This statement about the magnitude dependence when modelling objects seems a little subjective, and perhaps unnecessary.  I think there would be occasions were it would be important to take the increased variance of high flux pixels into account: PSF modelling  from space, for example.  (Even as it stands I think the sentence ought to end `...since the best-fitting model becomes magnitude-dependent.`)

So I guess I suggest replacing the sentence `Including the Poisson... magnitude-dependent.` with something like `We do not include the Poisson noise due to flux in the objects themselves as the sky dominates; this could be included if desired, for high-object flux or low-sky level simulations, for example.`