Читать книгу The Doppler Method for the Detection of Exoplanets - Professor Artie Hatzes - Страница 34

An important characteristic of a CCD is its linearity in response to the incident light. The observed count should be linearly proportional to the intensity of the light—expose for twice as long and you should get detect twice as many photons.

Most modern CCD detectors generally have excellent linearity (Figure 2.18). The linearity of a CCD is trivial to check. Observe a white-light source at different exposure levels and plot the total counts (minus the bias level!) as a function of exposure time. If one sees a deviation from a linear behavior (red dashed line in Figure 2.18), then one should avoid exposure times which produce counts above this level. For Figure 2.18 where we have marked a hypothetical nonlinearity with a red line, this is at approximately 170,000 ADUs.

Figure 2.18. The CCD linearity as indicated by the number of detected photons as a function of the exposure time. The red dashed line shown would indicate a strong non-linearity at high count rates.