2000PASP..112..801K

A spectroscopic imager was designed and constructed to provide a new capability for measuring the spectrum of the sky across wide fields of view. The instrument uses a high-speed optical system to form an image on the entrance slit of a matching stigmatic spectrograph, which then disperses a spectrum of a strip of the sky onto a charge-coupled device (CCD). A separate direct imaging system controls pointing and tracking, and both instruments share in tandem a computer-controlled mounting which permits automated data acquisition. The demonstrated optical performance is a 4 Åx11'' single-pixel resolution in a 4000 Åx3°.2 field. Absolute calibration on Vega gives a response at 6563 Å that is 7 times the CCD readout noise at an integrated exposure of 1 photon.cm^–2.Å^–1. Sample airglow, nebular, stellar, and cometary spectra illustrate the detection of extended emission features with fluxes from 5 to 2000 R. A measurement of zenith brightness for Na and Hg emission lines from urban artificial lighting is tabulated.