In this work we decided to concentrate on the region 50–380 Å for which the grazing incidence grating spectrograph is the most suitable instrument. This portion of the spectrum contains many rather intense lines lying very close together which arise primarily from very highly ionized atoms in the solar corona. Wavelength measurements and identifications have been made for a portion of the lines, but for many of them, especially the weaker ones, the situation was not completely clear and many doubts existed. Therefore we decided to build a rocket spectrograph which would significantly improve the resolution and wavelength accuracy for lines in the solar spectrum. Thus, we attempted to achieve wavelength accuracy of 0.003 Å and to limit the instrumental broadening of the lines to 0.03 Å.