Ever since the introduction of the first telescope 350 years ago, it was realized that with an increase in the size of the instrumebts there would be a corresponding increase in the depth to which they could penetrate into space. After the work of lord rosse in the eighteenth century and herschel in the nineteenth century, who built telescopes of increasing sixe and power in britain, it was in america that the great advances in this field occurred in the twentieth cenury