ASTRONOMICAL

INSTRUMENTS

SUNDIALS

(16th Century B.C. or earlier, Egypt) The ancient Egyptians were one of the

first cultures to widely divide days into generally agreed-upon equal parts,

using early timekeeping devices such as Sundials, Shadow Clocks, Merkhets

& Plumb Lines used by astronomers of the period. In times when people's

activities were limited to daylight, shadow-casting instruments called

gnomons were used to distinguish broad divisions in the daytime. Gnomons

were eventually combined with scales to produce sundials, which allowed

people to tell time by measuring the length or direction of the shadow cast

by the Sun. An Egyptian Sundial from about 1500 B.C. provides the earliest

evidence of the division of the day into equal parts. Marks on the dial link

the length of the gnomon's shadow to a standardised unit. The ancient

Egyptians made the first Sundials. Before the division of the day-night period

into 24 equal hours, the number of hours counted during any period of

daylight was held constant across the seasons; thus, an hour in summer

lasted longer than an hour in winter because the daylight period itself was

longer. Sundials had to be specially made for different latitudes because the

Sun's altitude in the sky decreases at higher latitudes, producing longer

shadows than at lower latitudes. Not everyone in the ancient world realised

this. Interestingly, a Sundial brought to Rome (4154' N) from Catania,

Sicily (3730' N), in 263 B.C. told Romans the incorrect time for almost a

century.

ASTROLABE

Muslim astronomers care about manufacturing this astronomical device, The

Astrolabe, which they inherited from the Greek civilization, they also

developed it, and wrote great valuable books on how to use it. The usage of

this remarkable device, astrolabe, continued until the nineteenth century

and it is not known specifically who invented it, some referred to the Greek

Scientist Hipparchus (BC) as mentioned in Ptolemy's book, Almagest (150

CE) Muslim scientist Mohammed ibn Ibrahim al-Fazari (died in 180 AH) is

the first scientist to write a book in description, manufacture, and the use of

the astrolabe, and he was the first who have made Astrolabe in Islam.

Muslim scholars and scientists concerned about the Astrolabe and gave

much attention to its huge role in determining the times of worship

(Prayers), the direction of Mecca, and the solar and lunar eclipses, as well as

its important role in astronomy and making Zij (Astronomical Almanac),

determining distances, and to identify scientific measurements and most

importantly the knowledge of the time at night by the stars and during the

day by the sun , so The members of our astronomical society made a lot of

astrolabes to understand it and to know how to use it.

SHADOW CLOCKS

Shadow Clocks, another form of Sundials came into usage. The Shadow

Clock divided night time into 50 parts, with an additional 2 twilight hours in

the morning and evening. It was made up of a long stem divided into 6

parts, and an elevated crossbar that cast a shadow over the marks. This

early clock was positioned eastward in the morning, while at noon it was

rotated to face west, measuring as the sunset in the opposite direction.

Ancient Egyptian Obelisks were larger, more public designs of Shadow

Clocks; markers around the obelisk would indicate units of time, and

indicated morning, afternoon, the summer solstice (the longest day of the

year), and the winter solstice (the shortest day of the year).

QUADRANTS

Quadrants mean a quarter of circle made on the wall or paper for use in

observations and invented by the Muslims and the Quadrants were

important instruments at the great observatories as in Maragha and

Samarqand Observatory, where Ulgh Beg built in Samarkand observatory

huge Quadrants( around three floors tall) and others Reference has been

made for when Ptolemy Quadrant on the wall The small Quadrants made

from metal or wood was invented by Muslims in the third hijri century and

has several types of them as : Quadrant of almucanteres is a quarter of the

astrolabe where the altitude lines are drawn called almucanteres. Sine

Quadrant is a quarter depends on the Sine and cosine of the angles used in

trigonometry, Professor Samir El-aidy member of Astronomical Society made

a lot of quadrants.

WATER CLOCKS

An early Egyptian Water Clock, dating to about 1500 B.C., was found among

other items in the tomb of the pharaoh Amenhotep I of the 18th Dynasty,

their creation is attributed to an inventor named Amenemhat. Early water

clocks were bowl-shaped, with a small hole in the bottom. It is a little stand

with a pot on the top of the stand and a pot at the bottom of the stand. The

pot at the top of the stand had a hole drilled in the side. This pot was then

filled with water and the water would flow out of the top pot down to the

bottom pot. When the water was at a certain level, it was a certain time.

Markings on the side, at even intervals, indicated the passage of every

twelve hours. Water clocks were useful as people could accurately measure

time, in all seasons, and even during the night. Another type of Water Clock

had a float in the water. The float is connected with a 'hand' indicating the

time on a board.