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

Just as I am uncertain about the first day of appearance because of the inclemency of the air, so the same did not allow me to observe the certain day of its extinction. For on the 8th of January of the current year '78, I clearly observed that it had not yet vanished, although it certainly shone with a dim and obscure radiance; nevertheless, it was not difficult for me to note its place under the starry sphere. But from that day, heavy rains hid the Comet from my eyes along with other stars. On the 14th, the air shone a little less obscurely, but no remains of the Comet were discerned; although, if any had remained, they could hardly have been perceived by sight, having made a comparison to the observations of the 3rd, 5th, 6th, and 8th of January, so that they could easily have hidden under the light of the Moon, which was almost half-full and near, or been covered by thick vapors in the air remaining after the rains. But on the 18th of the same (in the meantime the sky was filled with clouds again) and on the following days, no trace of it appeared anywhere. It was therefore seen by me for 58 days, namely from the 12th of November until the 8th of January.

A probable conjecture about the first rising and last extinction of this Comet. Chapter 9.

But if conjectures, leaning upon probable reason, about the first rising of this Comet and also its exhaustion had any weight, I, having taken an argument from its most orderly motion (as will be said below), would entirely believe that it was first ignited under or before the morning dawn on the 5th of November, and did not completely fail before the evening of the 10th of January, so that the time of its duration was about 66 and a half days. Although, indeed, it is difficult to determine anything certain in an uncertain and doubtful matter, yet in what follows it will be proved that this conjecture agrees most beautifully with observations and experience in elegant harmony.

Furthermore, it must not be passed over here that it has been reported to me that the radiance of this Comet was revealed somewhere as early as October; to which rumor also adheres Leonhard Thurneisser, the Physician, in a writing published about this Comet, who asserts that he first noted it in the sky at Berlin on the 19th of October. He reports, moreover, that the Comet then stood in the loins or thighs of Sagittarius, from which it retreated, and began to move against the order of the signs through the places I also noted above. But since truth in these passions of this admirable divine work, which I have presumed to investigate with God's favor, must be followed by me no less than in any other matters, necessity seems to demand that I commemorate my observations, which I held diligent on those very days, so that from them it may become clear which opinion agrees with the truth. Moreover, on that same day, the 19th of October, I observed the position of Saturn next to the stars in the head of Sagittarius, which I found to differ from the calculation of the Prutenic tables by almost half a degree in longitude and a whole third in latitude.