This study demonstrates the use of the latest thermal analysis software in determining the primary mirror temperature gradients in a telescope tube with varying L/D, tube temperature, and mirror materials. It extends previous thermal radiation analysis work to include radial conduction in the mirror. Tube ID is fixed at 24'. Tube length varies as follows: 20', 40', 60', 100', and 200'. The focal length assumed for the parabolic mirror is the tube length. 1/2 tube length and flat mirror were also tried. The mirror material/thickness is varied as follows: ULE - 21/2' thick, QFS - lightweighted - 1/2' thick, aluminum - 21/2' thick. Space temperature is fixed at 3 K. The tube temperature is fixed at five values, 300 K, 250 K, 200 K, 150 K, 100 K, and 50 K. The mirror coating is Denton Ag, with an IR emissivity of 0.035. The tube inside surface coating is diffuse black, with an IR emissivity of 0.9. The mirror is assumed to be conductively isolated from the tube. The outside of the tube and the back of the mirror are adiabatic. The mirror is simply in thermal equilibrium with the fixed temperature tube and space.