(a) estimated wavefront of the nominal SCExAO system during on-sky observations and reconstructed by combining the estimated modal coefficients of the 30 Zernike modes. The estimated WFE is ∼187 nm rms. (b) introduced, (c) estimated, and (d) residual wavefront from closed-loop tests during on-sky observations. (b) introduced wavefront, consisting of 30 Zernike modes, with an rms WFE of ∼146 nm. (c) estimated wavefront, using the same 30 Zernike modes, with an rms WFE of ∼244 nm. (d) residual wavefront (introduced minus estimated and nominal wavefronts); the rms WFE is ∼78 nm.