Quote:
Originally Posted by Drac0
Easiest way is to put the OAG in the image train & set the imaging camera to the correct back focus distance and check it can focus correctly. Then measure the distance from the prism in the OAG to the imaging camera sensor - this is the approximate distance the sensor of the guide camera also needs to be from the OAG prism. Add/remove/change extenders as required to get the correct distance for the guide camera. I find it easier to have the OAG closer to the telescope than the imaging camera - put the camera too close & you may not have enough distance for the guide camera to achieve focus.
Cheers,
Mark
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The easiest way to set up an OAG in my experience is to do it during the day. Get your gear out, focus your OTA on a (very) distant target such that it's focus position is going to be largely similar to focusing on stars. When the main camera is in focus, start moving the guide body in and out of the OAG slowly until you can see focus starting to come together. Then fine tune it. Once that is done, leave it in place, do not disassemble it after each session.
For my OAG the guide camera basically needs to be pushed as far down as it will possibly go to reach focus.