I found a better method for using ImagesPlus, RegiStar and EasyHDR for doing HDR images and getting the full dynamic range of the target object.
Here is the first image. It is from only HA and O3 narrowband data taken with the Skywatcher 150mm F5. I will explain the method later.
THe horizontal lines are what is called banding pattern and it is inherent in all sensors and is only visible if you stretch very dim images to the limit. I only had one of each 16 min exposure so the banding pattern is not averaged out.
In the past I tried digital development and adjusting levels before putting a set of images into EasyHDR and niether was really satisfactory.
The answer was obvious in hindsight as it was simple. Just put the corrected (for flats etc) linear images from ImagesPlus straight into EasyHDR. Select raw rather than JPG. Of course these images have to be made identical in size and region using RegiStar first. This is done so there is no alignment necessary in easyhdr.
I only adjusted the compression variable in EasyHDR and then only had to adjust levels in PS from the resultant LDR image. No curves!