Sorry David, I thought you were aware of the site:
http://translate.google.com/translat...%3Den%26sa%3DG
Go to: Forum - testing of optics - optical directory reports(top of page)
In the image below, the top star test is without a prism - note the greater red fringe inside focus. The bottom star test is with a prism and the colors are brought closer together:
http://rohr.aiax.de/CelED80JK-02.jpg
In the next image, note the change in strehl ratios for the different colors - this test is done without changing focus. When focus is changed to suit each color the strhl ratio is high for all colors for the ed80:
http://rohr.aiax.de/CelED80JK-04.jpg
Note: the above is my interpretation of the article - I'm no expert.