Speckle interferometry of visual binary stars in Merate (Italy)
The speckle interferometry of visual binary stars began in Merate
(Osservatorio Astronomico di
Brera, Italy) at
the end of the year 2003 with the installation at the Cassegrain focus
of the 1-meter Zeiss telescope of the speckle camera PISCO (acronym for
"Pupil Interferometry Speckle Camera and COronograph), from
Midi-Pyrénées Observatory, with the Intensified CCD
detector of Nice University. Since then, systematic observations
of
close visual
binary stars with such a device, in the context of an extensive
European collaboration including astronomers from Belgium, Bulgaria,
England, France, Italy and Poland were performed. In the year 2004, in
spite of some weeks lost because of technical problems and for painting
the
external side of the dome, 304 binary stars were observed, with a total
of 346 observations, mainly by Marco Scardia. Among those, 325
measurements led to the determination of the angular separation of the
components and the position
angle in the sky of the secondary star.
This first year of exploitation confirmed that the unit
1-meter Zeiss reflector + PISCO allows to observe close binaries down
to a minimum separation of 0"14,
with a magnitude difference
between
the components up to 4, and a limiting V magnitude of 9.5. The
accuracy is about 0"01 in
angular separation and 0.5° in position
angle. The data collected allowed the revision of some orbits.
As an
example, the graph of the apparent orbit of the double star BU 1077 --
ADS 8035 is reported in Fig. 1. Such orbit is
mainly based on
the observations made with PISCO at Pic du Midi and Merate. The
histogram in Fig. 2 shows the distribution
versus the class of angular
separation of 325 mesurements made in 2004. For the
remaining 21 observations it was not possible to obtain reliable
measures because of the extreme closeness of the components, below the
diffraction limit of the telescope, or the bad quality of the images.
On November 2004, during a stay in Merate, Jean-Louis Prieur
(Midi-Pyrénées Observatory) revised and
implemented the image acquisition and reduction software. The
observations collected in the first half of 2004 have been already
published, whereas a second publication with the ones of the second
half-year is in press (see list of publications).
Fig. 1: Apparent orbit of the double star BU 1077 -- ADS 8035.
Fig. 2. Statistics of the 325 double star
observations made in Merate
in 2004 with PISCO at the 1 meter Zeiss telescope.
Fig. 3. A grating was placed on the top of the
Zeiss Telescope in November 2005, to calibrate the PISCO scale.
This
text was largely inspired from the Merate Annual report of 2004
(Annuario 2004)
