Unable to focus non-mini ASI174MM on OAG

glancey3

I've tried every spacing possible with my Celestron 9.25 SCT and 6.3 reducer, yet I can't seem to focus my ASI174MM as my guide scope on an OAG. My imaging camera is an ASI294 Pro, and I can focus that with the following imaging train (from scope):

Celestron 6.3 reducer + Celestron T-adapter + OAG + filter holder + 11mm + ASI294

But the guide scope on the OAG is way out-of-focus. Does anyone have any suggestions for me to get this fixed?

WalterT

Is it the ZWO OAG or another brand. I’m currently using the zwo oag in a similar train and are able to focus fine. However when I tried the Celestron OAG it was impossible due to their oag’s BF length.

9.25 EdgeHD>.7 FF/FR>Moonlite Focuser >ZWO OAG>11mm ZWO spacers >ZWO Mini EFW>294MM Pro. Using asi290mm mini as the guide camera.

glancey3

I'm using the ZWO OAG. My scope is not an EDGE, however. It's just a 9.25 SCT, with a 6.3 reducer. My camera is the 294MC Pro and instead of the Mini EFW, I'm using the ZWO filter holder, which I believe is comparable to a 21mm spacer in the image train. Also, my focuser is the ZWO EAF, but it is not in the image train.

WalterT

You know what this whole time I’ve been assuming you had a 174mm Mini, but I just re-read you have the regular pancake style one?

Edit: If so, are you using the 10mm extender between the camera and the oag, like this?

glancey3

That’s correct. But according to ZWO, it shouldn’t make any difference. It should be able to focus as a guide scope on the OAG.

WalterT

It makes a big difference in that you don’t have the option to make precision adjustments in/out with the helical focuser. If the distances of guide camera and main camera to the reducer aren’t exactly the same you won’t be able to achieve a good focus. In my case my imaging train is actually 56mm because the T-2 male-to-male adapter in my mini efw adds 1mm of BF so I had to compensate for that in my guider by sliding the top portion of the oag+camera assembly on the oag light tube out a bit. I take it you have also tried that? Also have you tried working out the focus issue during the day by focusing your main camera on a distant target and then adjusting your oag in and out?

glancey3

Well, I found my problem. Stupid is as stupid does. The OAG prism was configured backwards, with the flat side towards the camera. Now I can at least got things focused.

Thanks for your assistance.

WalterT

lol, hey any time we solve a major hurdle like this easily and for FREE it’s a win. Have fun!