Which Guide Camera with OAG for 2 scopes

[AndyThilo]

Hi

So I’m swapping imaging train between my GT81 for wide field and my RC for galaxies at both 1624 and 1218 (with 0.75 reducer). 

I want to switch to an OAG to go with my new QHY268C but am not sure whether to get the ASI290 or 174 mini. The latter will be wasted in terms of FOV as the QHY OAG prism is only 8x8 but I don’t have the backfocus for anything else.

Will the 290 be ok at all focal lengths or should bite the bullet and get the 174? Any other options to consider? 

Thanks

Andy

[tooth_dr]

I switched from 120MM to 290MM as an OAG at 1200mm.  Its very sensitive, and have multiple stars to choose from in PHD

[vlaiv]

With that sort of focal length - binning is always an option.

I guide with ASI185mc - color version. It's a bit larger sensor that my OAG can illuminate - but who cares - as long as it works. It has 3.75µm pixel size and I regularly bin it 2x2 (there is option in PHD2) - so my guide resolution ends up being around 1"/px.

Even if I don't bin - I always find guide stars with it, binning just improves SNR.