We report the results of testing samples made of glass ceramics with a zero thermal expansion coefficient. The samples consist of two parts, joined by a new technology of solid-phase sintering polished parts with vacuum-deposited aluminum coating of nanosized thickness. Also reported are data on the stability of these samples after exposure to extreme factors such as cryogenic temperature (temperature of liquid nitrogen), high temperatures of 400 and 1000°C, laser radiation, etc. The test results show that the suggested technology can be used for producing light-weight astronomical telescope mirrors of Zerodur glass ceramics. In our opinion, the suggested design of a light-weight astronomical telescope mirror with two parts joined by the new technology [the bottom part is silicon carbide (SiC) and the upper is an optical layer of glass ceramics with a thermal expansion close to that of SiC in value] is promising.