Olmsted, Denison, 1791-1859. [from old catalog] · New York, R. B. Collins · leaf 136
re 90° from the sun arecalled quadratures ; and the points half way betweenthe syzigies and quadratures are called octants. Thecircle which divides the enlightened from the unen-lightened hemisphere of the moon, is called the circle ofillumination: that which divides the hemisphere thatis turned… … that that half only which is towards the sun can be il-luminated. More or less of this side is turned towardsthe earth, according as the moon is at a greater or lesselongation from the sun. The reason of the differentphases will be best understood from a diagram. There-fore let T (Fig. 31.)…
Astronomy
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