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16 June 2000 Pointing and tracking software for the TNG telescope
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The Telescope Nazionale Galileo (TNG) telescope is now operational. One of its main goals is to provide high quality images, in a wide range of operating conditions and for several observing modes. Telescope pointing and tracking performances can heavily affect achievement of this requirement, and particular care must be taken in order to reach the highest possible accuracy. Control of the three axes is implemented in one VME controller (minimizing data exchange through the TNG LAN), and telescope mount positions are computed from object coordinates taking into account physical and environmental aspects which alter the object apparent position. Improvement of telescope pointing and tracking performances is obtained by two means. Systematic errors are mostly corrected using a model compensation, that can be introduced in the coordinates transformation flow. The telescope model is derived by off-line analysis of the pointing errors on a specific set of data. In this way we could improve the pointing and tracking performances up to now by a factor of about 30. Tracking drift given by non- systematic and residuals of systematic errors is corrected using a guide camera, which mounts a 800 X 576 CCD (0.35 arcsec/pixel scale). Guide stars are selected from an on- line available star catalogue. Light from the selected star is focused on the guide camera by moving a probe housed in the rotator-adapter module. Tracking drift computation is performed on a two-axes scheme (Right Ascension and Declination), with sub-pixel accuracy. Here the first results of the telescope pointing and tracing accuracy are presented.
© (2000) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Daniele Gardiol, Carlotta Bonoli, Leonardo Corcione, Enrico Giro, and Andrea Zacchei "Pointing and tracking software for the TNG telescope", Proc. SPIE 4009, Advanced Telescope and Instrumentation Control Software, (16 June 2000);


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