Hi Greg
The QE for my camera for Ha is about 40% so its getting on the low side. But I do live in a low bortal 4 upper 3 area. I have tried to image just Ha areas and it failed to pick up anything. The camera is good a bright DSO objects but fails at the dim ones.
I have attached the QE for you to look out.
QE Curve
We suppose the QE peak value is more than 50%.
https://astronomy-imaging-camera.com.../ASI071-QE.jpg