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A TREATISE ON THE ASTROLABE
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Lyte Lowys my sone, I aperceyve wel by certeyne
evydences thyn abilite to lerne sciences touching
nombres and proporciouns and as wel considre I
thy besy praier in special to lerne the tretys of
the Astrelabie. Than for as mochel as a
philosofre saith, "he wrappith him in his frend,
that condescendith to the rightfulle praiers of
his frend," therfore have I latitude of
Oxenforde upon which, by mediacioun of this
litel tretys, I purpose to teche the a certein
nombre of conclusions aperteynyng to the same
instrument.
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Little Lewis, my son, I have prepared a lesson
on the astrolabe for you, because I see that you
are interested in science. The reasons I have
prepared my own treatise in English on the
subject are as follows
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• No one in our region of England thoroughly
  understands the astrolabe
• I have found mistakes in other manuscripts about
  the astrolabe
• Your Latin is not quite good enough to be reading
  complex material in that language, and lastly,
• You are only ten years old, and a simpler
  treatise written in plain English will help you
  understand the astrolabe better.

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My son Lewis, as a philisopher once said, he
wrappeth him in his frend, that condescendeth to
the rightful preyers of his frend, or in other
words, a good friend helps out his friend which
is what I am trying to do by giving you this
treatise.
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Dont be envious of my knowledge of science all
that I have written here is not my own work, but
compiled from other manuscripts. But considere
wel, that I ne usurpe nat to have founde this
werk of my labour of olde Astologiens, and have
hit translated in myn English only for thy
doctrine and with this swerd shal I sleen envye.
The treatise has 5 parts 1. A general
description of the astrolabe 2. How to use it 3.
Charts concerning latitude and longitude 4.
Charts concerning the movements of celestial
bodies 5. A general introduction into the theory
of astrology\
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PART I

• Here begins the description of your astrolabe
• The astrolabe has a hole in it, with which to put
  your thumb through, for measuring height, or, as
  I will from now on call it, altitude.
• The ring can also go through a chain, from which
  the astrolabe hangs down from.
• The astrolabe consists of plates piled on top of
  each other.
• A line crosses the astrolabe the upper part is
  called the south line or meridionel, and the
  lower part is called the north line or the line
  of midnight.

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5. There is also a line running down, creating a
cross like this 6. The left side is west, and
the right side is east.7. The astrolabe is
divided into 90 degrees.
8. The astrolabe is divided into the 12 zodiac
signs. 9. The astrolabe is also divided into 365
days.
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10. Next the cercle of the daies folewith the
cercle of the names of the monthes, that is to
say, Januarius, Februarius, Marcius, Aprilis,
Maius, Junius, Julius, Augustus, September,
October, November, December. The names of these
monthes were clepid thus, somme for her
propirtees and somme by statutes of lordes
Arabiens, somme by othre lordes of Rome. Eke of
these monthes, as liked to Julius Cesar and to
Cesar Augustus, somme were compouned of diverse
nombres of daies, as Julie and August. Than hath
Januarie 31 daies, Februarie 28, March 31, Aprill
30, May 31, Junius 30, Julius 31, Augustus 31,
September 30, October 31, November 30, December
31. Natheles, all though that Julius Cesar toke 2
daies out of Feverer and putte hem in his month
of Juyll, and Augustus Cesar clepid the month of
August after his name and ordeined it of 31
daies, yit truste wel that the sonne dwellith
therfore nevere the more ne lasse in oon signe
than in another.
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10-11. The astrolabe is also marked with months
of the year. These are mostly named after Lords
of Rome. Julius Caesar, for example, stole 2 days
from February, which has 28 days, to put into his
month of July. Augustus Caesar has 31 days in his
month of August, too.
Augustus
Julius
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• 12. Next to the A B C lines, there is a scale
  made up of two squares that is divided into 12
  points. The top part is called the Umbra Versa
  and the bottom part is the Umbra Recta (or
  Extensa).
• 13.The alidade (see photo) can be used to
  determine the suns position during the day or
  the stars positions at night.
• 14. A pin holds the rete and plates to the
  mater. It acts like the North Pole of the
  Astrolabe.

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• 15. The womb side of the Astrolabe into four
  quarters by a cross, just like the other side.
• 16. The womb side is divided exactly the same
  way as the other side (see number 7). Chaucer
  makes it clear that he has said this twice Now
  have I told the twyes
• 17. Under the rete, the plate is engraved with
  three circles Cancer, Aries/Libra, and
  Capricorn. These three circles or events are
  important because Cancer is the summer solstice
  Aries/Libra are the equinoxes (where the division
  between day and night are the same) and
  Capricorn which is the winter solstice.

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• 18. There are concentric circles engraved on the
  astrolabe called almuncantars (on diagram
  Altitude arcs). The zenith is the center of the
  smallest circle and should be the point directly
• above your
• head.

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• 19. Azimuths make right angles with the zeniths.
  They can be used to find the zenith of the sun or
  any other star.
• 20. Twelve divisions under the azimuths indicate
  planetary hours.
• 21. The zodiac plays an important role in using
  the astrolabe. Zodia is a Greek word meaning
  beasts in Latin. Either the sun takes on the
  characteristics of the beasts when it enters the
  signs, or the stars are arranged like the beasts,
  or the planets take on the beastly
  characteristics when they move through the signs.
  There can be other effects felt as the planets
  move through the signs (for example, if a hot
  planet moves through a hot sign or a cold planet
  moves through cold sign). Each of the twelve
  signs also governs parts of the body (Arieshead,
  Taurusthroat, Gemini arms and armpits, etc).
  

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(No Transcript)
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Form and Dates

• The Treatise is written in verse form. It
  contains an introduction and two parts in
  numbered sections. It is incomplete in that it
  was intended to contain 5 parts in total.
• The Treatise on the Astrolabe is dated to around
  1391. This makes it one of Chaucers latest
  works.

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Sources Manuscripts

• Aside from The Canterbury Tales, The Treatise on
  the Astrolabe has the most surviving manuscripts
  of Chaucers work, amounting to 34.
• The Treatise on the Astrolabe is incomplete.
• Some versions appear to have been altered
  slightly by scribes, perhaps because of a desire
  to make it more scientific and organized.
• Although the original manuscript has not been
  ascertained, the oldest versions are believed to
  have been the versions that contain many diagrams

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The Treatise on the Astrolabe is similar to The
Man of Laws Tale, because both emphasize
structure, seasons, weather, global location of
things, longitude latitude, and the concept of
time. The Treatise is very socially and
culturally relevant because it was a scientific
document written specifically for the instruction
of those not familiar with academia and was the
first known technical manual in the English
language.
Culture and social significance
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Chaucers treatise was adapted from a treatise
written by Arabian astronomer Messahala, who
wrote De Compositione et Utilitate Astrolabii in
the 8th century.
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And for the more declaracioun, lo here the
figure
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