Characterization of the commercial spectrograph system for astronomical observations: PIXIS 1300BX Camera and IsoPlane 320A Spectrograph

Abstract

We present the result from a comprehensive laboratory and on-sky characterization of the commercial spectrograph system consisting of a PIXIS 1300BX charge-coupled device (CCD) camera and an IsoPlane 320A spectrograph as part of the preparation of the forthcoming all-sky spectroscopic survey of nearby galaxies (A-SPEC). In the laboratory, we have quantified readout noise, dark current, gain, and full-well capacity via bias, dark, and photon transfer curve analysis at all acquisition modes. To do that, we have developed a gradient correction technique to address row-dependent signal gradients in the image, which are caused by the shutter-less condition of our CCD camera test setup. The technique successfully reproduces the values in the manufacturer specifications. We also have measured quantum efficiency exceeding 80% from 400--800 nm and $\gtrsim$ 90% between 450--750 nm, with sub-second persistence decay, making it ideal for rapid, multi-object spectroscopy. Using a set of diffraction gratings (150, 300, and 600 gr mm$^{-1}$), we have evaluated the spatial separability of multiple spectra and spectral resolution. We have conducted a test observation with this spectrograph system at the Seoul National University Astronomical Observatory (SAO) 1 m telescope and successfully demonstrated its capability of multi-object spectroscopy with moderate resolution of $R \approx 600 - 2600$. We release all Python codes for the test and recipes to facilitate further instrument evaluations.