The Zodiacal Foreground at 1.25 Microns: How Precisely Must It Be Removed to See the Background Behind It

This paper addresses a specific question in the accounting of the cosmic optical and infrared backgrounds: by what factor does foreground zodiacal emission exceed the near-infrared extragalactic background as a function of ecliptic latitude, and what subtraction accuracy does a background measurement therefore require? 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: zodi ecliptic plane nW = 475; zodi pole nW = 62; zodi beta45 nW = 109; ratio plane to ebl = 31.7; ratio pole to ebl = 4.13; residual after 1pct subtraction pole nW = 0.62; residual after 1pct subtraction plane nW = 4.75; residual frac of ebl pole = 0.0413. 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.