Camera for OAG with long focal length scope

[David at Bythel Obs]

I have an edge 11 with celestron OAG but cannot get asiair plus to calibrate as cannot find stars. Pls help what camera do I need. I am keen to take subs even at f10 ie 2800mm fl. I have achieved using 250mm  fl guidescope  with 300s subs guiding at 0.4”rms but need to use OAG for space reasons as I am in a dome. Any thoughts most welcome

[newbie alert]

I use a 290m with a oag with my c8.. plenty sensitive enough, never had an issue with finding guidestars 

What camera are you using?

And what oag?

Edited February 20, 2023 by newbie alert
Added info

[David at Bythel Obs]

Thanks for your rapid response I have tried a Zwo 178 and 120mm using the celestron OAG but can’t find stars seems to use a bright pixel!!

[ONIKKINEN]

9 minutes ago, David at Bythel Obs said:

Thanks for your rapid response I have tried a Zwo 178 and 120mm using the celestron OAG but can’t find stars seems to use a bright pixel!!

You need a proper dark library and a bad pixel map, PHD2 should guide you through that. On top of that you need to set the minimum HFD value to something larger than a hot pixel but smaller than an actual star. What that value is depends on a number of things but if you have it set to 1 pixel increase it right away.

* and bin the camera to something reasonable. 1x with either camera is far too high a resolution.

Edited February 20, 2023 by ONIKKINEN

[vlaiv]

Do you have your OAG properly focused?

If you are out of focus - you won't see any stars.

You can try very long guide exposure (do a half a minute exposure with OAG camera) - just to see if you can spot very faint doughnuts - those are out of focus stars

[newbie alert]

As vlaiv has suggested , with a oag you need it set up correctly.. spacing needs to be correct to the imaging sensor, and dimensions from the prism to the imaging cam and the prism to the guide cam the same.. taking note the backfocus distance between cameras won't be the same..

I have the long side if the guide cam parallel to the long side of the imaging cam 

Then there's the prism depth, ideally take some flats to make sure it's not impeding into the light cone of the imaging cam..

I use 3 sec guide exposures , plenty long enough

And make sure the focal length is entered correctly within phd

[Elp]

Which OAG is it, the newer one or older one? I have the old radial guider and finding stars is very easy with that one. Would try as recommended above, your fov with the oag is extremely limited so doing a very long exposure just to see if you're near helps, if you can rotate the prism around the imaging axis that may also help. Else set it up during the day as it's much easier by focusing on a far off object.

[David at Bythel Obs]

Managed to get out last night and achieved guiding with the OAG using my Zwo120mm with the edge at f10 2800mm. Thanks for all comments and advice getting focus was the real issue although getting the calibration settings right were also a must . Photo m81 15x300sec subs. Stars look pretty good.

[wavydavy]

My C11 HD I used a lodestar X2, With OAG through a starlight xpress filter wheel. Worked fine. Having said that, I also used the focal reducer bringing it down to f7, at F10 it must be v hard to get focus etc when the seeing isn't to great..........