Manual barndoor tracking with long focal length lenses can be done but the exposures must be short and some will be discarded. The next 3 photographs were all taken with stacks of short 15 second exposures.

September 3, 2010
Astrohutech modified Canon 50D with Canon 100mm macro lens, f/2.8
ISO 1600, 2 x 15s using manual barndoor tracking
Processed with ImagesPlus v3.80, CS4, ACR, Neat Image