MAX-DOAS is a technique that can be used to measure pollutant concentrations and vertical profiles in the atmosphere via remote sensing of sky-scattered light with a telescope. Measuring SO₂ is particularly challenging because of low light intensities in regions where SO₂ absorbs solar radiation. Here, we performed experiments that document inaccuracies in these measurements as a function of spectral fitting windows. We provide recommendations for measuring SO₂ with greater accuracy.