We once did a video on the Harz, but never put it on DVD. My brother shot the footage. There was on location that had a simultaneous departure on the schedule, but I cannot remember the station. You could go around the bend and see an s-curve beyond the depot and be roughly where the lines split. Made for some cool shots. Maybe someone else here can fill in the station name. Look at the timetable and maybe you can figure out the busiest places/lines to get the most bang for your buck. There is probably a discussion group on German Steam you can do as well. Also see when those articulated engines are running and where.
Its the closest thing to regular service steam left really!!!
Greg