I moved some plan files to a USB key because the storage of the ASIAIR is obviously limited. In order to compare my own stacking, and the one of the ASIAIR (which is pretty good for a full automatic process), I have been unable to move back the files from my USB Key to the ASIAIR. Beside this, I tried to remove a dark from a picture already stacked and it's impossible because you can't choose the "stacked" directory as source files for stacking. Except if the goal is to prevent someone to stack with ASIAIR some pictures which have not been taken with an ASIAIR, I think that it should be possible to upload data on the SD card from a USB key. If you are far from home without a PC, It's good to have at least the ASIAIR to stack something.
