OAG setup

[KathyNS]

I bought a second-hand OAG, getting set up for galaxy season next spring. It is the ZWO OAG, and it included the matching helical focuser.

After spending a couple of hours with a spreadsheet to work out the spacings, I realized a couple of things:
- If I put the helical focuser on the guide camera port, there is no way to get the 85mm back focus I would need to use the OAG with my focal reducer.
- If I put the helical focuser on the imaging camera side, I can not only get the 85mm back focus, but I can do it with spacers I already have.

So I tried it out today. I set up my C-8 with the OAG, using the adapters from the spreadsheet. I got both paths in focus with the helical focuser set to 4, out of a scale of 0-7. So, the setup works.

I know that conventional wisdom says to put the focuser on the guide camera. But as far as I can tell, what matters is just that the two paths are equal. I just have to remember to focus the guide camera first, with the scope's focuser, and then adjust the imaging camera to match.

Am I missing anything by doing it this way?

[JayTee]

It sounds useable to me. The proof will be in the pudding. Let us know when you make the pudding!