Guide camera recommendation?

[Martyn87]

Hi all, 

Now that I have a proper mount on the way, and a camera that I can control from NINA, I'm looking to do some proper imaging when the weather gets better. I'm looking for a camera to use for guiding. This is the setup so far: 

Celestron 6" SCT

F6.3 reducer

Celestron AVX mount

Canon 550D camera

 

I will hopefully have a ZWO OAG-L on the way shortly so I'm looking for an appropriate camera for this, which I think uses a 12x12mm prism? Am I right in thinking that I need to make sure the camera sensor will be filled by the image from the prism? I'm not tied to a particular brand, not needing to stick with ZWO for ASIAIR or anything like that, so I'm open to any suggestions really. 

Thanks! 

[Elp]

A large camera chip will help see stars due to the zoomed in view you'll have from the scope+reducer but it's not essential. The goto mini type zwo version is the 174 mono, but I use a 290 with my C6 when doing reduced imaging fine. An OAG which allows rotation around the central axis helps a lot as you can align it to the long side of your imaging camera sensor (so furthest into the imaging circle as opposed to the short side).

[Martyn87]

Thanks Elp. I hadn't actually considered the rotation. I knew I would need the prism along the long edge of the sensor but hadn't thought much about how I'd achieve it considering I'm not using something like the 2600 and EFW. I guess I have plenty of spare back focus length though, so I'll come up with something. I had thought about getting the Celestron OAG instead, which is rotatable, but I didn't want something that I wouldn't be able to use if I move away from SCTs in the future. 

I'd looked at the 220mm which I think is the successor to the 290? Looks like a nice sensitive camera. I guess mono is the way to go here? 

The 174 looks interesting, Altairs version is actually cheaper than the 220mm. I'm guessing the higher resolution isn't really a lot of help for guiding though, but maybe it could be binned to increase sensitivity? 

[Elp]

Monos the way to go for a guide camera, they can see more stars (and much fainter ones) compared to a colour camera.

People do bin too, you'd need the resolution to support it so a 174 sized camera may do, but note, with an SCT reduced the number of stars on a guide sensor off axis will be small due to the focal length, you may be lucky to get half a dozen at times.

Edited July 13 by Elp