# Are astronomers still using photomultiplier tubes for optical photometry?

A logarithmic magnitude scale might tend to show just how deep but noting that the minimum is dimmer than -21.5 mag and probably lasts only a tiny fraction of the orbital period (i.e. a few seconds) makes a good measurement of the minimum quite a challenge.

It seems to me like this might be a situation where a photomultiplier tube and photon counting might be competitive with photometry based on CCD imaging and clever readout schemes.