STIS Instrument Handbook for Cycle 24 . ... Should I Use COS or STIS? ... In this wavelength range, the throughput of the COS FUV channel exceeds that of the STIS FUV -MAMA by factors of 10 to 30, and the combination of the spectroscopic resolving power (~ 20,000) and wavelength coverage (300 to 370 е per setting) of the medium- resolution COS FUV modes results in a discovery space (throughput times wavelength coverage) for observations of faint FUV point ...