Knight-Templar (Method 1) Just drag the channel you want to blur to the "Load Channel" icon at the bottom of the channels layer (it's the dotted circle). That should load the channel, then go to the background layer and duplicate it in case you don't like the effect, then select gaussian blur and just the background should be blurred. (Method 2) Another way would be to duplicate the background, then blur it. Then load the channels of all the objects you don't want blurred (ships for e.g.) and delete from the blurred background. That should do it if I am understanding you correctly.