Hubble s Hidden Treasures 2012 Image Processing Contest ESA HubbleContestants in this competition had to process previously unpublished images with astronomical image software used by ESA and NASA.
You can process the data in any way you want, and combine them as you wish. The end or intermediate results can be enhanced using any technique. The only thing that is strictly forbidden is to paint on the image. Only tiny cosmetic defects can be painted over, such as cosmic rays, bad pixels, satellite trails, etc.
You may fill gaps between detectors or pointings with data from ground-based telescopes, providing you clearly state what data you have used. You must not simply clone or copy to fill these.