The image below shows my original modified Hartman mask on the right and my first draft of a Bahtinov mask on the left, both are from my SN6. The respective focusing pattern (an average of 0.1sec exposures of Altair using my DSI Pro) is shown below each mask. The pattern from the Bahtinov mask is much brighter and it is much easier to judge when the best focus is achieved.

This example Bahtinov mask was cut from black foam core art board using 5mm slots and slats. The angle of the reference slots are +/-20 degrees from the centerline (40 degree total internal angle).

My next task is to make a mask for all of my telescopes and see how well this works visually.