The optics and detectors of a solar telescope are similar to telescopes that are used primarily at night. What is different is that solar telescopes must be constructed to account for the intense brightness and heat they experience. One way to keep the telescope components and instruments cooler is to direct the light into an underground chamber first. Another way is to maintain a vacuum around the telescope, because in a vacuum no air molecules are present to absorb and transfer the heat. Whereas most nighttime telescopes are designed to have as large a primary mirror as possible, but otherwise be light and maneuverable, the primary mirrors of solar telescopes are not particularly large—the Sun is, after all, close by and very bright! The equipment and building structures associated with solar telescopes, though, are often huge.