Table 1. These equations describe the best fit linear relationship between naked eye observations (NELM) and the map values of the DMSP and WA (top), and between SQM measurements and the maps (bottom). The estimated uncertainty in the fits are shown in parenthesis. The fits can be used to predict the naked eye star visibility or SQM measured sky radiance in the case of no artificial skyglow (0LP prediction). For the DMSP, the y-intercept represents almost no observed light, while for the WA zero artificial skyglow occurs at x = 2 (the value 25.89 has no physical significance). The large χ2 per degree of freedom in the fits indicates that the fit does not perfectly match the data.
| Data | Skyglow Correlate | Intercept | Slope | 0LP prediction | χ2/dof |
|---|---|---|---|---|---|
| NELM | 2010 DMSP | 5.35 (0.03) | −0.951 (0.016) | 5.35 (0.03) Vmag | 52.7/24 |
| NELM | World Atlas | 6.96 (0.06) | −1.05 (0.02) | 4.86 (0.02) Vmag | 32.4/19 |
| SQM | 2010 DMSP | 21.90 (0.04) | −1.69 (0.02) | 21.90 (0.04) (mag/arcsec2) | 37.7/10 |
| SQM | World Atlas | 25.89 (0.07) | −2.18 (0.03) | 21.53 (0.03) (mag/arcsec2) | 19.9/8 |