The CAMEX-4 Dual-Beam UV-Absorption Ozone Photometer dataset was measured by using a photometer consisting of a mercury lamp, two sample chambers that could be peridically scrubbed of ozone, and two detectors that measured the 254-nm radiation transmitted through the chamber from the lamp. The ozone number density was calculated using the ozone absorption cross-section at 254nm and the Beer-Lambert Law. The one second data collection rate at the minimum detectable concentration of ozone (one sigma) was 1.5 x 1010 molecules/cm3.