R. Ragazzoni, A. Baruffolo, J. Farinato, A. Ghedina, E. Marchetti,
S. Esposito, L. Fini, P. Ranfagni, F. Bortoletto, M. D'Alessandro,
M. Ghigo, G. Crimi
The final commissioning phase of the AdOpt@TNG module.
Abstract
The AdOpt@TNG module is an adaptive optics facility permanently mounted at
the Nasmyth focus of the 4m-class Telescopio Nazionale Galileo (TNG). Its
integration on the telescope started in late November 1998 and first-light
of the speckle and tip-tilt modes took place shortly after. Both modes
have been offered to the astronomical community and turned out to provide
performances close to the expectations. Double stars with separation
below 0.1arcsec have been resolved by the speckle facility. Improvement
of the Strehl ratio of a factor two and enhancement in the FWHM from
0.65arcsec to 0.35arcsec have been obtained on relatively faint reference
stars. The high-speed low noise CCD, namely an 80x80 pixel read from
the four corners, has been mounted and aligned with the Shack-Hartmann
wavefront sensor. A Xinetics mirror with 96 actuators has been calibrated
against the wavefront sensor with on-board alignment fibers. This has been
done using a modal approach and using Singular Value Decomposition in
order to get a reliable interaction matrix. Filtering can be modal too,
using a default integrative filter coupled with a limited FIR-fashioned
technique. Open loop measurements on the sky provide data to establish
open loop transfer functions and realistic estimates of limiting
magnitude. High-order wavefront correction loop has been succesfully
tested on the sky. In this paper we give a description of the overall
functionality of the module and of the procedure required to acquire
targets to be used as reference in the correction. A brief overview of
the very first astronomical results obtained so far on angular size and
shape measurements of a few asteroids and sub-acrsec imaging of Planetary
Nebulae and Herbig Haro objects is also given.