APIAN TO THE READER

Ornamental drop cap 'Q' with a figure holding a staff or instrument.WHEN WE OBSERVED, DEAREST
Reader, that many distinguished and most eager minds for the astronomical art exist everywhere in this our age, but that upon approaching its study, they are immediately turned away—indeed, driven quite into flight—by the sheer abundance of numbers, the difficulty of calculation, and the sharpness of speculation; and that consequently, while countless men are found highly learned in other disciplines, very few are found even slightly skilled in this most free art, we could not help but grieve from the heart. But tell me, I pray, what is the cause of this? Truly none other than that in their early years, boys are taught arithmetic rather poorly, without which neither astronomy nor the other sciences can be rightly learned. For the knowledge of number not only serves the science of the stars, but prepares the minds of men for every other study and renders them more fit, so that Pythagoras did not speak rashly when he said that he who knows numbers knows all. When we saw this, I say, and noticed that mathematics drew such hatred upon itself in the name of difficulty, we began to think by what means a remedy might be found for this blemish, and how aid might be brought to those whom, though arithmetic has deserted them, astronomy might at least not repudiate. Thinking for a long time: at last, it occurred to us that if the entire theory of the heavens could be reduced to instruments without numbers and calculations, it might be possible. The task seemed a truly daunting face, and one which the mind could scarcely sustain in thought at first, unless it should set aside its harshness over time and offer itself as more manageable after long cultivation. Therefore, since it promised some hope of still being pursued, we (striving with God as our leader, although nothing of this kind had been dreamed of by any mathematician until now, let alone attempted in work) discovered how anyone, under our guidance, could investigate the courses of the stars, the motions of the wandering planets, the reasons for eclipses, and the contemplations of other celestial matters, faster than it can be told, through instruments without any labors of calculating. Meanwhile, during the labor, we were more than once discouraged by those who dared to ask why we, so insane, would enter upon a path so tangled, so unready, touched by no tracks at all, no path, and no feet. Indeed, when the matter appeared superior to every effort for some time, terrified partly by the difficulty of the thing and astonished partly by its novelty, we retreated more than once; we confess we would not have progressed even a little—however much Hesiod An ancient Greek poet. sang to us that virtue is placed on a steep height, and Virgil Original: "Maro," the family name of the Roman poet Virgil. that tireless labor conquers all—unless we knew that the greatest fruit would soon answer the greatest labor: namely, your benefit, whoever you may be. While we looked toward this, we could easily forget the entire burden. For divine instruction, besides Plato, had already taught me long ago that I was born for you. Because you, in turn, will also weigh this and truly persuade yourself that I have consulted your interest, I do not doubt that you will interpret our work in the best possible light. It remains that I would not wish you to be ignorant that the structure of the entire work or the instruments have been illustrated through the birth charts Original: "genituras," meaning horoscopes or astrological charts at birth. of the Roman Emperors CHARLES and FERDINAND, yet in such a way that the times as they are cited are by no means exactly so; for only the days and years can be recognized in these, but as far as hours and minutes are concerned, not at all. I have introduced these examples of motion for a double reason: partly because I saw a need for some demonstration, without which it was in a way useless to propose the bare use of the instruments; and partly because no other demonstrations occurred to me which were worthier to commit to posterity. In these, therefore, if nothing else is remembered, at least the day and year—which everyone sees is the only thing truly worth remembering for eternal posterity—will be read as certain and true. How much we have sweated in this work of demonstrating, you estimate, fair reader, while we have watched over your utility
indefatigably.
For you ought to
think that whatever
labor this is, it was
undertaken in
your name.
If you do
this, you will compel
me one day, with
God’s help, to produce
a certain special work
on eclipses, just as
you will be able to
hope for the tables,
which they call "resolved,"
to come to you shortly
by a more ready and
concise way, if you
favor our effort.
Farewell.

IN WHICH ALL THINGS

WORTHY OF KNOWLEDGE

contained in this work are visible to the

eyes, set forth in alphabetical order.

Small decorative woodcut of a flower or plant.

