The University of Hawaii 2.2 Meter Fast Tip‐Tilt Secondary System

Jim, Kevin T. C.; Pickles, Andrew; Yamada, Haruka; Graves, J. E.; Stockton, Alan; Northcott, M. J.; Young, Tony T.; Cowie, L. L.; Thornton, Robert J.; Kupke, Renate; Sousa, E. Brook Chapman de; Cavedoni, Charles P.; Keller, Timothy; Nakamura, Wesley; Metzger, M.

doi:10.1086/316569

Cited by 9 publications

(3 citation statements)

References 26 publications

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“…Anecdotal evidence from other telescopes 9,10 suggests that the isokinetic angle for this type of correction is up to 3 arcmin. We will define three cases: (a) "pessimistic" with an isokinetic angle of 1 arcmin, (b) "neutral" with an angle of 2 arcmin, and (c) "optimistic" with an angle of 3 arcmin.…”

Section: Guide Star Availabilitymentioning

confidence: 98%

COATLI: an all-sky robotic optical imager with 0.3 arcsec image quality

et al. 2016

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COATLI will provide 0.3 arcsec FWHM images from 550 to 900 nm over a large fraction of the sky. It consists of a robotic 50-cm telescope with a diffraction-limited fast-guiding imager. Since the telescope is small, fast guiding will provide diffraction-limited image quality over a field of at least 1 arcmin and with coverage of a large fraction of the sky, even in relatively poor seeing. The COATLI telescope will be installed at the at the Observatorio Astronómico Nacional in Sierra San Pedro Mártir, México, during 2016 and the diffraction-limited imager will follow in 2017.

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Section: Guide Star Availabilitymentioning

confidence: 98%

COATLI: an all-sky robotic optical imager with 0.3 arcsec image quality

et al. 2016

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“…Tip-tilt secondary systems have been developed for telescopes to improve the image quality by correcting windinduced disturbances and by stabilizing telescope structural vibrations. In the University of Hawaii 2.2-m telescope, fast steering platform steers the f/31 convex secondary mirror of 214 mm in diameter and 25 mm in thickness (Cavedoni et al 1992;Jim et al 2000). Moerschell & Onillon (2001) presented a design of a tilt-chopping mechanism for the secondary mirror of the Stratospheric Observatory for Infrared Astronomy telescope.…”

Section: Introductionmentioning

confidence: 99%

“…To keep the operating momentum not to exceed the required limits, momentum compensated mass systems or velocity control systems have been used specially for small telescopes operated at high frequencies (Close & McCarthy 1994;Jim et al 2000;Stein & Neufeld 2004).…”

Section: Introductionmentioning

confidence: 99%

Random Vibration Analysis of the Tip-tilt System in the GMT Fast Steering Secondary Mirror

Lee¹,

Kim

Kim³

et al. 2017

PASP

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A random vibration analysis was accomplished on the tip-tilt system of the fast steering secondary mirror (FSM) for the Giant Magellan Telescope (GMT). As the FSM was to be mounted on the top end of the secondary truss and disturbed by the winds, dynamic effects of the FSM disturbances on the tip-tilt correction performance was studied. The coupled dynamic responses of the FSM segments were evaluated with a suggested tip-tilt correction modeling. Dynamic equations for the tip-tilt system were derived from the force and moment equilibrium on the segment mirror and the geometric compatibility conditions with four design parameters. Statically stationary responses for the tip-tilt actuations to correct the wind-induced disturbances were studied with two design parameters based on the spectral density function of the star image errors in the frequency domain. Frequency response functions and root mean square values of the dynamic responses and the residual star image errors were numerically calculated for the off-axis and on-axis segments of the FSM. A prototype of on-axis segment of the FSM was developed for tip-tilt actuation tests to confirm the ratio of tip-tilt force to tip-tilt angle calculated from the suggested dynamic equations of the tip-tilt system. Tip-tilt actuation tests were executed at 4, 8 and 12 Hz by measuring displacements of piezoelectric actuators and reaction forces acting on the axial supports. The derived ratios of rms tip-tilt force to rms tip-tilt angle from tests showed a good correlation with the numerical results. The suggested process of random vibration analysis on the tip-tilt system to correct the wind-induced disturbances of the FSM segments would be useful to advance the FSM design and upgrade the capability to achieve the least residual star image errors by understanding the details of dynamics.

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