The Emperor's Astronomy

ASTRONOMY OF THE CAESARS

Betelgeuse original: "Algeutze" sets on April 25. On the first of July, it rises again with the Sun. Next follow three stars, gathered almost in a single line, of the second magnitude, forming Orion’s Belt, which the common people call Saint Jacob’s Staff. The first of these sets on May 6, having been visible for eight hours after nightfall; the second on the 7th; and the third on the 8th of the same month. On June 27, the first rises again; the second on the 28th; and the third on the 29th. Furthermore, there is a star of the second magnitude in the left shoulder called Bellatrix; it sets on May 9 and rises on June 19. The right shoulder of Orion is called Betelgeuse original: "Beldalgeuze" by the Arabs, in which is a star of the first magnitude; it sets on May 16 and rises on June 25. Besides these, the misty star of the head is specially observed here, which sets on May 11 and climbs the horizon again on June 23. After these, nine stars of the "shroud" original: "sudarioli," likely referring to the lion's skin or cloak Orion holds—otherwise called the "ox-hide"—are numbered, which the left hand holds up. Because these hold only the 3rd and 4th place of brightness, I pass over them. Finally, the right hand carries a certain club, which likewise contains two stars.

Eridanus.

*The figure of Eridanus The River is fashioned from thirty-four stars, with two being quite bright: one of the first and another of the second clarity. There is also a third star common to both Eridanus and Orion, which occupies the beginning of Eridanus and the left foot of Orion (of which I spoke before); the remaining stars, being beyond the third magnitude, claim nothing special for themselves. Eridanus is otherwise called the Po, the Gihon, or the Nile, and also the Ocean. The star inserted into the curve of Eridanus, called Angetenar in Arabic, sets on March 17 and rises on June 15. The star at the end of Eridanus, holding the first place of light and named Achernar, hides on February 15 and rises on July 28.

The Hare.

*The Hare Lepus consists of 12 stars, none exceeding the third degree of clarity. The four stars sitting on the ears of the hare, two on each, set on April 22 and emerge again on July 6.

The Great Dog.

*The Lesser Dog Canicula, the Great Dog, or the Second Dog are all the same, encompassing 18 stars and 11 unformed stars. One star is the most brilliant of all the fixed stars, called Alhabor in Arabic, a very common name. It is also called Sirius, Syrion, Aschere, or Aliemeni. Upon its rising, the solar heat is increased and multiplied, so much so that the earth is, as it were, scorched, and dogs are driven to madness. In our climate, it sets around May 8. It rises again with the Sun on July 26, at roughly the 12th degree of Leo—that is, around the feast of Saint James, which is likewise the beginning of the

The Dog Days.

Dog Days. However, the beginning of these days changes occasionally according to the diversity of regions and climates. In the age of Hippocrates, who lived in the fourth climate nearly 400 years before the birth of Christ, that beginning occurred on July 13 or 14. Under Avicenna, who lived in the same fourth climate 1100 years after Christ, this began in a certain way on July 15 or 16. Now our own age, subject to the seventh climate, experiences it on July 15 and 16, at which time the Dog Star also rises at dawn original: "Cosmicè," occurring at sunrise. It first appears around the 9th day of August; thereafter it is continually more visible before the rising of the Sun, which appearance gradually brings the Dog Days to an end.

The Lesser Dog.

*Procyon, which bears the name of the Lesser Dog, displays only two stars; it is also called the First Dog and the Fore-dog original: "praecanis", because it precedes the others in its rising. To the Arabs it is Aschere, Algomeisa, or Ascemie. Pliny wishes this to be the Canicula. We, however, following the ancients, call it Prokyon original: "πρόκυων," Greek for 'before the dog', that is, the Fore-dog. It begins to be obscured in the evening on May 19, and truly sets after the 7th day of June; finally, on July 16, it rises precisely with the Sun, and on July 31 it moves away from the Sun—that is, it rises heliacally and is seen in the east.

The Ship.

*The Ship is called Argo, Jason’s Ship, the Argonavis, and by some Noah’s Ark. This encompasses 45 stars. Three are more prominent, one of which is of the first magnitude, located in the Oar; in our climate, it is always hidden, and for that reason, I have not included it on this map. Indeed, by reason of latitude, it would have required a much larger map. It is called Canopus, Inmora (that is, the horse), or Subhel and Suhel by the Arabs. Besides this Canopus, there are still 4 stars of the second magnitude in the Ship.

The Hydra.

*The Hydra, the Water Snake, the Serpent, or the Great-Souled Serpent as called by more recent authors. It is composed of 25 stars, none superior to the third magnitude, except for one which shines in the second and is called Alphard of the Hydra (that is, the "bright one" of the Hydra). Its cosmic setting setting as the sun rises occurs on June 24, and its rising on August 15. There are also two unformed stars standing nearby.

The Cup.

*The Cup Crater follows (although some make the Cup, the Raven, and the Hydra into a single image), which is also called the Vessel or the Bowl; it is made of 7 stars, all of the fourth magnitude. The first is common to the Hydra and the Cup, called the base or bottom of the vessel. This sets on July 5 and rises on September 11.

The Raven.

*The Raven Corvus has 7 stars no larger than the third degree of brightness, of which the one in the right wing, called Algorab in Arabic, is endowed with the third magnitude. Its setting with the Sun happens on August 4, and its rising with the same on September 25.

The Centaur.

*The Centaur possesses 37 stars. Of these, six are bright: 5 of the second magnitude and one of the first. The right shoulder-blade of the Centaur withdraws on July 26 and emerges again on November 7.

The Wolf.

