What is the intent of
fluxMag0Err returned as the second parameter from a call to
A) The Poisson shot noise uncertainty for a magnitude 0 source?
B) The uncertainty in the determination of
“Return the flux, and error in flux, of a zero-magnitude object.”
which implies it’s some shot-noise “extrapolation”
The flux uncertainty of a detection is a function of the photoelectrons in the signal and the noise, but also PSF modeling, aperture corrections, BF effect, etc.
I.e. for a detection that is significantly above sky background but below BF kernel and uncorrected non-linearity the Poisson noise from the photoelectrons attributed to the source is likely very close to the total error. This perhaps applies to 2-3 mag range. Is fluxMag0Err an extrapolation from this region?