With practice, you will easily be able to do this before the CCD finishes reading out in 2x2 binning.
== Dome flats ==
If poor weather conditions during twilight prevent you from obtaining sky flats, dome flats can be used instead. These can be obtained at any time by imaging a "uniformly" illuminated screen in the dome in the following way:
# Follow the [[#Start-up recipe|facility start-up procedure]] but '''do not open the dome'''. '''Remember to open the mirror covers.'''
# Follow the appropriate [[#Instrument start-up procedure|'''instrument setup''']] procedure.
# '''Switch on the domeflat lamp''' by turning the dial on the wall between the North pier and the blue console.
# '''Rotate the dome''' to an azimuth of 180°, such that the lamp on the catwalk illuminates the round, white screen on the dome as uniformly as possible.
# '''Slew the telescope''' to HA = -3h 16m, Dec = -14° 37'
# '''Expose and save''' at least fifteen flats for each of the required combinations of filters and binning.
You may need to adjust the dial on the incandescent lamp between filters to achieve manageable exposure times. With STE3/4, keep exposure times ≥1s to allow the shutter time to open and close.
== Observing recipes: on sky ==
