  We present a detailed thermal and structural analysis of a 2m class solar
telescope mirror which is subjected to a varying heat load at an observatory
site. A 3-dimensional heat transfer model of the mirror takes into account the
heating caused by a smooth and gradual increase of the solar flux during the
day-time observations and cooling resulting from the exponentially decaying
ambient temperature at night. The thermal and structural response of two
competing materials for optical telescopes, namely Silicon Carbide -best known
for excellent heat conductivity and Zerodur -preferred for its extremely low
coefficient of thermal expansion, is investigated in detail. The insight gained
from these simulations will provide a valuable input for devising an efficient
and stable thermal control system for the primary mirror.
