Data were recorded during two observing runs in September 1994 and December 1995 at the 2 m TBL. A total of 20 double stars and a triple star (2Cam) were observed during five nights. Details are given in Table 1 (click here). One star (SAO 12917) was discovered as double during the 1995 run. As its measurement has been already published in a research note (Carbillet et al. 1996a) this star will no more appear in the present paper.
| ADS | Star | Reference | Epoch |  |  | Sampling | Notes |
| number | name | star | (nm) | (ms) | (mas/pixel) | ||
| 434 |  Cas |  Cas | 1995.951 | 528/69 | 16 | 30.8 | |
| 1615 |  Psc |  Cet | 1995.951 | 528/69 | 16 | 30.8 | 1 |
| 1860 |  Cas | SAO 12031 | 1995.951 | 528/69 | 16 | 30.8 | 1, 3 |
| 2616 | 7 Tau | SAO 75912 | 1995.951 | 684/69 | 16 | 30.8 | 1, 3 |
| 2755AB | ADS 2755C | 1995.951 | 684/69 | 16 | 30.8 | 1, 3 | |
| 3358 | 2 Cam | SAO 24531 | 1995.940 | 684/69 | 11 | 30.8 | |
| 3711 | 14 Ori | SAO 112556 | 1995.951 | 684/69 | 5 | 30.8 | 2, 3 |
| 3728 | SAO 112308 | 1995.951 | 684/69 | 5 | 30.8 | 3 | |
| 4115 | 32 Ori |  Ori | 1995.930 | 684/69 | 16 | 11.9 | 1, 3 |
| 5447 | SAO 95996 | 1995.951 | 684/69 | 5 | 30.8 | 3 | |
| 5925 | SAO 152663 | 1995.951 | 684/69 | 16 | 30.8 | 3 | |
| 7307 | SAO 42876 | 1995.930 | 684/69 | 16 | 11.9 | 3 | |
| 8035 | Uma |  Uma | 1995.940 | 684/69 | 0.4 | 30.8 | |
| 10360 | c Her | 59 Her | 1994.696 | 658/42.5 | 16 | 11.9 | |
| 12973 |  Sge | HR 7536 | 1994.696 | 658/42.5 | 16 | 11.9 | |
| 14073 | Del | 
Del | 1994.693 | 658/42.5 | 16 | 11.9 | |
| 14773 | Equ |  Aql | 1994.693 | 658/42.5 | 16 | 11.9 | 3 |
| 14787 | Cyg | - | 1994.693 | 658/42.5 | 13 | 11.9 | |
| 15281 |  Peg | - | 1994.696 | 658/42.5 | 16 | 11.9 | |
| 16057 | SAO 10131 | 1995.940 | 684/69 | 16 | 30.8 |
The speckle camera was developed by the Aperture Synthesis group of
Observatoire Midi-Pyrénées
(André et al. 1994; Prieur et
al. 1994). It allows different magnifications of the focal
image, has a filter wheel equipped with B, V, R interferential filters
and compensates the atmospheric refraction by means of Risley prisms. The
speckle camera was put at the f/25 Cassegrain focus of the TBL. The
angular field of view was 
for the observations of
1995, 
for the observations of 1994.
The detector is an intensified video CCD (Philips IP800T). The images are
sampled by a 290
774 pixels CCD matrix. The effective pixel size at
the front of the intensifier is 17.7 
m 32.9 m. Exposure
time ranges from 64 s to 16 ms. Video signal is transferred to the
observation room by fiber optics. Images are recorded on S-VHS tape using a
Panasonic AG-7355. Local processing is made by a NeXT Cube computer with a
NeXT Dimension video digitizer. This local processing is far from real-time
since the transfer rate is of the order of 2 images per second for a
256256 sub-image. Post-processing is made with the same computer
driving the video recorder via a RS-232C line and reading the tape frame by
frame.
Each binary star and its reference star were observed about 20 minutes. The
reference stars have been chosen of similar magnitude and spectral type as
the double stars, to reproduce the same observing conditions for the
detector. The limiting magnitude of the experiment is about V=10 for
medium seeing conditions (
).
Calibration for the spatial sampling was made by putting a grid into the focal plane. The angular calibration was made by trailing a star across the field in right ascension and declination. The images taken in 1994 were oversampled with 119 mas per pixel, whereas the speckle size was 61 mas at 490 nm (the shortest wavelength available). In 1995 we used a lower magnification and the pixel size was just half of the speckle size at 490 nm (Nyquist criterion).
the bandwidth.