A Years from Adam to Christ according to Alfonso, Eusebius, Albumazar, and the Hebrews. Statement 1 The "Statement" numbers refer to the numbered propositions or sections in the text.
When the reign of Artaxerxes, called Ahasuerus, occurred. Statement 1
When Aristotle existed. Statement 1
How many years the death of Alexander preceded Christ. Statement 1
In what age Aratus the poet and astronomer wrote. Statement 1
The age of Archimedes’ geometry. Statement 1
When Abrachis Likely referring to Hipparchus. the astronomer lived. Statement 1
When Andromachus of Crete, inventor of Theory, flourished. Statement 1
When Agrias the astronomer observed the stars. Statement 1
When Alcmaeon the physician and astronomer flourished. Statement 1
The age of Albategni Al-Battani, a famous Arab astronomer. the Mathematician. Statement 1
The century of Azophi Al-Sufi. the Arab. Statement 1
The time of Avicenna the physician. Statement 1
The century of Abraham Ibn Ezra the Jew. Statement 1
The age of Alfonso, King of the Romans and Spain, and most famous astronomer. Statement 1
The invention of the art of printing, by whom and when it was done. Statement 1
What the Solar Year is. Statement 1
The Leap Year. Statement 1
The Intercalary Year. Statement 1
What the Civil Year is. Statement 1
The Lunar Year. Statement 1
Various differences of years. Statement 1
Days are computed by astronomers from noon to noon. Statement 1
The error of astronomers computing the years preceding Christ through the "root of Christ." Statement 1
Where the beginning of Aries is situated on the true ecliptic. Statement 2
The point of the equinox varies repeatedly in the equator, and therefore the times themselves. Statement 3
When the vernal equinox occurred in the time of Christ. Statement 2
When the vernal equinox occurs in our age. Statement 2
What shadow the day of the equinox describes. Statement 2
The equinox at the time of the founding of the city Rome.. Statement 13
At what times the equinoxes happen. Statement 39
To adapt the equinoxes to all meridians. Statement 39
The abominable error of some regarding the vernal equinox. Statement 2
How the apogees Original: "auges," the points where planets are furthest from Earth. of the planets before and after the times of Christ are known. Statement 4
The apogees of the wandering stars at the time of the flood. Statement 4
The apogees of the planets in the times of the Emperors Charles and Ferdinand. Statement 4
Auriga The Charioteer constellation. marked by various names. Statement 4
The form of the celestial Eagle Aquila.. Statement 4
The figure of Andromeda placed in the sky. Statement 4
How the southern stars set with the Sun sooner than they rise. Statement 4
From where the Atlantides or Pleiades are named, and how many they are. Statement 4
Where the stars of the Asses Aselli, in the constellation Cancer. are located. Statement 4
The situation of the ship Argo. Statement 4
How to find the argument of lunar latitude. Statement 18
What an Aspect A specific angular distance between planets in astrology/astronomy. is and what is to be understood by it. Statement 19
What the number of Aspects is. Statement 19
How to attain any Aspects of the Moon with all the planets through calculations. Statement 20
By what reasoning you may grasp the Aspects of the planets among themselves, excluding the Moon. Statement 21
How to find the Aspects of the planets among themselves, besides the Moon, through numbers. Statement 21
When a planet is said to "apply" An astrological term for one planet moving toward an aspect with another.. Statement 21
How the mean argument of the Sun is obtained. Statement 25
In what way the mean argument of the Moon is investigated. Statement 25
When Anaxagoras began to write about the motion of the Moon. In the example. Statement 30
How the Athenians adapted the numbers of their months to the ages of the Moon. In the example. Statement 30
How the Golden Number is found. Statement 35
The invention of the Golden Number. Statement 35
The use of the Golden Number. Statement 35
Why the Golden Number was neglected by later people. Statement 35
The Golden Number in the time of Julius Caesar. Statement 35
The inquiry into the leap year. Statement 37
How many days the Solar Year consists of according to Julius Caesar. Statement 37
How the stars are instruments of divine virtue. Statement 49
That all lower things are affected by the dispositions of the stars. Statement 40
What the entry of the Arcalis Meteoroscope is. Statement 1 of the second part.
Low.