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 ζ Orionis A, obtaining a flux ratio of 2.18 ± 0.13 with a position angle of 223.9 ± 1.0 • and separation 40.6 ± 1.8 mas over 570-750 nm, in good agreement with expectations from the previously published orbit.2. Mount the 70 /20 beam splitters and accompanying beam-shear compensating windows. The beam splitters route light from the feed system to the VISION optical bench.

The Navy Precision Optical Interferometer (NPOI) has two purposes: wide angle precise astrometry and high-resolution imaging, both at visible wavelengths. It operates with up to six 12-cm diameter apertures simultaneously, with baseline lengths (distances between array elements) from 16 m to 79 m, and disperses the combined light into 16 spectral channels. It has been operational since first fringes were found in 1994; six-beam operations began in 2001. The NPOI is undergoing upgrades in numerous areas: control system and data acquisition improvements, a second beam combiner, additional array stations for both longer and shorter baselines, and supplemental delay lines to improve sky coverage for the longer baselines. Future possibilities include the installation of four fixed 1.8 m telescopes as well as up to six moveable lightweight 1.4 m telescopes. Observing programs, including programs led by outside investigators, cover a broad range of stellar astrophysics as well as observations of geostationary satellites.

An innovative compact-yet high resolution-cross-dispersed echelle spectrograph has been designed, built, and deployed at TSU's 2-meter robotic telescope for initial tests and commissioning. This design is based on a single mode fiber (SMF) and it eliminates mode noise in fiber-fed spectrographs which is important for m/s precision exoplanet Doppler searches. The use of SMFs removes modal variation, makes the design compact and the camera focus slow and stable at the price of lower throughput. This can be improved by using adaptive optics or by placing it in space; the compact design is well suited for such deployment.

We used the Palomar Testbed Interferometer (PTI) to resolve 2.2 µm emission from the classical nova V458 Vul 2007 over the course of several days following its discovery on 2007 August 8.54 UT. We also obtained K-band photometric data and spectra of the nova during the early days of the outburst. We also used photometric measurements from the AAVSO database. This is a unique data set offering a 3-technique approach: high-resolution imaging, spectroscopy and photometry. Our analysis shows that the nova ejecta can be modeled as an inclined disk at low inclination i.e. low ellipticity which is consistent with the nova being in the fireball phase at which the outflowing gas is optically thick, confirmed by the presence of strong P-Cygni Balmer lines in the spectra. The expansion velocity is ≈1700 km s −1 , derived from the Hα line. By combining the nova's angular expansion rate measured by PTI with the expansion rate measured from spectroscopy, the inferred distance to the nova is 9.9-11.4 kpc. We also used the K-band fluxes and the derived size of the emission to estimate the total mass ejected from the nova ≈ 4 × 10 −4 M ⊙ . The quick transition of the nova from Fe II to He/N class makes V458 Vul 2007 a hybrid nova.

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