This applet will provide students with a database of real stellar and galaxy spectra and a tool from which the equivalent width of a spectral feature can be measured. The tool allows the wavelength range of the spectral feature to be marked and a reference continuum point can be chosen. From this, the integrated spectral flux of the feature is converted into its equivalent width and reported. This applet can be used for instance to show how the strength of hydrogen lines changes as a function of temperature of a stellar atmosphere, or how the strengths of some metal lines (Calcium) depend on this, or how the shape of the continuum changes with temperature.