We describe the design and performance of a coded aperture spectral imager with a wide spectral range of 320 to 700 nm over 87 channels and 1988-by-1988 pixels of spatial resolution. A custom-designed relay lens was designed and built for the system, including a dispersive prism element in the collimated space of the relay lens. The optical design process, prescription, and performance are reported for the entire system, including calibration and alignment. Simulations of high-resolution spectral images are conducted to verify the reconstruction algorithm and relative resolution of the instrument compared to ground truth data. Measured data were taken with the instrument using both a random coded aperture and standard slit for spatial resolution comparisons. Finally, reconstructed spectral images from the instrument are presented of a sunlight-illuminated flower from 360 to 700 nm.