off axis guider advice

[muletopia]

Hello,
I would appreciate advice on a suitable off axis guider and camera to suite a Tak Mewlon 250..
The main camera is a QHY 8l, I have a ZWO ASI 120mm I could use as a guide camera
but better alternatives are available, perhaps a ccd guide camera with its ability to guide on fainter stars.
The offers out there baffle me.
Chris

[JohnA]

Hello Chris

On my C9i am using the celestron OAG due to its large prism and the ASI174mm mini guide camera. Works a treat and takes advantage of the big prism.

This seemed to be the advice always given for scopes of that focal length.

I also have the 120mm but use it on my small SVBONY SV555 scope and that always finds guiding stars without an issue, but i have not tried it with the OAG, and not sure i will bother to be perfectly honest.

Reason i went with the celestron over something like the ZWO OAG-L and some of the others was that it can be screwed onto cameras rather then bolted on, and you can rotate the main camera or the guide camera individually. With something like the ZWO OAG-L you would need to also add a rotator.

The disadvantage of the celestron OAG is its size, its 29mm thick, so if backspacing is tight, it may not work for you

[muletopia]

Thanks John, the individual rotations do sound attractive and I have the back focus range to attach it. Joshua Bunn made an adapter to attach my qhy camera to the 42 mm female thread the scope supplies, I guess I would need one for the OAG.
A couple of months ago there was listed a CCD guide camera which might do the job. The add timed out in the imaging equipment forum and I can find no track of it now.
Chris

[gregbradley]

I don't think there is any ccd guider more sensitive than a cmos one.
I use a zwo 190 and i think a 120.

Almost never can't find a guide star.

Greg

[Paul Haese]

At Swan Reach Imaging, we have in the past used a ZWO OAG-L on a Mewlon 250 CR. Worked well with a 190 Mini guider. Always plenty of stars to be found.

[toc]

I would recommend the ZWO ASI174MM Mini - has a really big chip, so make it a lot easier to find stars.

[muletopia]

Thanks JohhHello Chris

On my C9i am using the celestron OAG due to its large prism and the ASI174mm mini guide camera. Works a treat and takes advantage of the big prism.

This seemed to be the advice always given for scopes of that focal length.

I also have the 120mm but use it on my small SVBONY SV555 scope and that always finds guiding stars without an issue, but i have not tried it with the OAG, and not sure i will bother to be perfectly honest.

Reason i went with the celestron over something like the ZWO OAG-L and some of the others was that it can be screwed onto cameras rather then bolted on, and you can rotate the main camera or the guide camera individually. With something like the ZWO OAG-L you would need to also add a rotator.

The disadvantage of the celestron OAG is its size, its 29mm thick, so if backspacing is tight, it may not work for you

On my C9i am using the celestron OAG due to its large prism and the ASI174mm mini guide camera. Works a treat and takes advantage of the big prism.

This seemed to be the advice always given for scopes of that focal length.

I also have the 120mm but use it on my small SVBONY SV555 scope and that always finds guiding stars without an issue, but i have not tried it with the OAG, and not sure i will bother to be perfectly honest.

Reason i went with the celestron over something like the ZWO OAG-L and some of the others was that it can be screwed onto cameras rather then bolted on, and you can rotate the main camera or the guide camera individually. With something like the ZWO OAG-L you would need to also add a rotator.

The disadvantage of the celestron OAG is its size, its 29mm thick, so if backspacing is tight, it may not work for you oag and camera, celestron and the 174
Chris

[muletopia]

Thanks for all the advice. I have ordered the celestron oag and zwo 174 mini, lured by John's description.
Chris