The mirror cell, shown from the top (above) and bottom (below) is almost exactly what the Kriege and Berry book (Chapter 5) describes except that all the metal is bolted instead of welded.  This worked great.  Another change is that the two crossbars threaded for the 3/8 x 16 collimation bolts are of solid 1" aluminum bar (from Small Parts U-ZSA-16, page 98 of Catalog 21) because I was afraid that the thin steel of the other tubing only had room for a single thread and wouldn't be strong enough to hold the mirror. Another difference is the edge bars (running verically in the picture below) are made from 1 1/4" angle iron.  I got the 1/8" steel sheet for the triangles from Small Parts too. The 3/8" all-metal lock nuts that Berry and Kriege say are indispensible (page 144) on the collimation bolts are really hard to find.  I had to order 50 from The Nutty Company (click on NUTS; see Grade 8 Torque Lock Nuts), but this online store is very good.  The top lock nut was cut in half to minimize its proflile and two layers of EZ Glide pads were used on the corners of the triangles to be certain that the mirror would clear the metal nut.

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This view is from the bottom of the mirror box.   Notice that the front of the box (on the grass) is beveled as Kriege and Berry recommend in figure 7.7 of their book. This important modification allows the mirror box to be lower in the rocker box causing a lowered center of gravity.   My bevel is a straight cut as opposed to their curved recommendation. The advantage of the straight cut is that I then was able to reinforce the box with 1/4" ply on the straight edge. A circle cut from Kydex with drops of Liquid  Nails holds the steel triangles of the cell in  place. The nylon belt used for the mirror sling was from  a suitcase strap from Magellen's.          Click for a schematic of the tailgate (mirror cell)

A black baffle out of 1/4" Baltic  birch (to the right of the mirror box)  velcros onto the gussets in the mirror box (see below).  It  has a 13"  hole cut in the center and rests 9"  below the top of the box and 3" above the mirror.  It blocks light reflecting from the ground up through the tube.    It also provides a platform for the upper tube assembly to rest on during scope  transport.  Additionally, the round mirror cover seen here velcros onto the baffle to provide a dust cover for the mirror.

The baffle in place.

The mirror cover velcroes to the baffle.

The altitude bearings are of 3/4"-thick  medium density fiber board as    recommended by Ray Cash. It is strong and won't warp, but it is brittle, so avoid sharp blows. The method of cutting circles  recommended by Kriege and Berry (figures 6.6 and 6.7) worked really well for the altitude bearings, the arcs in the rocker box, the upper tube assembly rings, and the baffle and dust cover.    The bearings attach to the mirror box by three 1/4" bolts that go  through holes in the mirror box and fasten into brass threaded inserts in the bearings.  The aluminum kitchen drawer handles bolt on too.

The 3/4" aluminum truss poles attach to the mirror box in a manner similar to that described by Ray Cash.  Thus, steel threaded inserts (10-24) are in the mirror box and the bolts go through holes in the aluminum poles (using washers inside and out) to attach them.  This approach (as pointed out by Ray Cash) is not very convenient.  The poles flop about during assembly (though the more I do it, the easier and less Keystone Kops-like it seems).  The problem is that there is very little room in the box (since the UTA has to fit in here during transport).  There probably are better solutions, but this approach generates a very rigid telescope that functions well.  It is just that your friends will laugh as you set up the scope (but you can laugh back from Australia).

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