This piggyback attachment was designed for AP400 counterweight shaft. Weight of the DSLR camera is used to balance the telescope, hence less counterweight is needed (as oposed to traditional piggyback with DSLR on top of the telescope).

Piggyback attachment body is made from few scrap pieces of 12mm plywood. The triangles visible serve both to brace the camera plate and they also lock the attachment on the shaft. There are 2 camera plates, only one is used for now. I have used Bogen/Manfrotto quick release plate, which is attached to a small plywood circle. Two pieces of plastic are located between the circle and the attachment body to prevent "sticking" of these surfaces. Camera orientation is locked with a specially made plywood nut (this small sticks allow better grip).

This attachment allows DSLR to be oriented completely independently of the main scope.

I have tested this setup with lenses up to 100mm. No slippage was visible on 10min DSLR images, and - more importantly - no vibrations were noticed at the telescope. For larger lenses, I would recommend to use "side by side" plate as featured on another page here.

It proved to be a nice accessory, allowing duplication of the available targets for photography at no much additional weight in the field.

I was able to control all cameras (main camera, guider camera, DSLR), mount, Robofocus from one laptop in the field!

Few caveats
1. Despite the independent regulation, no sky orientations are accessible to DSLR for a particular scope orientation.
2. Cables need to be routed carefully to avoid catching and snags.
3. One needs to synchronize DSLR imaging with CCD imaging - one may need to wait for DSLR exposure to end before slewing to a new target, one would not disturb the setup changing for new DSLR target while CCD exposure is taken etc.