Alvan Graham Clark was an American astronomer born in 1809. He is best known for his work at the University of Michigan, where he contributed significantly to the field of astronomy. Clark was particularly noted for his advancements in telescope design and construction, which improved the quality of astronomical observations. In 1861, Clark discovered the moon of Mars named Phobos, although he did not receive widespread recognition for this achievement at the time. His contributions to the development of optical instruments helped pave the way for future discoveries in astronomy, influencing the work of later astronomers and scientists.