Yes, I am not sure how to do a darkframe. Do you know what settings I should put on the camera to make one? I could add it to the script for next time.
You can set canon darkframe subtraction auto, off or on using set_nr (0,1,2 respectively). Note that this will take a darkframe after each exposure, doubling the time required to capture each image, and halving your actual coverage of the sky.
You could also take a darkframe manually (by covering the lens) and subtract it in post processing. You'll probably want to work in raw or DNG if you do this.