The Effects of erenkov Light Pulses on a Stellar Intensity Interferometer

Abstract

Observations of Čerenkov light pulses due to cosmic rays have been made using the large reflectors of the stellar intensity interferometer at Narrabri Observatory. The rate of arrival of correlated pulses in the two reflectors has been measured as a function of the pulse height, zenith angle, separation and relative alignment of the two reflectors. The results are used to calculate the unwanted correlation due to Čerenkov light in the interferometer at Narrabri, and it is found to be negligibly small compared with the correlation due to the faintest stars in the programme. It is shown that a more serious limit to the sensitivity of the interferometer is set by the general background light from the night sky, and it is pointed out that this conclusion applies generally to larger and more sensitive instruments.