The longest photographic exposures in history

[massimo]

http://itchyi.squarespace.com/thelatest/2010/7/20/the-longest-photographic-exposures-in-history.html

[Dave R]

That's cool. I wonder how you compensate for reciprocity failure.

[massimo]

Found something about the tecnique.
http://www.tentimesone.com/the-art-of-ultra-long-exposure-photography/