Today was the first day of the meeting The Galactic Renaissance, a meeting in honor of Judy Cohen (Caltech), who was one of my (three) PhD advisors (with Blandford and Neugebauer). On the plane to the meeting I built a brand-new talk about data-driven models of stars, bringing in stuff we are doing in HARPS and Gaia and connecting it to what we are doing with The Cannon.
One highlight of the meeting was Steve Shechtman (OCIW) talking about a new infrared multi-object spectrograph he is designing for Magellan. He talked about some interesting instrument design considerations, which was fitting, because Judy Cohen built (with Bev Oke and a great team) the most highly used instrument on the Keck Telescopes (the LRIS spectrograph, which I used in my PhD work). One point is that all spectrographs are fundamentally trade-offs between spatial and spectral extent, because the total number of pixels is limited. He noted that the spectrograph cost and weight is a strong function of the diameter of the collimated beam, which is simultaneously obvious and non-trivial. Finally, he noted that putting an imaging mode into a multi-object spectrograph substantially increases the cost and complexity: It requires that there not be chromatic optics, which imagers hate but spectrographs don't mind at all!
Another highlight was a talk about Solar twins by Jorge Melendez (São Paulo). By using carefully chosen twins, he can measure abundances better than 0.01 dex. He showed some great data. But even more absurd he is looking at binary stars, both members of which are themselves solar twins! But then if that isn't absurd enough, he also has binary stars, both members of which are themselves solar twins, and one of which has an exoplanet! Awesome. He mentioned that [Y/Mg] is a (possibly complicated) age indicator, which is relevant to things Ruth Angus (Columbia) and I have been thinking about.