Thanks for the tip. I was just in the middle of doing that. I think it may have improved it a bit. But I am curious how zero values might affect registration in a masked data set (to ensure clarity, by this I mean values inside of mask remain their value and outside of mask becomes zero). So, If a large part of the image is masked (set to zero), then would the registration algorithm try to align the zeroed part of the data set more so than the actual data of interest?
Also, how does one go about applying the transformation to the pre-masked data?
Thank you for your time and help!