First sky fringes (21 March 2004)
21 March 2004, by
During the night of the South Hemisphere Autumn, AMBER has displayed the first fringes obtained on a star. The observed star was Theta Cen with a K=-0.2 magnitude. AMBER was located at the focus of the VLTI and operated with 2 siderostats placed at the D0 and H0 location (64 m almost E-W baseline). The visibility value of Theta Cen was around 60%.
The fringes were obtained after checking on Sirius the co-alignement between AMBER and the VLTI. Unfortunately Sirius was setting around midnight, and another bright star had to be selected. The seeing was of the order of 1 arcsec. We had no indications of the value of the zero optical path difference. We had to move the delay line at 8.2mm from its initial position to see the fringes in the AMBER low spectral resolution mode. Unfortunately we had not been able to record data but 8 persons were present to validate the presence of the fringes. We selected the medium spectral resolution mode in order to record data, but the light level seemed to be too low. Subsequent data reduction will tell us if the fringes were indeed present. This first successful run, allowed to pinpoint several improvements to be made in the observing software. We are therefore confident to get nice fringe data during the coming week.
Sunday 21 March has been dedicated to the check of the Atmospheric Dispersion Module (ADC) and no sky tests have been planned. Sky observations should continue on Monday.
Of course, the first fringes have been celebrated with champagne... We thank all the AMBER team for this first result (see R. Petrov letter).
More pictures are available at Andrea Richichi’s site http://www.eso.org/~arichich/downlo...