Alvan Graham Clark

Alvan Graham Clark (July 10, 1832 – June 9, 1897), born in Fall River, Massachusetts, was an American astronomer and telescope-maker. He was the son of Alvan Clark. In 1862, while testing a new 18-inch refracting telescope he discovered Sirius B, the magnitude 8 companion of Sirius.

Reference

• http://reference.allrefer.com/encyclopedia/C/Clark-Al.html