Farpoint Tri Bahtinov Mask for Celestron 11 Inch SC and EHD

The advantages of the Tri-Bahtinov mask:

You can clearly see when you have reached the optimum sharpness - no more tedious guesswork is necessary.

It is three Bahtinov masks in one, rotated 120 degrees. It gives you three lines and three crosses to check collimation along three axes simultaneously.

So in addition to focusing, the Tri-Bahtinov mask also shows the collimation status along the three axes.

This is interesting e.g. for Schmidt-Cassegrain telescopes, where the collimation is done by push-pull screws of the secondary mirror along the three axes.

Positioning the Tri-Bahtinov mask along these axes will not only give you an overview of each axis of focus, but also how different these focus points are for each axis.

The Bahtinov mask is a less expensive method of focusing objects in the night sky compared to a standard motor focuser.

With the right mask and setup, it is easy to focus a star crystal clear in less than 90 seconds.