EDP Sciences
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Volume 378, Number 3, November II 2001
Page(s) 1100 - 1106
Section Instruments, observational techniques and data processing
DOI http://dx.doi.org/10.1051/0004-6361:20011239

A&A 378, 1100-1106 (2001)
DOI: 10.1051/0004-6361:20011239

CCD drift-scan imaging lunar occultations: A feasible approach for sub-meter class telescopes

O. Fors1, 2, J. Núñez1, 2 and A. Richichi3

1  Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain
2  Observatori Fabra, Camí de l'Observatori s/n, 08035 Barcelona, Spain
3  European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany

(Received 15 May 2001 / Accepted 16 August 2001)

A CCD drift-scanning technique for lunar occultation (LO) observations is presented. While this approach has been addressed before by Sturmann ([CITE]) for the case of large telescopes, the technical validity has never been discussed for sub-meter class telescopes. In contrast to Sturmann's scheme, the proposed technique places the CCD in the image plane of the telescope. This does not represent a problem in the case of small telescopes, where the practical angular resolution attainable by LO is not limited by aperture smoothing. Photon-generated charge is read out at millisecond rates on a column by column basis, as the diffraction pattern of the occulted star is being tracked. Two LO events ( SAO 79031 and SAO 77911 ) were observed to demonstrate the feasibility of the method. Data analysis was carried out, yielding unresolved angular diameters for both objects. We show, however, that the technique could be useful for close binary detections with small telescopes. A discussion of the limiting resolution and magnitude imposed by our instrumentation is carried out, showing that the drift-scanning technique could be extended to 1-2 m telescopes for stellar diameter determination purposes. Finally, we point out that the technical demands required by this technique can be easily met by most small professional observatories and advanced amateurs.

Key words: instrumentation: detectors -- techniques: high angular resolution -- occultations -- stars: fundamental parameters -- stars: binaries: general

Offprint request: O. Fors, ofors@am.ub.es

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