Reflector telescope

Since all of these designs rely extensively on mirrors, it is particularly important to choose appropriate mirror materials. Mirror materials mainly include glass materials, low expansion metals, and ceramics. Glass materials have low thermal expansion coefficients and excellent optical properties, but their thermal conductivity and specific stiffness are poor. Metal materials have excellent thermal conductivity, but their thermal expansion coefficients are relatively large, and their surface shape accuracy is easily affected by temperature. Metal mirrors do have the advantage of high melting point, high hardness, high wear resistance, and oxidation resistance.

What is a Silicon Carbide Reflective Telescope?

If metal and glass both have significant downsides, what is the material of choice for large-format modern reflective telescopes? A modern material that has nearly ideal mechanical and physical properties: silicon carbide. Silicon carbide is a lightweight, stable compound produced by the reaction of carbon and silicon at high temperatures. When sintered or heat treated, these elements react to form a structure with ceramic characteristics. 

Silicon carbide reflective telescopes, based on silicon carbide mirrors, are built to take advantage of the many advantages of this modern substrate. Lightweight, durable, and with good radiation resistance, these telescopes are pushing the boundaries of astronomical research worldwide.

One example of a silicon carbide reflector telescope is the 4m Daniel K. Inouye Solar Telescope (DKIST), formerly known as the Advanced Technology Solar Telescope. This Gregory reflective telescope was designed to study solar magnetism and the solar winds and flares controlled by it, and utilizes a 4.24 meter primary mirror to do so. The secondary silicon carbide mirror has dimensions of 0.65 m, and the telescope has adaptive optics meant to correct for atmospheric distortions. 

The LORRI (Long Range Reconnaissance Imager) on board the New Horizons spacecraft is another silicon carbide reflecting telescope. The design of telescope is Ritchey–Chrétien, a specialized type of Cassegrain reflector, and it features a main  silicon carbide mirror with a diameter of 208 mm. The effective focal length of the telescope is 2630 mmm, and  the imaging system can take pictures at very low light. It hs been used to successfully take high resolution images of Jupiter, Pluto, Arookoth, and the moons of Jupiter and Pluto.