[Aavso-photometry] UBV Photon Counting

[Arne Henden]

Michael Koppelman wrote:
 > I'm curious about this. PEP is a great thing and complimentary to CCD
 > work and just plain ol' valuable on its own. But your statement implies
 > that there is something intrinsically better about photon counting? We
 > are almost always interested in relative changes in flux so I'm not sure
 > what is so great about photon counting?
 >
photon counting is useful when readnoise is the major noise source,
since it implies nearly zero readnoise (less than 1 electron).
Examples would be low background situations like spectroscopy or
narrow-band filters, or high time resolution such as lunar occultation.
For some instruments, you can actually time-tag every incoming photon
with its time, x and y positions.  For most broad-band applications
that are sky noise dominated, photon counting does not buy much.

Arne