Stereoscopic Spectroscopy for Efficient Spectral Imaging and Magnetography

Abstract

Stereoscopic imaging spectroscopy is a novel technique that uses multiple spectral orders and stereoscopic reconstruction to eliminate the need for a slit in a dispersive spectrograph, potentially increasing photon efficiency by 1-2 orders of magnitude compared with conventional spectral imaging. We present advances in stereoscopic reconstruction, allowing detection of the first moments of a spectral line simultaneously over a complete two-dimensional image plane. Using the Advanced Stokes Polarimeter on the Dunn Solar Telescope at the National Solar Observatory, we have created the first solar magnetograms made with this technique. With a simple prototype optical layout, we were able to generate Stokes V magnetograms using the Fe I photospheric absorption line at 617.34 nm (6173.4 A). We calculate that an optimized instrument using this technique could acquire solar magnetograms with ~10 G rms shot noise in 150 ms using this spectral line at the host telescope's diffraction limit. Stereoscopic techniques are useful not only for the solar photosphere but also for photon-starved imaging spectroscopy in general.