Monthly report for April 2001 by Christian A. Hummel: Hummel reduced several nights of astrometry observations, including the metrology (with help from N. Elias). He added declination and hour angle, which are computed from the siderostat motor angles, as plot variables to aid in the quality assessment of the metrology solutions. Hummel spent one week in Flagstaff helping with the long delay line assembly. Hummel continued the development of his imaging software and completed a modified CLEAN algorithm for wide band observations of composite spectrum binaries.