Anna Winlock asked to become a computer for the Harvard Observatory in 1875 and was hired to work for 25 cents an hour. By 1880, Edward Charles Pickering had hired several women to work for him at Harvard because he knew that women could do the job as well as men and he could ask them to volunteer or work for less pay. The women, described as "Pickering's harem" and also as the Harvard Computers, performed clerical work that the male employees and scholars considered to be tedious at a fraction of the cost of hiring a man. The women working for Pickering cataloged around ten thousand stars, discovered the Horsehead Nebula and developed the system to describe stars. One of the "computers," Annie Jump Cannon, could classify stars at a rate of three stars per minute. The work for Pickering became so popular that women volunteered to work for free even when the computers were being paid. Even though they performed an important role, the Harvard Computers were paid less than factory workers.