|  | 
				
					| High resolution spectrographs 
					 |  
					| High resolution spectroscopy offers great insight in the details of stellar 
						structure and stellar evolution. Compared to low and medium resolution work, 
						details in stellar spectra become accessible and the comparison between model 
						and observation can be revised at a unique level. The picture to the right 
						shows the solar hydrogen Balmer line “beta” at high and medium resolution. 
						Notably more details are observed in high resolution mode. |  |  
					| In order to obtain spectra of high resolution, reaching from resolving 
						powers R=40000 to R=100000 more and more telescopes are equipped with high 
						resolution spectrographs. |  
				
				   	|  | Changing from photographic plates to modern electronic CCD detectors, that 
						are usually produced in squared or rectangular geometry, a spectrograph 
						configuration, that does not produce one linearly extended long spectrum, 
						but a set of spectral “stripes” that lie beneath each other became extremely 
						important. This Échelle type spectrographs allow to use highly efficient 
						two dimensional and rectangular  detectors to register a large part of the 
						spectrum in one exposure. |  
					| As it becomes necessary to spread the spectrum twice in wavelength space, 
						first along the major dispersion direction by a grating and a second time 
						in order to separate the single spectral orders perpendicular to the major 
						dispersion axes two dispersing elements are needed in an  Échelle spectrograh. |  
				
					| The picture to the right shows the basic geometry of the two spectrographs 
						FOCES and LAMOST HiRes. The first has been built in our group and is 
						currently successfully installed at the 2.2m 
						Calar Alto telescope. 
						The latter spectrograph is under design in a Sino-German project and is 
						planned to see its first light at the 
						 LAMOST telescope in 
						Xinglong station China end of 2008. |  |  |  |