Speckle observations with PISCO in Merate (Italy) - VII. Astrometric measurements of visual binaries in 2007
Résumé
We present relative astrometric measurements of visual binaries made during the first semester of 2007, with the speckle camera PISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. We obtained 226 new measurements
of 214 objects, with angular separations in the range 0 ′′ .15 — 4 ′′ .5, and an average accuracy of 0 ′′ .013. The mean error on the position angles is 0 ◦ .7. Most of the position angles could be determined without the usual 180 ◦ ambiguity with the application of triple-correlation techniques and/or by inspection of the long integration files.
We also present the new orbits we have computed for ADS 7871, 7982 and 8128, for which our measurements lead to large residuals and/or for which the revision is justified by the significant number of observations made since computation of the last orbit.
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