Solc birefringent filter for several interesting spectral lines

Observing the Sun with birefringent filters is mainly done with filters tuned constantly on some 'interesting' spectral wavelength (H_alpha, KII). Technically, it is possible to design such a filter that transmits more than one interesting lines. It is described in this paper a Solc birefringent chain narrow-bandpass filter that allows observation on more than 30 interesting spectral lines (Hα , KII, Hγ, BaII, Hβ, D1, D3, etc.) and a solar spectrographic telescope that is able to meet demands for constant solar image scale in wavelength from 380 nm to 760 nm. The whole filter consists of three parts. Main part, consisted of 26 crystal quartz elements, provides transmittance of wanted lines. Frontal part consists of 12 oblique cut crystal quarts elements and provides cut off of neighbor maxima. Oblique cuts afford linear tuning by inclination of the part. The last part is narrow down Lyot element that provides a full width at half maximum of 0.05 nm and affords scan in ± 0.05 nm area (measurement of radial velocities). Tuning of the filter is solved by changing of its temperature at 10°C-60°C region and is provided by Peltier elements (cooling) and resistance heating. The telescope including the filter parts is designed as a unit providing a top quality imaging.