Observatio & demonstratio cometae aetherei, qui anno 1577 et 1578 constitutus in sphaera veneris, apparvit, cum admirandis eius passionibus, varietate scilicet motus, loco, orbe, distantia à terrae centro, &c. adhibitis demonstrationibus geometricis & calculo arithmetico, cuiusmodi de alio quoquam cometa nunquam visa est

distances of the higher bodies, and what is more sublime, nor the abstruse influences of the stars, could remain hidden from them. However, their acumen did not reach the point of binding Comets to the regularity of natural laws; rather, the Comet itself, as if defiant, eluded all their skill and made their labors in vain. Yet it did not seem good to the divine goodness to completely defraud human ingenuity of this knowledge, for He deemed men worthy of such grace and light of His divinity that they can foresee and predict future positions of the stars, as is known by the argument of Eclipses, as if shown in a celestial secret council. Therefore, in the previous century, He raised up Regiomontanus, truly another Ptolemy. He taught, with wondrous sagacity, how to artificially calculate the parallaxes of Comets and, from them, to compute their true altitude from the Earth. Hence it happened that we learned to pronounce more certain things about Comets, provided they did not transcend the elemental world.

Fortified by his demonstrations, I also wished to measure the passions of this Comet and its distance from the Earth. But when I attempted this, I thought myself no less frustrated in my hope at the beginning than the ancients were. For it seemed to despise the laws of mathematics so much that I had almost despaired of inquiring about its motion, which initially appeared entirely intricate and indefinite. But after I paid more diligent attention, I perceived that its passions are far otherwise than to be detected by parallaxes according to the warnings of Regiomontanus. For he teaches how one should ascend to Comets with the aid of parallaxes. I, however, discovered through many very accurate observations that in the whole and entire daily revolution, it admitted absolutely no difference of parallax perceptible to the senses. Therefore, that calculation of Regiomontanus could not be applied to this Comet.

In the meantime, it was permitted to gather from those observations whether this Comet moved in the lower or upper world. For since it excludes all difference of parallax, it is absolutely necessary that its distance from the Earth was so great that the thickness of the Earth is hardly comparable to it, but it was exalted in many parts above the Moon.

Observation of the Comet's place. By one observation (others omitted), this can be declared more evidently. On the 2nd of December, at the 6th hour in the afternoon, the Comet was closest to the small stars in the nostrils of the Little Horse Equiculus, or Equuleus, distant from the more westerly one toward the south, and partly declining toward the west, by a third of the space that lies between those two stars, forming almost a right angle with them. But after an accurate examination, of which more below in chapter 6, I found its place to be at 17 degrees 17 minutes of Aries ♈, with latitude 24 degrees 46 minutes north. For the place of this star is 17 degrees 22 minutes of Aries, latitude 25 degrees 10 minutes north, as will be said below. On the same night, at the 9th hour, I sought its place again, which I found to be at 17 degrees 25 minutes of Aries, with latitude 24 degrees 47 minutes north approximately. The place of the Comet was therefore further behind, closer to the said star than before: for it was made by such a portion.