A Critical Re-Examination of the Rotation Period of 33 Polyhymnia

While an 18.609 hour rotation period of 33 Polyhymnia had been previously well established, new observations made near opposition suggested a 9.306 hour period should be more fully considered. Additional observations made at large phase angle a month later confirm the longer period of 18.608 ± 0.001 hours, amplitude 0.18 ± 0.02 mag as the most secure result.