Dichromatic nebula are interstellar gas clouds with intense gravimetric distortions. In 2370, Geordi La Forge ran an analysis on the hull of a Ferengi probe sent by Bok to intercept the USS Enterprise-D. From the analysis, La Forge was able to determine from the particle deposits on the probe that it had it traveled through a dichromic nebula, was exposed to gravimetric distortion, and passed within 1 light year of a class 4 pulsar. With that information in hand, he was able to locate a matching nebula in the Dorias Cluster. (TNG: "Bloodlines" )