Abstract
The unusual ultraviolet excesses of HD 25329 and HD 122563 are explained by their nitrogen abundances (absorption by the 3360A (0-0) and 3370A (1-1) bands of NH) and by Rayleigh scattering. For 45-63 + 1.0 eight-color photometry can be used to identify (metal poor) dwarf stars with nitrogen overabundances. The difference curve of the extremely metal-poor giant HD 122563 shows very distinctly the increased importance of Rayleigh scattering with respect to the H - processes as a source of continuum opacity. .
