We are left with the background, read-electronic, and confusion noise components. So all we need to know are the backgrounds, read noise and instrument gain. For 2MASS, the read noise is between 40 and 60 electrons. The following plots show the predicted noise compared with measured coadd background and noise. The plot is given below.
Extinction is the culpret.
Trends that seem to be out of line with the bulk trend are due to time-varient changes in the noise characteristics. The derived confusion noise is straight forward, so there is not much room for major blunders here. The data are telling us that the confusion is small for densites up to 3.5. In order to apply these methods to the database, it is necessary to characterize this ratio in functional form. A quadratic polynomial satisfactorily fits the density range between 2.4 and 3.4.