Announcements
•First exam is three weeks from today (February
18). Will cover chapters 1, 2, 3, 4 & 5. Sample
questions have been posted. Format will be 15
MC’s (3 points each) and 3 essays (18 points
each) from a list of 5
•Dark Sky Observing Night Tuesday night. Set-up
starts 45 minutes before the start time so meet
here at 6:45pm. Cancellation notice, if needed, will
be posted on APSU Astronomy website by 5:00
that day.
•Start Chapter 4 for next time. Think of some
discussion questions to bring to class
Islamic Astronomy
Much of the “science” went on in
the “House of Wisdom”
Established in
Bagdad in the
late 8th Century
as a center for
translations.
Eventually
becomes the
Islamic
equivalent of
the Library of
Alexandria
The
Islamic
Calendar
is a lunar
calendar
Months are 29 or 30 days. The
year is 354 days long.
Each month would only begin
with the sighting of the Waxing
Crescent Moon
Eventually, calculations are made
to assist in the observations
Early calculations resulted in tables of “visibility” for each
latitude and some longitudes
Prayer Times required means of
telling the time
Early on “folklore” astronomy was
used. Some used sand clocks or
hour glass “clocks” to determine
the times. Eventually, muwaqqit’s,
official time keepers are
appointed for each mosque.
al-Khwarizmi
was the first
to produce
prayer time
tables
His tables were for
Bagdad but modern
prayer tables can
be found for any
location on Earth
Also important was the direction to Mecca
Not only should you pray towards Mecca, mosques and other
structures should be aligned to Mecca
The Qibla Compass allows you to
find the direction to Mecca
Mecca-Centered world maps
were generated as an aid
Islamic Observatories tended to not
survive very long
Taqi al-Din at his
observatory in
Istambul
The Maragha Observatory in Iran
The Observatory of Ulugh Beg was
the most elaborate
The chief observer was Ulugh
Beg, the governor and then
Sultan of Timur (current day
Uzbekistan, Tajikistan,
Turkmenistan, Kyrgyzstan and
Kazakhstan
The quadrant was over 130
feet long and still survives
today
After Ulugh’s Death ,most of the
observatory was destroyed
The Islamic astronomers especially
didn’t like Ptolemy’s equant
The solution:
add epicycles
to the epicycle
The Astrolabe
The astrolabe is a combination planisphere and time
keeper. It allows you to determine the time given your
location and the visible stars. It can also compute the
position of the Sun or Moon
The Astrolabe in pieces
Check out the
Astrolabe
website
An Islamic astrolabe with calendar
Islamic Astronomy
began to fall
behind after the
invention of the
telescope