Hello:
I recently finished the mirror cell for a 17.5" mirror, so I though I'd share what I came up with. It deviates from the standard Barry & Krieg mirror cell in a few ways. It has a triangular frame (an idea I shamelessly stole from another scope), where the collimation bolts will run though the corners of the triangle (haven't drilled those holes yet). Each of the triangles is on a see-saw bar, as I've seen done on a 6 point cell. One thing I didn't like about the Barry & Krieg cell design is how the bolts that hold the triangles stick through the triangle, and how the triangles sit on the flat top of a nut. I solved this by epoxying a machine screw to the bottom of the triangle, thus solving the problem of having the bolt pass through the triangle. The triangle pivots on the conical bottom of the machine screw head. The bolt passes through the see-saw bar to a lock nut on the other side. This lock nut isn't strictly necessary as the weight of the mirror will keep the triangles in place, but it's nice to know they're there. The hole in the see-saw bar on the far side of the triangle is oversized to allow the bolt to pivot about the upper hole. It was laid out by PLOP, then put together with nuts, bolts, and JB Weld, so it was quite quick and easy. Hopefully it'll work out well. Next: the top end ring. I welcome any comments or questions.
Cheers
Mike Connelley
I recently finished the mirror cell for a 17.5" mirror, so I though I'd share what I came up with. It deviates from the standard Barry & Krieg mirror cell in a few ways. It has a triangular frame (an idea I shamelessly stole from another scope), where the collimation bolts will run though the corners of the triangle (haven't drilled those holes yet). Each of the triangles is on a see-saw bar, as I've seen done on a 6 point cell. One thing I didn't like about the Barry & Krieg cell design is how the bolts that hold the triangles stick through the triangle, and how the triangles sit on the flat top of a nut. I solved this by epoxying a machine screw to the bottom of the triangle, thus solving the problem of having the bolt pass through the triangle. The triangle pivots on the conical bottom of the machine screw head. The bolt passes through the see-saw bar to a lock nut on the other side. This lock nut isn't strictly necessary as the weight of the mirror will keep the triangles in place, but it's nice to know they're there. The hole in the see-saw bar on the far side of the triangle is oversized to allow the bolt to pivot about the upper hole. It was laid out by PLOP, then put together with nuts, bolts, and JB Weld, so it was quite quick and easy. Hopefully it'll work out well. Next: the top end ring. I welcome any comments or questions.
Cheers
Mike Connelley
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