Sentence:  Who can discern those planets that are oft <WSD>"Combust</WSD>", and those stars of brightest magnitude that rise and set with the Sun, untill the opposite motion of their orbs bring them to such a place in the firmament, where they may be seen evning or morning. 
Meaning of the word marked with <WSD> tags:  In close conjunction with the sun (so that its astrological influence is "burnt up"), sometimes specified to be within 8 degrees 30'.