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I just drew one with Inkscape and printed on regular paper. I hope to try it tonight. After cutting out the gaps of course

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I did one last night for an 80mm, the quick and dirty way. I grabbed the graphic out of an earlier post in this thread, scaled it up to 80mm diameter, and printed it. took the printout, and an exacto, sat out on the back deck for 30 minutes making fine cuts. The idea was, dont worry about a 'perfect' mask, just 'good enough' to take a look and test the concept.

After I had the mask cut, I put the ST-80 (normally used as a guider, but fits the small tripod) on a tripod, pointed at polaris, with a Canon 300D attached. I used the motofocus to make very small focus adjustments (about 1/20 of a second, at the low speed). Not the most precise measurents, but, I know that those kind of button pushes on the motofocus will take around a thousand of them to get a full rotation of the focus knob.

I've done this test in the past with software to measure FWHM and try find focus with this setup. Results vary from sporadic to inconclusive. I've never seen FWHM measurements give a conclusive result with this ST-80 and a dslr, have tried numerous methods.

I have 20 odd jpeg fine shots taken as I walked the camera thru focus in those small increments. There is absolutely no question which one is best focused, and there is absolutely no doubt it is moving between shots.

If I dont get to it tonite, over the weekend, I'm going to take the time to do a better job of cutting, using a strait edge to make the cuts, and do a coffee can lid that fits onto the 127mm mak perfectly. Based on what I saw last night, focussing issues for the DSLR on these telescopes is going to be a thing of the past. I've got an SCT coming next week, and if this works on the mak as well as it did on the little refractor, the mask will be waiting for the SCT when it arrives.

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