celestron wedge mod to stop racking

I was having problems pointing the telescope. I traced it down to the fact that the Celestron Heavy Duty Wedge isn't really very heavy duty. The problem stems from the fact that the two side plates are held in place with four smallish screws that under loading sideways will allow the wedge to rack. I measured this with a dial indicator and got a reading of .005" side motion measured from the base of the pier mounting plate to the top of the side plate near the screw. Now that may not sound like much but extrapolated at the top of the Declination axis it works out to almost a millimeter (.040") shift. The fix is presented below.

back view

The inside of the wedge is essentially a rectangular open box bolted together at the top and bottom. When the scope is pointed to the extreme East or West, the cantilever loading of the telescope corrector assembly, counterweights and mounting rails bends the screws allowing the wedge to rack sideways. The screws are small, counterbored into the side plates and without washers to spread the load.

angle view

I attached a piece of aluminum angle to each side arm bolted on using the slot in the Dec arm and positioned flush with the front face of the arm. The thing you have to watch out for here is not restricting the motion of the Dec adjustment. I'm sort of close to doing just that but I already had my polar alignment pretty close.

The Plate

Across the face of the angles I attached a sheet of 1/8" thick aluminum that is notched to clear the Dec adjustment assembly. The important thing is not the material thickness but it's height. The aluminum sheet closes off the end of the box. The wedge will try to buckle the plate and that's the motion it needs to resist. As you can see it's held in place with numerous pop rivets. It ain't pretty but it has worked well enough.