Ness and I are getting red-giant ages from APOGEE spectroscopy using The Cannon and a training set from Kepler. We worked on making plots that would help us understand where this age information is coming from. Options include: Chromospheric activity (which decreases with time in stars as the magnetic field decays), dredge-up of C, N, O from the nucleosynthetic core (which pollutes the surface abundances over time), trace element abundances (which might indicate birth place and time beyond the information in gross indicators like metallicity and alpha-enhancement), and non-LTE effects (which might be different in different stars since convection patterns and scale are a function of mass).
Tom Herbst (MPIA) showed me his fish-eye all-sky camera and data acquisition system, and we discussed science projects for it with Markus Pössel (MPIA). The whole system is on the roof, so its computer and controller and everything are isolated from all the building systems to protect the building and its IT infrastructure from lightning strikes!
Rix and I asked Yuan-Sen Ting (Harvard) to compute derivatives with respect to elements for the stellar models being used to analyze the APOGEE data. The idea is that we want to ask how well we can linearize the models around fiducial points and then model (and therefore make measurements from) the spectra.