Diffraction-Limited Imaging II. Optical Aperture-Synthesis Imaging of Two Binary Stars
We have used the technique of nonredundant masking at the Hale 5 m telescope and radio VLBI imaging software are used to make optical aperture-synthesis maps of two binary stars, β Corona Borealis and σ Herculis. The dynamic range of the map of β CrB is about 50:1. For σ Her, we find a separation of 70 milliarcsec. These maps demonstrate the potential of the nonredundant masking technique for diffraction-limited imaging of astronomical objects with high dynamic range. We find that the optimal integration time for measuring the closure phase is found to be longer than that for measuring the fringe amplitude. There is not a close relationship between amplitude errors and phase errors, as is found in radio astronomy, and amplitude self-calibration is less effective at optical wavelengths than at radio wavelengths. The primary beam sensitivity correlation made in radio astronomy is not necessary in optical interferometry.
Additional InformationCopyright 1989 American Astronomical Society. Received 17 January 1989; revised 7 February 1989. We would like to thank E. Emery, F. Harris, and R. Nadler for the professional engineering of the observing and data acquisition systems. We thank A. Lee and G. Smith for excellent programming for the peripherals of the data-acquisition system. We also thank the mountain staff at the Palomar Observatory for assistance with the setup and observations. We would like to thank T. Pearson for assistance with the VLBI software. We thank the W. M. Keck Foundation for financial support. P. W. G. and T. A. P. acknowledge support from Department of Energy grant no. DE-FG-03-85ER25009 and National Science Foundation grant no. AST8351736. T. N. thanks the Schlumberger Fellowship.
Published - 1990-16.pdf