instrument epochs

In another not-much-research-day, I did get in an interesting call with Megan Bedell (Flatiron) and Lily Zhao (Yale) about our project to precisely calibrate the EXPRES spectrograph. Zhao is using our dimensionality reduction to look at instrument changes. She can use it to split the months of instrument use into sensible (what we call) epochs. Each of these epochs has a wavelength calibration with a sensible, low-dimensional representation. So the value of the dimensionality reduction is not just to make the calibration hierarchical, but also to find change points and—more generally—put eyes on the data.