3. On the Accuracy attainable by means of Multiplied Observations

Extract

On opening any astronomical work of the present day, we are at first startled by, and then familiarized with, the excessive precision of the numbers set down. In our Nautical Almanac, for example, although referring to a period three or four years subsequent to the date of publication, the declinations of the stars and planets are set down to tenths of a second of arc, and their right ascensions to hundredths of a second of time.