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		| Paper: | 
		From Hubble's Next Generation Spectral Library (NGSL)   to Absolute Fluxes | 
	 
	
		| Volume: | 
		503, Calibrating Large Surveys and Future Facilities | 
	 
	
		| Page: | 
		211 | 
	 
	
		| Authors: | 
		Heap, S. R.; Lindler, D. | 
	 
	
	
		| Abstract: | 
		Hubble's Next Generation Spectral Library (NGSL) consists of R∼1000 spectra of 374 stars of assorted temperature, gravity, and metallicity.  Each spectrum covers the wavelength range, 0.18–1.03  μ. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsl/. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We have therefore developed an observing procedure, data-reduction procedure, and correction algorithms that should yield fluxes with uncertainties less than 1%. | 
	 
	
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