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Hi Geoff
Good points. I do remember some while ago playing around during a couple of imaging sessions where I compared the focus accuracy of the Bahtinov mask by eye versus using CCDSoft Focus Tools. Unfortunately, the results were polluted by an ill-fitting mask and some (since) discovered slop in my focuser.
However, even with the above anomalies, I judged that to all intents and purposes, eyeballing focus via the Bahtinov Mask on my computer display was as accurate as using the Focus Tools panel in CCDSoft, where the software produces a graph indicating best focus. This was based on using a manually operated, motorized focuser, not a fully automated software controlled process.
Having now got a well made mask and having since solved the focuser slop, I haven’t yet re-run run the tests. Like you, my previous experience leads me to believe that the Bahtinov Mask would appear much higher up on my own list, when viewed on a computer display.
In other experiments, I found that even using the Canon 40D in-camera “Live View” at x10 zoom gives a superb focusing image using a bright star.
Cheers
Dennis
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