*The Wolf, the Wild Beast, the Small Beast, or the Beast therion original: "θηρίον," Greek for beast, consists of 19 stars of the 3rd, 4th, and 5th luminosity. But since there is nothing here worthy of note, I shall refrain from saying more.

The Censer.

*By a more frequent and better-known name, they call the Censer the Ara or the Altar; also the Sanctuary, the Hearth-god, the Temple, the Well, and the Fireplace. 7 stars constitute it: two of the fifth light, the rest of the fourth.

The Southern Crown.

*There is also the Southern Crown, which is called the Notian Crown, the Austral Crown, or in Greek stephane notia original: "стеφάνη νότια," the Southern Wreath (that is, a little heaven), and by others Ixion's Wheel. Since its stars do not exceed the fourth order of magnitude, I shall pass over it.

The Southern Fish.

*The Southern Fish Pisces Notius is the last; it is called the meridian, or the great southern fish likewise. It carries 11 stars of the fourth and fifth degree of luminosity. Of these, the one in the back sets on January 16 and rises on March 21.

Briefly, therefore, the sum of the southern stars is 316: seven distinguished by the first luminosity, 18 by the second, 63 by the third, 164 by the fourth, 54 by the fifth, and 9 by the sixth. There is one misty star. Indeed, the total number of all stars of the eighth sphere now enumerated in order, both greater and smaller, is 1022. Thus, you have the complete treatment regarding the fixed stars.

THE FIFTH PROPOSITION

Causes of the diversity of natural days.

Since NATURAL DAYS are numbered from noon to noon—specifically, from the moment the Sun touches the meridian, at which point it is midday—this occurs in as much time as the Equinoctial circle encompasses the whole earth, and a little more. That is, by as much a portion of the equinoctial corresponding to the zodiac in which the Sun moves, as the whole equator revolves. That portion of the equinoctial addition will be called by us hereafter the "additament." Because this addition is not equal every day, it follows necessarily that these days must become dissimilar; thus, natural days are also unsuitable for finding the motions of the stars. This diversity of days happens for two reasons: One, because while the Sun completes a uniform motion in its eccentric circle, it cannot describe equal arcs in the zodiac at the same times. The other, because however much the arcs of the Zodiac are equal so that they are not, as was said, designated daily by the sun, nevertheless, because of the obliquity and the measurement of the declinations, the ascensions or additions of the equator are not similar. Therefore, natural days, which are computed from one noon to the next, disagree with themselves in quantity. For the same reason,

Differing and apparent days.

they contribute nothing to the investigation of aspects and the finding of the courses of the planets. These days are also called "apparent" and "differing" days. Therefore, to investigate the movements of the stars accurately, there was a need for "parity" or "mean" days. Even though the difference between a natural day and an equal day might seem to be almost nothing, when many are collected together, a sensible difference in time is produced, which must not be neglected in the faster movements, especially those of the moon and its aspects. To satisfy the second part of this theorem, an instrument follows, which has been useful for some hundreds of years. Its outermost circumference represents the days of the year, while the inner part represents the minutes of the equation. Its beginning is near the first day of February, marked with the letter B. From B on both sides, black and white colored degrees occur, each of which contains ten seconds of time; every sixth degree is marked with a zero, noting a minute of time, so that from B to L on the right, there are 20 minutes. From L to E, each degree indicates 2 seconds, but from 10 seconds up to the letter L, each division notes 1 second. The same logic applies from M to E. Furthermore, for one counting from B to the left, each degree yields 10 seconds; the zero with its lines signifies minutes, up to O which encompasses 32 minutes; from O to C, any section is 10 seconds. Similarly from N to C, except that the nearest degree on both sides at C holds 8 seconds more than 32 minutes. It is also the case that each degree between the letters F to G refers to one second, the beginning of which is D with 52 seconds—that is, beyond 11 minutes. For with the thread falling precisely over the letter D, the equation of days will be 11 minutes and 52 seconds. Then you will find the remaining seconds up to 60 (that is, 12 minutes) near F and G.

Use of the instrument.

The use of the instrument is as follows. If you require the courses of the faster planets (for the slower ones do not need it) for a certain day, first seek the day you have appointed inscribed on the outermost circle. Apply the thread hanging from the center to it, while at the same time noting the minutes and seconds

Equation of time, ready for both subtraction and addition, in conjunctions and aspects.

on the inner circle touched by the thread. Subtract these from your time, and then the days and hours will be equated, with which it will be possible to investigate the motions, as you will hear below. In conjunctions and aspects, however, the logic is different: where (as you will learn in what follows) you find the day, hour, or minute of any aspect, the aspect will still be said to be in "unequated days." When, through the time found, the minutes and seconds of the equation are first sought in the instrument, they must be added to the unequated time, and then the aspect will come forth in equated days.

Example of CHARLES.

The matter will be made clear by an example. Suppose the birth of the Emperor CHARLES Charles V, Holy Roman Emperor to be on the 23rd day of February at 15 hours and 44 minutes, for which you wish to know the planetary courses accurately. With the day sought and the thread fitted to it, 2 minutes and 56 seconds are seen to be cut by the thread in the inner part of the circle. When you subtract these from the birth time, there result 23 equated days, 15 hours, 41 minutes, and 4 seconds.

Example of FERDINAND.

Another: King FERDINAND Ferdinand I, brother of Charles V was born on the 10th day of March, though not in the same year; therefore his equation will be 7 minutes and 30 seconds. You will take that from the time of birth, namely 20 hours and 47 minutes; there will remain 20 hours, 39 minutes, and 30 seconds. And this will be called the equated time of King Ferdinand. But if on that same day of birth a conjunction or aspect had occurred at a certain hour and minute, these 7 minutes and 30 seconds would now have to be added. And thus the time of that conjunction or aspect could be said to be in equated days.