Atik OAG Off Axis Guider

[fatwoul]

I understand what you mean.

The thread of the 16ic tightens to the point the sensor is square to the optical plane for the light coming in*.. i.e. when the screw threads tighten, the camera sensor is aligned to the prism (although there's a circular hole the light comes through - the prism is rectangular).

This means if a star moves along the X axis of the imaging camera sensor (assuming it's aligned by rotation), then the star moves along the X axis of the guide camera...

Yep, that's exactly what I'd like. Unfortunately it looks like the Titan doesn't tighten to arrive at the same orientation.

I'm glad my explanation wasn't as lousy as I thought.

I have two of the extending back focus rings in place for the 16ic that come with the OAG.

I understand why you wish to rotate the guide camera - to align the RA along the X axis and DEC against the Y axis, resulting a better accuracy.

I noticed that in your picture, and I found it interesting. I imagined that the Atik cameras all had their sensors roughly the same distance from their front screw fitting. At least, I was surprised to see that you were using so many of the extension rings, when I am only using the smallest one and a little of the focus extension of the OAG itself. I didn't imagine that the Titan and 16ic (or 314 and 383, for that matter) would differ that much.