HARVARD SMITHSONIAN CTR ASTROPHYS,WHIPPLE OBSERV,AMADO,AZ 85645
; ECOLE POLYTECH,LPNHE,F-91128 PALAISEAU,FRANCE
; INST HIGH ENERGY PHYS,BEIJING 100039,PEOPLES R CHINA
Cerenkov ring images from single muons have been used to calibrate the Whipple Observatory 10 m imaging telescope. This approach tests the total throughput of the telescope and uses a known atmospheric Cerenkov light signal that closely matches the spectrum of the atmospheric Cerenkov signal from an air-shower, The absolute calibration is derived by matching the observed ring images with those predicted by a simple geometrical and physical model; a value of 1.25 +/- 0.13 photoelectrons equivalent to 1 digital count was found. Using this value simulations indicate that the telescope had an energy threshold of 300 GeV when this calibration was made.