nod-and-shuffle

Yesterday, Bolton and I were able to show that nod-and-shuffle—a spectroscopic mode in which you nod the telescope and simultaneously shuffle the charge in the CCD so as to get perfectly matched on-source and off-source exposures—produces incredibly stable sky spectra. It is truly impressive, because we can average the sky in hundreds of objects and compare, and they are consistent at a level that is yet to be quantified, but thinner than any lines we can plot. Meanwhile, Burles and Cool improved the wavelength calibration and extraction code.