BTW, the light Chris uses is the NuArc 40-1KS. These are still out there on the used market. This URL has some info on the product line (which was acquired by a different company): http://www.nuarc.co.kr/1KS_ProductSheet.pdf .
I did not find what the "exposure units" they use are in terms of light quantity, but it's consistent in terms of avoiding warming up and other factors. So, from the practitioner's point of view, it seems to work well, avoiding the multitude of factors that can affect trying to expose via the sun.
Paul