Finally made some more progress on this project. The order of play is to get a conventional off axis guider system working (leaving space for the fast guider plate) and get it mounted and working on th telescope with my Coma Corrector and Artemis 285 using a webcam to guide. The deflector plate and mechanics will be added in once the first stage is proved to work.

I've made up a webcam with SC long exposure and a black and white ICX098 chip. This camera has a 1.25" nosepiece. THe sensor is quite close to the front of the sensor. No active cooling, but the case acts as a nice heatsink. Bringing the sensor near the front of the nosepiece allows more flexibility on mounting the off axis guider.

I've made up a part which screws into my Artemis camera, and consists of a wide (2.5 inch plus) chamber for the deflector plate, and a slot to mount the OAG prism behind the deflector plate. The MPCC correctly held 37-38mm in front of the camera body (55mm ish from the sensor). Immediately in front of the camera is a mounting for a 1.25" filter. This means I can use narrowband filters without effecting guidestar brightness.

Before attempting to incorporate the fast guider deflector plate I decided to perform some telescope tests. I want to prove that the systemed worked as a conventional OAG - sending corrections to the mount via guidedog. Essentially just replacing my separate guidescope. The main target was to prove I can get the imaging and guidecameras focused, and that I can find guidestars with reasonable hassle.

Sitting outside now, finally got the damn thing focused together with the guide camera... and reeling off 20 minute exposures quite happily.

The major advantage of using an Off Axis guider is the massive reduction in differential flexure between the guidescope and the imaging scope. This is strongly reduced with Off Axis guiding.

People complain about off axis guiding because it can be more difficult to locate good guidestars with the limited field of view of an off axis guider. Well, sitting on my guidedog screen are 10 stars to choose from, and that is without any adjustment.

off axis guider test