Yes, well at 2700mm my idea would not be an option for using the ASI290mm and I can see by where it would frame your shot that it would, in fact, be useless! I had not realised you were using the native focal length of your scope. Chuck a focal reducer on your C14, take your Ha data with the 290 and enlarge it to fit your OSC data in post processing.
There's always a way!
