The "Great Refractor" is a large telescope located at the Adler Planetarium in Chicago. Built in 1893, it features a 40-inch diameter lens, making it one of the largest refracting telescopes in the world. The telescope is primarily used for educational purposes and public outreach, allowing visitors to observe celestial objects. This historic instrument was designed by Alvan Clark & Sons, a renowned telescope manufacturer. The Great Refractor has played a significant role in astronomical research and has contributed to our understanding of the universe. Its impressive size and capabilities continue to attract astronomy enthusiasts and researchers alike.