I did find, again, that the point source of light had to be fairly bright to be able to see the diffraction patterns. But once I could see them, I thought it time to try the Bahtinov Grabber software.
Moved the EOS Utility camera control window to the top-left of the laptop screen. Put the Live View window at the top-right. Zoomed into the star. In the zoomed display, increased the level to 200%. With Live View in simulated exposure mode, I increased the speed and dropped the ISO to darken the view. Adjusted the Live View controls so that I could see the 6 spikes while not perfectly focused.
Launched BG. Put it at the bottom-left of the screen. Ensure the rotating focuser setting was off. Turned the sound off. Ensure I had the correct focal length (0.018 metres), diameter (0.003 metres), and pixel size (5.7 microns). Set the capture area to grab the image from the 200% Live View. It worked! Woo hoo!
OK. I didn't have significant doubts but it was good to see that the capture method actually worked with the Canon software. Another hurdle crossed.
I could see that BG was detecting the diffraction lines. I continued focusing with the Live View controls. I had not considered it before but I focused concentrating on the Live View and made the image better, to my eye. Tried to get the middle diffraction line perfectly centred. Meanwhile in my periphery, I could see the yellow concentric circles appear in the grabber software, meaning it liked the focus too. Neat. I could see I was improving the focus; the software was instantly confirming it for me.
Immediate positive feedback. And I had stumbled into a better workflow.
I gently, slowly removed the focus mask. It came off easily. I snapped a photo. And enjoyed a well-focused shot of the test star.
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