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		| Paper: | 
		Open Cluster Distances from Hipparcos parallaxes | 
	 
	
		| Volume: | 
		167, Harmonizing Cosmic Distance Scales in a Post-Hipparcos Era | 
	 
	
		| Page: | 
		52 | 
	 
	
		| Authors: | 
		van Leeuwen, Floor | 
	 
	
	
		| Abstract: | 
		An overview is presented of Hipparcos parallax determinations for open clusters. The reliability of these determinations is considered in a discussion about the size and scale of local systematic correlations in the Hipparcos parallax errors. Localized correlations between Hipparcos parallax errors are found to be at a level of at most 0.1~mas, disappearing beyond separations of 1.2deg. There is no sign of significant large scale distortions. Formal errors as found for the cluster parallaxes are therefore a realistic reflection of their true accuracy. A composite HR diagram for the 10 nearest open clusters confirms this, by showing systematic behaviour as a function of cluster age similar to, but much more pronounced than, what can be observed from theoretical isochrones. | 
	 
	
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