Astronomical photometry like other scientific methods is always forced to search for up-to-the-minute instruments and the most sophisticated devices. The photomultiplier tube (PMT) is the most widely used photon detector offering high sensitivity and gain with acceptable quantum efficiency and spectral range but it also has some disadvantages. During the past few decades all of these parameters have been improved and it seems likely that possibilities for their continued development are exhausted.

In the meantime, technical development — especially micro electronics and semiconductor technology — has produced a new detector, the avalanche photodiode (APD). The APD which is often referred to as a solid-state PMT is just at the start of its career and we may expect its rapid perfection. Although properties of APDs were first discussed almost twenty years ago their mass production did not start until 1990. Early silicon APDs had very limited dimensions compared to PMTs but unfortunately this also implied that their photosensitive area was less than 0.25 mm. One more year of development has been enough to increase the photon collecting surface by a factor of 1000 and APDs may soon become possible rivals of PMTs.

Following a brief description of the new device and discussion of its operation a comparison of photodetector performance will be given in order to draw attention to those parameters which are of great promise. Those sections of astronomical photometry which are ready to benefit from the suggested testing and use of this kind of photon detector will be highlighted.