MEASUREMENTS OF THE ANISOTROPY OF THE COSMIC BACKGROUND-RADIATION AT 0.5 SCALE NEAR THE STAR MU PEGASI

Results are presented from the third flight of the MAX experiment, an attitude-controlled balloon-borne millimeter-wave telescope with a 0.5-degrees beam, a 1-degrees chop, and a three-channel bolometric photometer. Several hours of high-quality data were obtained during a flight on 1991 June 5, including long integrations to search for CBR anisotropy, two separate measurements of dust in the Galactic plane, a brief scan of the Coma Cluster to search for the Sunyaev-Zel'dovich (SZ) effect, and a number of important systematic tests. Data from one of the long CBR integrations, carried out in a region of sky near the star Mu Pegasi, are presented. The primary structure in the data is shown to be emission from Galactic dust via its spectrum and correlation with the IRAS 100 mum map. Several approaches are used to fit this dust component and remove it from the data. An upper limit to CBR anisotropy of DELTAT/T < 2.5 x 10(-5) is obtained for a Gaussian autocorrelation function with coherence angle theta(c) = 25'. This limit is significantly higher than the measurement sensitivity of DELTAT/T almost-equal-to 1 x 10(-5) due to the presence of residual structure in the data after removal of the dust component.