You are an expert at summarizing long articles. Proceed to summarize the following text: 
we report on the development of the medium resolution spectrophotometer to accompany ( in real time ) spectral observations performed with the high resolution spectrographs  @xcite on the 6meter telescope bta of the special astrophysical observatory . the spectrophotometer uses a 0.7meter optics of the bta guide telescope and have a separate system for object positioning . the spectrophotometer is managed via the internet .    in high resolution ( r ) spectral observations on the bta the size of the spectral region simultaneously recorded depends mainly on the format of ccd used . for example , the spectral region simultaneously recorded with the nasmyth echelle spectrograph ( nes ) is equal approximately to 1000 , 1500 , 3000 at the ccd format 1k@xmath01k , 2k@xmath02k , 2k@xmath04k . spectral lines measured in these regions are used for modeling of stellar atmospheres by comparing of theoretical and observational parameters of lines . adequacy of the model could be checked through comparison both theoretical and observational spectral energy distribution . but for such a procedure a photospheric continuum must be registered in broader spectral region , i.e. we need low resolution spectrophotometric observations . for example , spectrophotometric data for stars in pleiades were obtained within 3200@xmath17900 region with r=130  @xcite . auxilliary spectrophotometric observations of nonstationary stars must be performed in the equal time with the high and low resolution spectroscopy . howerever such a regime it is difficult to organize in practice . bta was equipped with the auxilliary reflector having focus 12 m and diameter of the mirror 0.7 m ( fig.[fig1 ] ) , which has worked before middle 80th as a guide system  @xcite . we analysed the suitability of this reflector for spectrophotometric observations making simultaneous with high resolution spectroscopy with a main mirror of the bta . the spectrophotometer has to provide the following properties . first , registration time at the 0.7m telescope can not exceed time registration of high resolution spectrum at the bta . this condition limits a value of spectral resolution of the spectrophotometer . second , the optics of the 0.7m telescope has to be achromatic . therefore we removed th two - lenses corrector , after that the effective focal distance of the new layout is equal to 7.8 m . third , the spectrophotometer has to have an autonomous system to positioning of the star at the input , which has to being independent of the actions of the observer at the bta . the layout developed is shown in fig.[fig2 ] . the dekker s size was selected aiming to catch a star image distorted by atmospheric dispersion . the diameter of the collimated beam is equal to 32 mm . as a cross disperser the abbe prism is used which allows to place main elements of the spectrophotometer in the plane parallel to back plane of reflector mirror . we used the echelle grating r2 with grooves density 75gr / mm and the objective f=120 mm . as a local corrector a planeparallel detail ruled by bending in two perpendicular axes is used  @xcite . when a star image wholly get into the dekker , the spectrophotometer works as slitless and spectral resolution is determined mainly by accuracy of the star retention on the dekker . therefore we use a second layout of guiding  inside the spectrophotometer  @xcite . optical elements of this second layout of guiding are not shown in fig.[fig2 ] .
we report on the development of the medium 
 resolution spectrophotometer to accompany ( in real time ) spectral observations performed with the high resolution spectrographs on the 6-m telescope bta .