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		| Paper: | 
		Kees Zwaan, open principle, future of high-resolution solar telescopes | 
	 
	
		| Volume: | 
		470, 370 Years of Astronomy in Utrecht | 
	 
	
		| Page: | 
		381 | 
	 
	
		| Authors: | 
		Hammerschlag, R. H.; Bettonvil, F. C. M. | 
	 
	
	
		| Abstract: | 
		It was around the 1970s that during site-test campaigns masts were erected up till 30 m height with sensors at several heights for the measurement of temperature fluctuations. Kees Zwaan discovered that the fluctuations decrease drastically at heights from about 15 m and upward when there is some wind. The conclusion from this experience was the open telescope principle: a telescope completely free in the air 15 m or more above the ground. The Dutch Open Telescope (DOT) was the pioneering demonstrator of the open-telescope technology. Now that larger high-resolution telescopes come in view, it is time to analyze again the principle: the essentials for proper working of the open principle and the design consequences for the new generation of high-resolution solar telescopes. | 
	 
	
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