Ptolemys Tetrabiblos - Book 2: Ch. 10
CHAPTER X

COLOURS IN ECLIPSES; COMETS, AND SIMILAR PHENOMENA

IN investigating general events, it is necessary further to observe the colours or hues displayed during an eclipse, either in the luminaries, or around them; in the shape of rods or rays, or in other similar forms. For, if these colours or hues should be black, or greenish, they portend effects similar to those produced by Saturn's nature; if white, to those operated by Jupiter; if reddish, to those by Mars; if yellow, to those by Venus; and if of various colours, to those by Mercury.

And, if the entire bodies of the luminaries be thus coloured, or should the hues extend over all the parts immediately circumjacent to the luminaries, it is an indication that the effects will attach to most parts of the region, or countries, with which the eclipse and its ruling places may be in familiarity. If, however, the colouring should not spread over the whole surface of the luminaries, nor over all the parts around them, but be limited to some particular quarter, then only such a portion of the said countries, as may be indicated by the situation of the visible hues, will be comprehended in the event.

It is also requisite to notice, with respect to general events, the risings or first appearances of those celestial phenomena called comets, whether presenting themselves at ecliptical times or at any other periods. They are displayed in the shape of beams, trumpets, pipes, and in other similar figures, and operate effects like those of Mars and Mercury; exciting wars, heated and turbulent dispositions in the atmosphere, and in the constitutions of men, with all their evil consequences. The parts of the zodiac  in which they may be posited when they first appear, and the direction and inclination of their trains, point out the regions or places liable to be affected by the events which they threaten; and the form of the signs indicates the quality and nature of those events, as well as the genus, class, or kind, on which the effect will fall. The time of their continuance shows the duration of their effect; and their position, with regard to the Sun, the period when it will commence; as, if they first appear matutine, they denote an early commencement; but, if vespertine, that it will be late and tardy.

The general and more comprehensive parts of the consideration regarding regions, countries, and cities, having now been explained, it becomes necessary to discuss certain particular points of the same consideration; that is to say, the annual occurrences which take place at certain fixed seasons, and the chief of which is that called the New Moon of the Year.