Hi I have Atik CCD and off access guider....is there any easy way to line-up how far out the off access mirror should protrude into the light path? or is it just keep trying until it shows up in the main ccd.
Set up the scope with OAG and camera and point it at a flat wall, not too brightly lit.
Adjust your camera exposures down until the wall is well exposed but not too blown out.
Then adjust the OAG prism into the light path until you see the prism encroach into the cameras FOV - then back it out again until it's as close to the centre as possible but not blocking any light on the camera sensor.