Haven't read all of the paper yet but as for the technical details for those who are interested. It was conducted in 2009 from ESO La Sillia observatory. An SBIG STL-11000M was used with a Canon EF 50mm F/1.4 USM & Canon EF 200mm F/2.8L USM, and Baader LRGB filters.
300s L exposures were used with the 200mm and 600s with the 50mm. Some of the deeper areas that they were imaging had a flux of 28 mag/arcsec^2 so pretty dim
That was with the 50mm, they reached approx 27 mag/arcsec^2 with the 200mm which is comparable to the depth of the 2MASS project.
Planning on making my way through the paper as the day progresses
