Trouble guiding with 290MM Mini

matthewhumphrey

I am trying to use the OAG-L with the ASI290MM Mini, and so far have not had success. I am using the ASIAir Plus.

I'm not sure if my problem is focus, light pollution or something else. I am able to get an image on the Guide Page of the AAP App, but I wouldn't say the stars are "sharp". They look like round fuzzy blobs. But I definitely have a point where if I move the focuser in or out, it gets worse in either direction. (for example, they go from fuzzy blobs to donuts).
I'm not totally clear on what the image should be for OAG guiding, or what the limitations are with noise pollution (i'm in a bright class 5-6 area). But i have the telescope trained on a very bright star.

When I get the focus as good as I can, I click the calibration button. It says "Calibrating" for about 2 seconds, then goes back to "Looping".

I'm also not clear on the setup for this camera. I'm using a Celestron C11, and have an M48/2" nosepiece attached to the OAG-L that goes into the rear cell of the telescope. It seems like the best results I can get are with the 22mm extension tube removed. But I thought the distance from the prism to the guide camera sensor needs to be 55mm. With the 22mm extension removed, it seems way too short. However, with the extension on, I can't see any stars at all.

Any advice is appreciated

Improve101

matthewhumphrey I was thrown off by this also initially. With an OAG the star shapes are more like crescents, and that is ok.

Also, it's not from the prism, the distance is the same as your main camera sensor, so you still have to count the distance before the prism as well as after.