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

tablesHis 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

IstambulThe Maragha Observatory in Iran

The Observatory of Ulugh Beg was the most elaborate

The quadrant was over 130 feet long and still survives today

The chief observer was Ulugh Beg, the governor and then Sultan of Timur (current day Uzbekistan, Tajikistan, Turkmenistan, Kyrgyzstan and Kazakhstan

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