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Direct measurements of wind disturbances forces on the CTIO Blanco 4m telescope mount and its effect in tracking jitter
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Paper Abstract

Since the CTIO 4m Blanco Telescope was successfully upgraded, commissioned, and integrated with the DECam Instrument in Sept 2012, the performance of the telescope mount tracking has been excellent, with a median tracking jitter of 0.025”, and 0.06”rms, for the declination, and right ascension axes respectively. Any occasional increase in mount tracking jitter, has been associated with wind induced torque disturbances, affecting both axes simultaneously, especially during high speed wind conditions, combined with dome, and wind direction alignment.

In order to investigate the response to the telescope mount servo control, to wind induced disturbances, we have instrumented the 4m Blanco Telescope mount, upper secondary ring, with a novel 2-axis direct wind force sensor, sampled at 200 Hz, using inexpensive pocket digital scale type load cells, this combined with a small surface area of 0.00375 m2, we have obtained wind pressure noise values of 0.4 Pa-rms.

Our investigation will compare the Power Spectral Density (PSD) of the wind disturbance forces, with the expected Kolgomorov model, and explore the correlation between wind disturbance forces, and mount tracking jitter.

Also we will establish under what dome, wind direction, and wind speed conditions the increased mount tracking jitter, could affect science image results, and cause an increase in image ellipticity, and FWHM. This information should help observers, in taking appropriate measures, to minimize the wind induced image degradation in the future.

Paper Details

Date Published: 6 July 2018
PDF: 11 pages
Proc. SPIE 10700, Ground-based and Airborne Telescopes VII, 107000J (6 July 2018); doi: 10.1117/12.2311479
Show Author Affiliations
Michael Warner, Cerro Tololo Inter-American Observatory (Chile)
Norman Diaz, Cerro Tololo Inter-American Observatory (Chile)

Published in SPIE Proceedings Vol. 10700:
Ground-based and Airborne Telescopes VII
Heather K. Marshall; Jason Spyromilio; Roberto Gilmozzi, Editor(s)

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