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Well I got the plate rolled, and dropped around Peter's place on Friday to do some drilling and tapping. Must say I really appreciate his help, and his knowledge/experience with this metalwork stuff is way beyond mine.
So here's some pics. As I said in a post somewhere above, the plate is 3mm aluminium plate, 150mm wide, 300mm long (about a third of the circumference). The edge of it closest to the front end of the scope I kept just below the secondary spider connections, that's why the focuser hole is offset. Got the metalwork shop to just provide the plate, put a 65mm dia hole in it, and roll it to the right curvature. They did a pretty good/accurate job.
When we first put the plate on the inside, there were some issues where we didn't think they'd rolled the plate to the right dimensions. Then we realised that the original finder bracket connection point has a thin stiffening plate around it that we hadn't seen because I'd covered in with flocking a long time ago. Duh.
First shot shows the outside of the OTA. Just added the 2 holes on the left there for one end of the stiffening plate, the 4 around the focuser hole are original. There's another 2 for the other end of the plate.
Second shot shows the tube side of the plate. The holes around the focuser are just holes (ie not tapped) so the screws that connect the focuser mounting plate will fix through it, clamping the focuser to the stiffening plate. The holes in each corner of the plate are tapped so that the screws can be bolted directly to it. We also oversized some holes for the finder mounting.
Third shot just shows me holding the plate on the inside, painted matt black but will be putting flocking over it as well.
Fourth shot shows the plate connected just via the outside 4 screws for now. I need to order longer ones for the Moonlite mounting plate, because they're about 3mm too short now due to the plate thickness. You can see I didn't make the plate as wide as the original one on the OTA. This was to minimise openings in the plate, maximising stiffness. It's just enough to allow the focuser drawtube through it plus minor tolerance.
Final shot just shows it from the inside, waiting for the focuser to be attached, flocking to be added.
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