Notes. (1) To measure the electronic offset signal. (2) To center targets in the image (imaging mode), and to focus the telescope. Fast reading with relatively high reading noise. These images are not saved. (3) To take science images. (4) To take flat field images, to correct for the pixel-to-pixel differential response. This has to be done preferentially on the sky (see below) and for each filter, as the response is very different from one filter to the next. (5) To locate the slit x-position on the CCD before moving the telescope to then center the target within the slit. The slit is seen thanks to the sky surface brightness. Rapid reading mode. (6) To move the target at the slit position. Rapid reading mode. Images are not saved. (7) To take the spectrum of the science target (blue or red disperser). In principle to be done without other filters in the beam (but can be done for special reasons), and with an order separation filter for the red disperser. (8) To take wavelength spectral calibrations in order to transform the x-position into wavelength. (9) To take spectral flat fields to correct for the CCD differential pixel-to-pixel response.