A Tale of Two Shelves

While I have a large accessory tray for my CGE mount (now sadly discontinued by Starizona though a 'clone'is being offered by one of the folks in the CGE Yahoo! group) I needed a lot more space to put either my ST-4 auto-guider or my Acer netbook and whatever other flotsam and jetsam accumulates around a mount when imaging. This meant making some form of shelf that would be able to be easily attached to either the tripod legs or the Starizona unit. In the end it took two shelves...

Shelf number one

After several tries at coming up with something simple that would ride on the CGE's tripod I finally gave up and turned my thoughts to the Starizona. Their tray is very heavy (3/8" aluminum) and would any shelf I'd need easily. A 'slip-on' scheme where the new shelf just slid onto the Starizona tray seemed to be the best way to go as it would mean that no holes would have to be drilled into the aluminum.

After much cogitation I settled on a shelf of 1/2" plywood measuring 10" x 20"; quite large enough to hold the Acer netbook and a mobile mouse. It would have an 8" x 1" slot milled into it near the front edge to allow the passage of the ST-4's various cables. The cables passing through the shelf would act as a 'stop' to keep the ST-4 from sliding off should a cable be pulled. The netbook's cables would all pass to the rear to the power source and a USB hub.

The shelf would ride on top of two brackets of 3/4" plywood. The top of each bracket would have a recessed section 1/4" deep where the shelf would ride and each would have a 3/8" slot milled into the rear face to allow the whole unit to slip over the edge of the Starizona tray. Making the brackets 3" deep would give them some strength though the shelf would not take being leaned or sat upon.

Acer netbook and mouse

ST-4 Star Tracker

Not being a cabinet-maker, nor having all of the needed equipment I enlisted the help of Pete, one of the members of our local club who is a woodworker and luthier. He graciously offered to build the shelf to my specificatons. Instead of the inexpensive plywood that I had envisioned Pete built the shelf out of some very nice birch and fashioned the brackets out of some nice 3/4" spruce. All of the edges are rounded over to keep them from chipping and two screws hold each bracket to the shelf. It was finally finished with some clear urethane.

There needs to be something to stop the unit from sliding off of the accessory shelf so I screwed in a few small screw eyelets on the inside of the brackets where they're out of sight. A small bungie attached to these then wraps around the central threaded rod of the CGE's tripod. This serves to hold the unit tight to the Starizona shelf.

Bungie restraint system

Note: If one is making one of these and will be using it to carry an ST-4 Star Tracker then I would perhaps make the shelf 10.5" or 11" deep. The ST-4's camera cable is pretty 'non-bendy' and you want to give it room.

If you don't have a tray-type spreader you can still attach a shelf to your CGE by making a bracket such as the one in the graphic below. It replaces the Starizona accessory shelf and is fashioned from 3/4" plywood. It should extend out from the central threaded rod far enough so that the shelf clears the legs. It can remain in place while the shelf itself is removable. Two 3/4" ply 'spacers' glued to the bracket strengthen the connection. It slips on before the Celestron spreader bar is put in place and is held by a nut and washer that can be tightened down after the spreader bar is tightened.

Shelf number Two

The idea for the second shelf came into being from my always having to place some cardboard on top of the CGE's lower brace to keep my mains-power adapters (and other stuff that isn't needed directly at hand but is neccessary at the mount) out of the dew and mud.

This shelf would be a lot simpler than that described at the top of this page. It would 'ride' on top of the CGE's lower brace bars with only gravity and some 'stops' to hold it in place. 3/8" Finish birch plywood was pressed into service and cut into a 'rounded' triangle. The rounding was done by putting some small brads into the plywood and placing a spline on them and tracing the curve.

To make a curved line first draw out your starting triangle on the piece of wood. This identifies the corners of the rounded triangle. Then place some brads outside the triangle; two off the corners and one off the centre of one of the sides. Now 'clamp' your flexible piece between the three brads and draw the curve you need. Do this three times and you have the rounded triangle shape that is needed.

The stops are just some 1/4 round trim cut a few inches long and glued to the bottom of the shelf. These sit either side of the brace bars and keep the shelf from sliding in any direction. It takes seconds to put in in place and is very light, but strong.

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