Residuals for a light-curve model including refraction fitted with a plain transit model without refraction for Jupiter. The dash-dotted red line is for a plain model with identical parameters as for the refraction light curve. The dashed green line is for a plain model with fixed, correct limb-darkening coefficients (LDCs). The solid blue line is a plain model fitted with 10% freedom in the LDCs. The vertical black lines mark when the planet limb and centre cross the star limb. The reference time is set to mid-transit.