Figure \[fig:vignetting\] shows the vignetting present in our system in the form of truncated beam print at the entrance of the camera in the return path. In the absence of vignetting, the beam footprint is expected to be circular. However, due to the small size of the optics, there is vignetting at the edges of the image. Furthermore, the effect is found to be wavelength dependent across the orders and also varies from start to end of each Echelle order. Vignetting causes a change in the centroid of the spectral lines that fall on the detector. The effect is analyzed across the detector and is expected to give a constant outcome as it is a design constraint. However, as shown in Figure \[fig:repeatability\], due to uncertainty in zero-positioning, the landing of the spectra on the detector might vary. Thus the spectral lines that land at different locations on the detector experience a distinct vignetting effects, this results in the errors in centroid estimation of the spectral lines from spectrum to spectrum. To estimate the vignetting from the design; the size of the grating, prism, and the collimator/camera optics have been increased to contain the entire footprint of the beam. The 