Anisotropy in the cosmic microwave background at degree angular scales: Python']Python V results

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37 to 45 GHz in two frequency bands. With a 0.degrees 91 x 1.degrees 02 beam, the instrument fully sampled 598 deg(2) of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l similar to 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l similar to 40) to small (l similar to 200) angular scales. The shape of the observed power spectrum is not a simple linear rise, but has a sharply increasing slope starting at l similar to 150.