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tokens: . This correction therefore also accounts for the average offset induced from the PSF residual ellipticities which is of similar amplitude to the c -terms 15 . We note that we choose not to implement an additional empirical PSF-dependent correction for the PSF contamination, as our α measurements are noisy. Furthermore, if α is not a constant, and is instead correlated with galaxy properties, atmospheric seeing, or image depth, for example, applying an average correction would artificially imprint a PSF-correlation across our full data set that could potentially be more problematic than the low-level average bias that we currently detect. 3.5.2. Accuracy requirements and validation of the first-order systematics model In Fig. 7 we compare two measured star-galaxy cross-correlation functions with the amplitudes predicted by the linear systematics model from Eq. ( 12 ). The standard star-galaxy cross-correlation function, , is related to the linear systematic model parameters as 16 Fig. 7. Comparison of two star-galaxy cross-correlation functions with their corresponding linear systematics model predictions (Eqs. ( 15 ) and ( 16 )) for the five tomographic bins. The star-galaxy cross correlation function (dark blue) is in reasonable agreement with the model (blue bar), where the width of the model reflects the 2 σ uncertainty. The residual star-galaxy cross correlation function (shown pink), and corresponding model (grey), are scaled by a factor of ten in order to display the measurements on the same scale. We also scale the correlation functions by to aid visualisation of the large-scale signal. We can also construct a residual star-galaxy cross correlation function , where As with previous sections, we focus on the ξ + ( θ ) term only, as the ξ − ( θ ) term is consistent with zero for the OmegaCAM PSF. Figure 7 shows reasonable agreement between the measured star-galaxy correlation function (shown dark blue), with the model prediction (blue band, Eq. ( 15 )) which we calculate by taking α from Fig. 6 , β = −1, δ ε PSF from the detector level model in Sect. 3.4 , and the other terms measured directly from KiDS-1000. We note that the band encompasses the 2 σ uncertainty from the measurement of α . All other error terms are sub-dominant. In contrast we find little agreement between the measured residual star-galaxy correlation function (shown pink), with the model prediction (grey dotted line, Eq. ( 16 )). This suggests that our faint magnitude linear extrapolation of the residual PSF ellipticity, δ ε PSF , is not representative of the detector level bias that the galaxies have experienced. We find that the average residual star-galaxy correlation is significantly lower than the expectation from the extrapolated chip-dependent residual PSF ellipticity model. We therefore conclude that whilst we find significant flux dependence in the PSF residual ellipticity for 3/32 OmegaCAM chips (see Fig. 4 ), there is no evidence in the shear catalogue