Caroline packed up the household and moved it to Windsor. When King George wanted them closer still, she moved again. This time they moved to the tiny town of Slough, north of Windsor. Here the Herschels turned their house into the foremost astronomical observatory of their time.

   Every clear night, Caroline and William studied the heavens. He sat high above the house at a telescope. She sat below in a small, unheated room beside an open window so she could hear him. As William called out the position of each star, comet, or nebula, Caroline checked the star charts and recorded the information. A metronome ticked away at her side, keeping track of the time of passage of each object.

   A visitor to the Herschel home wrote in his diary about an evening when the temperature dropped to twelve degrees Fahrenheit. The Herschels just put on more clothes. When Caroline’s ink froze, she melted it over her candle and went on writing.

   On nights they observed, she worked all night long and slept just a few hours in the early morning. During the day, she copied William’s papers for publication and checked his computations. She wrote the directions for assembling the telescopes they sold, and designed and published the star catalogs.

   Their telescopes grew larger along with Caroline’s catalogs. They made huge polished-metal mirrors to gather and reflect light from distant stars. For their largest, a forty-eight-inch mirror, they melted many pounds of molten metal. They poured the liquid metal into a mold formed in a huge mound of soil and sand in the backyard. After casting, they polished the mirrors to a high gloss by hand. William polished the mirror for days at a time, and Caroline spooned food into his mouth as he worked.

   When they mounted the big mirror in a forty-foot-long tube, it became the largest telescope in the world. It was often called the eighth wonder of the world, and travelers came to Slough from all over the world to see it.

   As William and Caroline’s reputations grew, astronomers from around the world visited the Herschel home to exchange ideas and information. William also visited other astronomers, both in England and Europe. Caroline enjoyed meeting and talking with visiting scientists in her own home, but she hated travel and seldom left Slough. She had little patience with tourists who came to see the sights without any interest in astronomy, even members of the royal court. In her diary, she referred to one lady-in-waiting as a “giggling ninny.”

   Caroline’s life settled into a peaceful routine. But William had another surprise for her. In 1788, he married Mary Pitt, a widow who lived nearby. The marriage came as a shock to Caroline. Another woman now held first place in William’s affections, and Caroline worried again about money. Where would she live? What would she eat? How could she clothe herself?