1 June 1994 Control of image position errors with the VLT
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An important contributory factor to the overall quality of the images obtained with the VLT are random tilt errors caused by wind buffeting and the atmosphere. The techniques and strategy adopted to overcome these errors are described. Image position errors caused by wind buffeting are minimized, as far as possible, by optimizing the configuration of the telescope enclosure for the prevailing wind and observing conditions. Residual tilt errors are reduced to acceptable limits by the use of a secondary mirror tilt-tip mechanism in conjunction with the telescope axis control system. In situations where the ratio of D/r0 is small, atmospheric tilt can contribute the dominant source of tilt error. In these cases the same correction procedure using the secondary mirror can even improve the image quality beyond the long integration atmospheric limit. Possible control schemes and results of simulations are presented to demonstrate the effectiveness of these solutions. The limitations of the techniques are discussed as well as their value compared to a full wavefront correction of the VLT adaptive optics system.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Martin J. Cullum, Daniel Enard, Martin Ravensbergen, "Control of image position errors with the VLT", Proc. SPIE 2199, Advanced Technology Optical Telescopes V, (1 June 1994); doi: 10.1117/12.176270; https://doi.org/10.1117/12.176270

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