On the Expansion of the Orion-Nebula Cluster

Expansion of the Orion Nebula cluster was derived by Strand under an assumption that the scale of the Yerkes 40-inch refractor did not change during a 50-year interval. It is shown that the scale did actually change due to the use of various filters, to readjustments, and to the variable thermal condition of the lens. Consequently, there is now no observational evidence for expansion of the cluster.