Obtaining the Right Ascension, etc.

Abstract

Here the author emphasizes the importance of actual observations of the celestial objects through the measurement of their shadows etc. in determining their longitudes and latitudes. In the case of the Sun, the measurements associated with the shadow at noon and other times pose no difficulty, in principle at least, as these are done during the day. Observations pertaining to the Moon’s shadow are also possible during the night. But what about the planets and stars?