The comet was almost due west, and in fact passed the due west point within a few minutes of photo, so we need only look for a vantage point to the east. Note that most of the Google images are from a western view, showing the castle in the late afternoon sun.
As luck would have it, Google 3d buildings includes the castle, and everything lines up nicely from the POV of a ridge in the foreground of the Google Earth screen shot below, which includes a line of sight with bearing indicated. So, if this isn't the spot, it ought to be!
I added the zoom-in along the same line of sight which corresponds very well with the APOD. If you are inclined to nitpick, just try it!
Whoa! Wait a sec! It says 80 km. This puts the photographer in the city of Senden, near Ulm ( well known as Einstein's birthplace to Xword afficiandos. ) Google, in its infinite wisdom, chooses not to show the Senden label at this scale. Whaddaya gonna do?
