1. Why improve the sky subtraction?

2. A model fit to the SDSS sky background
2.1. The SDSS imaging data
2.2. Masking the data
2.3. Spline model fit
2.4. Residual tests
2.5. Distribution of DR8 sky subtracted fields and mosaics

3. Mosaicking the SDSS

4. End-to-end tests of the sky background

5. Summary