The mirror bowl


The mirror bowl


The mirror bowl


The mirror bowl 		The mirror bowl follows the exact design that was worked out by Randall Wehler in the Sky and Telescope article. I ordered a Smoky Mountain Cooker bottom from Weber and than sawed off vent hole covers. I originally used a lid and had steel shelves welded into the bowl to provide a shelf for the first plywood ring. Unfortunately, the welds buckled the outside of the bowl and ruined the smooth finish necessary to fluid movements. My second base was the bottom, which had no handle to be removed. The first base had no holes to bolt in the top ring of the base assembly and so four holes were hand-drilled. The new base had three holes already drilled but in a slightly lower position.

The very bottom of the bowl (first image) has a 25 lb. barbell weight purchased from Big 5 velcroed in at an angle to provide a counter weight and counter balance to the top ring assembly. I also purchased four 18" plywood rounds from Builder's Discount in San Francisco. The first plywood circle was cut to about 15" in diameter with a 10" diameter hole in the middle and a Flats-No-More bicycle innertube glued to the ring (second image).

The second picture shows the first plywood ring along with the bicycle innertube. This provides a base for the "mirror cell" which is a plywood circle with a shallow hole routed out of the center and a foam rubber pad in the mirror hole.


The third picture shows the solid plywood circle with a cavity routed out to hold the mirror. The foam pad rests underneath the mirror to provide a surface that is in full contact with the mirror. Without the pad, the mirror is resting on only a few points. The square metal brackets are to keep the collimation screws from digging into the wood. The screws apply pressure to the innertube on the bottom ring to correctly position the mirror. Also visible in this shot are three wooden brackets that are used to hold the mirror in place and three plywood shims to keep the plywood circle centered. I did not use any mirror clips.
The fourth picture shows the mirror on its plywood shelf in the bowl. You'll note a piece of white tape used as a marker. I ended up using velcro markers throughout the whole assembly do aid in proper

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