Visible-light long baseline interferometry holds the promise of advancing a number of important applications in fundamental astronomy , including the direct measurement of the angular diameters and oblateness of stars , and the direct measurement of the orbits of binary and multiple star systems .
To advance , the field of visible-light interferometry requires development of instruments capable of combining light from 15 baselines ( 6 telescopes ) simultaneously .
The Visible Imaging System for Interferometric Observations at NPOI ( VISION ) is a new visible light beam combiner for the Navy Precision Optical Interferometer ( NPOI ) that uses single-mode fibers to coherently combine light from up to six telescopes simultaneously with an image-plane combination scheme .
It features a photometric camera for calibrations and spatial filtering from single-mode fibers with two Andor Ixon electron multiplying CCDs .
This paper presents the VISION system , results of laboratory tests , and results of commissioning on-sky observations .
A new set of corrections have been determined for the power spectrum and bispectrum by taking into account non-Gaussian statistics and read noise present in electron-multipying CCDs to enable measurement of visibilities and closure phases in the VISION post-processing pipeline .
The post-processing pipeline has been verified via new on-sky observations of the O-type supergiant binary \zeta Orionis A , obtaining a flux ratio of 2.18 \pm 0.13 with a position angle of 223.9 \pm 1.0 ^ { \circ } and separation 40.6 \pm 1.8 mas over 570-750 nm , in good agreement with expectations from the previously published orbit .