The Directly Measured Optical Background and the Unexplained Remainder: A Budget with Its Errors Carried Through

This paper addresses a specific question in the accounting of the cosmic optical and infrared backgrounds: how large is the difference between the directly measured cosmic optical background and the sum of counted galaxies and known foregrounds, once the uncertainties of every term are propagated honestly? The approach is a transparent computation from stated inputs drawn from the published literature, carried through in a deposited script whose output supplies every number quoted here. The principal computed values are: measured cob nW = 16.4; integrated galaxy light nW = 8.31; foregrounds nW = 2.5; residual nW = 5.56; residual error nW = 1.78; residual significance sigma = 3.13; residual frac of measured = 0.34; igl frac of measured = 0.508. These are compared with published measurements and budgets at the same wavelengths, and the agreement or disagreement is stated in each case. The study is computed from stated assumptions, not a new measurement; its contribution is arithmetic that can be checked line by line, with sensitivities reported wherever an input is uncertain.