The NAOS visible wave front sensor
This paper describes the Visible Wave Front Sensor (visible WFS) for the VLT Nasmith Adaptive Optics system (NAOS). This Shack-Hartman-based wave front sensor instrument includes within a continuous flow liquid nitrogen cryostat: - a low noise fast readout CCD camera controlled by the ESO new generation CCD controller FIERA. The readout noise of this system is 3 e- at 50 kilopixel/sec/port, and is only limited by the CCD intrinsic noise. FIERA proposes remotely controlled readout modes with optional binning, windowing and flexible integration time. - two remotely exchangeable micro-lens arrays focusing the analyzed wave front directly on the CCD sensitive surface. The wave front sensor includes also its own atmospheric dispersion compensator. Due to the continuous rotation of the NAOS adapter, the mechanical stiffness of the visible wave front sensor must be very high not to disturb the loop operation (no more than 0.1 μm of lenslet array displacement compared to the CCD location over a 30° rotation angle of the instrument). The following simulations and tests are described: - simulation results providing an estimation of the NAOS maximum operating magnitude - camera optimization - mechanical stiffness measurements.
Status of the VLT Nasmyth adaptive optics system (NAOS)
NAOS is the adaptive optics system to be installed at one of the Nasmyth focus of the VLT. It was designed and manufactured by a French Consortium to provide compensated images to the high angular resolution IR spectro-imaging camera (CONICA) in the 1 to 5 micrometer spectral range. For bright sources, NAOS will achieve a Strehl ratio of 70% under average seeing conditions. It is equipped with a 185 actuator deformable mirror, a tip/tilt mirror and two wavefront sensors, one in the visible and one in the near IR. All the components of NAOS have been delivered and the integration phase is in progress since the beginning of 2000. After extensive tests and performance verifications in France, the system will be shipped to Chile by the end of 2000. The first light at the VLT is foreseen in the beginning of 2001.
Looking for regional words in late seventeenth-century England: Bishop White Kennett and his glossary to Parochial Antiquities (1695) 1
The analysis of regional dialects in the Early Modern period has commonly been disregarded in favour of an ample scholarly interest in the ‘authorised’ version of English which came to be eventually established as a standard. The history of regional ‘Englishes’ at this time still remains to a very great extent in oblivion, owing mainly to an apparent dearth of direct textual evidence which might provide trustworthy data. Research in this field has been for the most part focused on phonological, orthographical and morphological traits by virtue of the rather more abundant information that dialect testimonies yield about them. Regional lexical diversity has, on the contrary, deserved no special attention as uncertainty arises with regard to what was provincially restricted and what was not. This paper endeavours to offer additional data to the gloomy lexical setting of Early Modern regional English. It is our aim to give a descriptive account of the dialect words collated by Bishop White Kennett’s glossary to Parochial Antiquities (1695). This underutilised specimen does actually widen the information furnished by other well known canonical word-lists and provides concrete geographical data that might contribute to bridging the gaps still existing in the history of lexical provincialisms at the time.