The SBS SM-3 Seeing Monitor is essentially identical to the former SM-2 but with a new enclosure. Like the SM-2 it is based on a QHY high QE, low noise, CMOS sensor, a high quality 100mm f/3.5 lens and custom seeing monitor software written by Dr. Alan Holmes. The SM-3 Seeing Monitor constantly monitors the seeing for any 12 hour period and displays the measurement on the computer monitor, logging the data to a text file for later analysis.