Top: residuals from a greybody fit of the mean dust SED at ν ≥ 353 GHz, using one spectral index. Dashed error bars are the quadratic sum of the statistical error (solid) and the photometric uncertainty. The photometric uncertainty is dominant at ν ≥ 545 GHz and negligible for the lower frequencies. Bottom: residuals from a greybody fit to all data points down to 100 GHz, again using a single spectral index.