Changes in weather conditions, such as passing clouds, haze, or too sunny etc., result with fluctuation in solar radiation entering a solar reactor. This creates a major problem in solar reactor efficiency. Because: solar reactors must be operated at certain temperatures depending on the required dissociation temperature of the feedstock. For example, natural gas cracking solar reactors require temperatures of about 1500K to produce hydrogen and carbon. Fluctuation in solar radiation due to weather changes creates temperature fluctuation inside the solar reactor preventing from maintaining constant or semi-constant production rate. In this paper, we present our most recent research results toward solving this problem by designing, manufacturing, and testing a camera-like aperture mechanism. With this mechanism, it is possible to achieve semi-constant temperatures inside the solar reactor by adjusting the solar reactor itself against changes in the incoming solar radiation. Results show that when the incoming solar radiation is 5kW, the aperture radius should be 1.8cm to have reactor temperature at 2100K. However, to keep this temperature when the incoming radiation is 7kW, the aperture radius should be 3.2cm. It should be also noted that at lower temperatures, optimum aperture radius converges to one value, which is about 4.7cm.