Polarization (BIAS): First measure its background noise before the CCD is turned on (0 seconds).
Dark: The heat electron generated by the CCD itself is small, usually 1 ~ 2 / sec, can be ignored. The required exposure time is the same as the actual observation time.
Pingping: First illuminate the CCD with a homogeneous monochromatic light to derive the ratio of the electron with each part of the CCD, and then divide the actual data measured in this ratio.
Wavelength calibration: illuminate the CCD with a few beam known wavelengths, as a ruler to correct the waveform.
Zhongtian: The celestial body is just through the moment of the midday in its Sunday.
SEEING: It is used for the unstable atmosphere of the earth, and there is always a weak hot air flow above the telescope, so that the star is always flashing and boiling under high magnification. This flicker has a fierce level called the atmosphere.
