Simonetti, John H.Dennison, B.Topasna, G. A.2014-03-102014-03-101996-02John H. Simonetti et al. 1996 ApJ 458 L1 doi:10.1086/3099150004-637Xhttp://hdl.handle.net/10919/25859We made a sensitive, wide-field Ha image of the north celestial polar region. Using this image, we constrain the contribution of irregularities in interstellar free-free emission to the degree-scale anisotropies in the cosmic microwave background detected in recent observations at Saskatoon by the Princeton group. The analysis of the Her image mimics the Saskatoon data analysis: the resulting signal is the strength of irregularities sampled with the Saskatoon beam (i.e., degree-scale) along the 85 degrees declination circle. We found no such irregularities that could be attributed to Her emission. The implied upper bound on the rms variation in free-free brightness temperature is less than 4.6 mu K at 27.5 GHz. The observed cosmic microwave background anisotropies are much larger. Therefore, the contribution of irregularities in interstellar free-free emission to the observed anisotropies is negligible.en-USIn Copyrightcosmic microwave backgroundinstrumentation, miscellaneousism,generalradiometerArticle - Refereedhttp://iopscience.iop.org/1538-4357/458/1/L1/https://doi.org/10.1086/309915