This article summarizes how the radio sky background will appear using antennas of different beam sizes, and how it varies with frequency. If you want to know the sky background temperature in a given direction, you have to specify the beam size. The 2 figures below illustrate how the sky looks in RA-dec coordinates with a 10-degree beam, and a 40-degree beam. The contour levels are the same in both figures, with intensities of 40 K or more shown dashed.