Thank you, Dennis, for sharing this "revolutionary new way of focusing".
And thank you, Adam, for posting the work you have done in testing the method. I copy/pasted your refractor pattern to Photoshop and sized it to fit the cell that I made for a Hartmann mask.
Last night was clear with "not so nice" seeing and transparency.

I used the Bahtinov mask on a Megrez 110 (focal length 655mm...f/5.95) in visual mode first and the results were great.
I then attached my Canon 350D with a 2.5x angle finder. If I remember correctly, the first,out-of-focus star is Vega and the fainter, closer-to-focus star is Alpha Ophiuchus (mag 2.09).
It was very hard to see the focusing pattern in the camera's finder so I adjusted focus until the faint "line" was sharp. My results are shown below. You can see that the first exposure is slightly off but the second is pretty close. The "test" images below that were taken at closer-to-focus. M13 at 30sec and M27 at 150sec. Both are unguided.
Because the camera viewfinder does not clearly show the focusing pattern, I'll still have to "shoot and check" but it will be a lot more accurate.
A big "HOORAY" to Pavel Bahtinov for sharing this with the astro community.
"Jerry-rigged" test mask
Out of Focus
Closer-to-focus
M13...30 seconds
M27...150 seconds