Monthly report for June 1999 by Christian A. Hummel: Hummel prepared a six-page manuscript for the Dana Point conference proceedings he had attended in May. Hummel analyzed about 25 nights of NPOI data on the spectroscopic binary Omicron Leonis, and fitted orbital elements and masses to the data combined with the published spectroscopy. He is collaborating with Andy Boden (JPL), Elizabeth and Roger Griffin (UK) on a joint paper. Hummel completed the first version of the raw data reduction program CONSTRICTOR modified for simultaneous six-station observations. He also included the option of saving the raw data into the HDS output file for analysis with the IDL software; however, a bug in the HDS software (Hierarchical Data System, maintained by the STARLINK group in the UK) has surfaced and needs to be addressed in the next month.