I had a short phone call this morning with Jeffrey Mei (NYUAD) about his project to find the absorption lines associated with high-latitude, low-amplitude extinction. The plan is to do regression of A and F-star spectra against labels (in this case, H-delta EW as a temperature indicator and SFD extinction), just like the project with Melissa Ness (MPIA) (where the features are stellar parameters instead). Mei and I got waylaid by the SDSS calibration system, but now we are working on the raw data, and continuum-normalizing before we regress. This gets rid of almost all our calibration issues. The remaining problem (which I don't know how to solve) is the redshift or rest-frame problem: We want to work on the spectra in the rest frame of the ISM, which we don't know!