Thanks, Jerry, for the reply. I did play around with the exposures the other night. I found with a bright star a reduced exposure gives a better image for focus. It reduced the size of the central star in relation to the spikes and allowed made it easier to judge when the spikes were centered. I didn't try it on a dim star with a longer exposure.
I did read all the posts but it was 2 sittings and it did take a while. It's good stuff, though.
Does the screen absolutely need to go over the front of the telescope or could a smaller version be placed elsewhere in the imaging path? I'm wondering about a reduced 1.25" version on a 1.25" clear filter to allow use remotely by rotating that filter/screen into the optical path as we do with color filters. It could be made accurately with a photo etch technique.
I've found yet another way of making a screen for a larger telescope, this one is for an 8" f/6 Mak-Newt. I used a router and a pattern bit. I printed the pattern and contact cemented it to a 1/4" MDF. I rough cut the openings with a band saw to remove most of the waste. I don't have a surrounding support on this one so to avoid closed slots, sawed through the edge of the filter so the slots are now open (looking like a fish skeleton) but leaving a bit extra on the ends of the bars to glue to a supporting ring later. I cut some strips of MDF the same width as the bars on the screen. Next I placed the strips on the black stripes on the screen and held them in place and drilled 1/8" registration holes through the strips and the bars, then inserted 1/8" registration pins to keep the MDF strips securely in place. Using a router and a 1/4" pattern bit with the bearing following the strips, it was easy to route straight lines to clean up the rough sawn slots. It worked pretty well. I wasn't able to go deeply into the "V"s with the router so cleaned those portions up with the band saw. I squared the rounded corners with a razor. After removing the strips and registration pins, I filled the 1/8" holes with some wood putty. It turned out pretty well. The screen is rigid and it didn't seem to take that much longer than the smaller one I cut from Kydex. I'll stain it black and seal it with some polyurethane, then affix a supporting ring.
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Re: Revolutionary new way of focusing! No less!
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