Temperature Effects in Photomultipliers and Astronomical Photometry

Temperature coefficients are reported for photomultiplier tube types used in astronomy. For 1% stability of gain and color response, temperature regulation of 1°C or better is generally required. This is nearly an order of magnitude better than what is usually achieved at the telescope, but careful use of a well-designed cold box should make 1°C temperature stability possible. For maximum stability and reproducibility, ordinary blue-sensitive tubes should be avoided at wavelengths longer than 5000 Å, and trialkali cathodes should not be used beyond 6500 Å.