On Tuesday, I did a fair amount of stuff. First I cut the focuser hole in a 5x5 x 1 inch piece of Birch and mounted an Astromart Feathertouch focuer to the board and made the bracket to mount it to the upper ring of my 16 inch Strut scope. Then I loaded up some tools, drove up to our place in the high desert..
When I got there, I made a cover for the mirror box for my 12.5 inch. I had a piece of quite nice 0.325" plywood that had showed up with something I had bought.. I cut it with the Saber Saw and glued it it all fit fine and dandy. It was a nice replacement for the cover I had been using for the past 8 years, a piece a foam sleeping bag pad.. doubled.
Then I went about mounting the focuser board to the upper ring. I took awhile. I set position by clamping the board to upper ring and focusing on the moon until I had enough outward travel with the 41mm Panopic and no Paracorr. That night I worked quite nicely, a nice upgrade from the GSO focuser that was on the scope. But I realized that the larger bore of the Feathertouch was allowing some light in and I was having problems with ghosting from the moon. I wasted some time working on that when I should have been observing.
The next morning I was pondering the problem, it really called for a larger baffle which I did not have. The GSO Focuser with it's 2 inch straight bore and longer drawtube did not have this problem.. I decided to unbolt the Feathertouch and see what it looked like with the GSO. I needed to lower the GSO about 1/4-3/8" and was looking around for a shim and realized that the 0.325" plywood was perfect.
Then I had a brainstorm and realized that I could use one of the leftover pieces from the mirror box cover project to stiffen the upper ring where the focuser mounts, I had enough to span the distance from one strut to the next. The next few hours were spent cutting the contour with scroll saw, sanding it and mounting it. It's screwed in place and also held by the focuser board bolts. The original 0.70" upper ring hadn't been stiff enough and for about 7 years I had used an upper ring made from laminate pine but it broke so I had been using the thinner upper ring.
It all worked out very nicely. The workmanship is crude but effective, the focuser board and upper ring are much stiffer, since most such bending stiffnesses are 3rd power of the thickness, going from 0.70" to 1.02", it should be about 3x stiffer.
Wednesday night, it was again clear. The ghosting problems were gone, the focuser board was noticeably stiffer and the scope, it seems like after more than 8 years, it's still getting better. The next step.. switching back to the Feathertouch..
In the photo, the reinforcing plywood can be seen and also on the strut on the right is a 1 lbs sliding counterweight. It's just a piece of heavy wall tube painted and drilled for a nylon locking screw. It works very nicely to balance the scope..
The long term plans, take a wood working class....