Monthly report for May 1999 by Christian A. Hummel: Hummel added stellar spot parameters to the modeling software, and simulated NPOI observations and imaging of star spots. Hummel attended two conferences, "Working on the Fringe" in Dana Point, from May 23 to 28, and the AAS meeting in Chicago, May 30 to June 4. He gave a talk at the first meeting, and a poster at the second one.