Dobsonian Base

I just finished this base and there is one problem with it that I don't know how to solve. As indicated in the picture it wobbles quite a bit. It stops after a while and I don't know how much this is going to bother me when I'm out observing but I figured I'd ask the experts for some help. Thanks for your ideas in advance.

Rick Riley

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Looks like you don't have enough support in the rear. The problem is often difficult to solve because of the space needed for the OTA to swing through. I see that you've attached the sides to the side of the baseboard of the rocker box. It's better to make the base wider and rest the sides on it. However, you can salvage the status quo by gluing in some, say, 3/4" x 3/4" square dowel or such (plywood scraps can also work) along the inside seams in the rocker box. I use Titebond II wood glue--great stuff. If it won't interfere with your tube, also consider gluing in some wood triangles to stiffen the connection between the sides and the bottom in back.

Once the sides are firmly secured by a glue bond using the square dowel, the only way the sides can wobble is through flexure. To limit this further, I suggest building eyepiece holders. You just take a board and drill 1.25" and or 2" holes at regular intervals and attach it with some framing to the sides. That should stiffen the sides up a bit.

The final thing is that you may get some flexure in your ground board. You've got a nice wide footprint there, but there must be considerable distance between where the rocker box is supported on the ground board and where the ground board is supported by the ground. We usually like to stack these weight bearing points as much as possible, but if the resulting stance is too narrow, some separation, possibly with reinforcement of some kind, is required. Anyway, watch for flexure there and reinforce the ground board if necessary.
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Mike