Initial Performance Tests of MASTA for Wide-Field Narrowband Imaging
Wide-field narrowband imaging provides an efficient approach for mapping low-surface-brightness line emission over large angular scales. We present initial performance tests of Multi-Application Survey Telescope Array (MASTA) for narrowband imaging. Using commissioning data obtained with the QHY461 and COSMOS-8K cameras, we characterize the basic reduction procedure, photometric calibration, image quality, and point-source detection limits. The measured surface-brightness and point-source detection limits become deeper with increasing exposure time, roughly following the expected background-limited scaling. Under the current observing and reduction conditions, the COSMOS-8K camera generally reaches deeper surface-brightness limits, particularly in the red filters, while QHY461 has smaller pixel size and provides better sampling of the telescope point spread function (PSF). As demonstrations, we perform continuum subtraction for the nearby galaxy M106 and the supernova remnant Cygnus Loop using adjacent narrowband filters and reveal the Hα and [O III] structures in M106 and filamentary structures in the Cygnus Loop. We further compare the MASTA surface brightness Hα map of M106 with an independent SITELLE measurement. After accounting for [N II] contamination and the wavelength-dependent response of the 6544 Å filter in the f /1.7 converging beam, the corrected median ratio is 0.973. These tests indicate that MASTA is a promising facility for wide-field narrowband imaging. Further improvements in calibration frames, including flux calibration, field-dependent bandpass characterization, and spatially varying PSF modeling and matching will be required for quantitative studies of diffuse ionized gas.