In-camera intervalometer, stacking and processing. I believe that Canon's R&D engineers are also amateur Astronomers.

Star trails are not only cool, but they show you the declination lines on the Celestial Sphere!
How far South can you see? If you reside in the Northern Hemisphere, take your latitude and subtract 90. That is the declination of your Southern horizon. It's that simple! (if you live in the Southern Hemisphere you can see all the way to the Celestial South Pole! But you can easily calculate how far North you can see ?).
Of course, add 10° for easy viewing.
(From my 9°N latitude, I can comfortable see objects that are as far South as -71°)