleskop Service

Using a Bahtinov Mask for focusing works especially well for Deep Sky photography. Correctors and Barlow Lenses are not a problem.

Ideally you want to use a star with medium brightness for focusing. It should neither be too dark nor too bright. The lines of the Bahtinov interference pattern have to be clearly visible.

The chosen star shouldn´t be positioned in the center of your live view, because most telescopes or lenses, although corrected, do not produce a plane field of view. We recommend to position the star in the outer third of your image. That way, you will achieve a better overall sharpness across your field of view.