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Rub ul Mujayyab


In Arabic "Rub" means a quarter and "Mujayyab" means marked with "sines". Rubul mujayyab is an instrument for measuring celestial angles. It was used by the medival Arab Astronomers and navigators till the arrival of modern instruments.
     Jamaluddeen Abduullah Maradeeni , an Egyptian scholar of 16 th century wrote a book named "Risalah fi amali rubul mujayyab" and explaind 20 uses of the instrument in it including finding of the horizontal altitude of a celestial object and ,finding of latitude a place
        The instrument is quarter of a circular disc made of brass or wood graduated it's arc part with 90 degrees . It is called "Qaus"in the Arabic.The lines from both ends of the Qaus to the centre of the circle and it's 60 perpendicular lines are called "Jaibs". There are 2 flaps or cuttings in one side of the Jaibs and are called "The Hadafs"to use as vewpointers.A chord from the pinhole of the centre is called "Khaith"to use as plumb line and degree pointer. 
 To find the horizontal altitude of a celestial object.
Hold the instrument  as the vew pointer  and the object in a plane. If the object is the Sun move or turn it till the shadow of upper flap covers the lower flap and read the plumb line that is the altitude of the
 sun from the horizon that time.If the object is some stars or planets , the vew it directly with eye through the  hadaf.  





Malabar region of Kerala  State, India is famous for it's Islamic cultural heritage. In the first century of hegira itself 28 Masjids were built here and all were the centers of culture and education . There prevailed a system of education called DARS and along with other religious topics . In these “Dars System” Mathematics ,Asronomy, Logic, Medicine and other subjects were taught by the scholars.

Muslims need to observe the moon for calculation of lunar months and they observed the apparent movement of the Sun to tell prayer times. In 18 th century AD Umar qadi of Veliyankode near Ponnani wrote a song to find the prayer time of ASSR and it was composed of Arabic and Malayalam verses. It can be translated as follows:

 In Aries and Leo eight feet,

And nine in Taurus, Gemini and Cancer.

Nine and a half in Pisces and Virgo,

And Ten and a half in Aquarius and Libra.

Eleven and a quarter in scorpio and Capricornus

And eleven  and three quarters in Sagitarius.

This calculation is correct only for

A place between Ezhimala and Chettuva said Qadi bin Ali.


 Umer Qadi was a well known poet wrote

 in the Arabic.        

This song is on the basis of approximate assumption that a  person's height is 8 feet to his own foot.It's last 2 lines are purely in the Arabic. Even before 30 years this song was used to measure the shadow to tell Assr prayer time and I saw my grand mother doing so when I was a student. I have collected these verses from her who was expired on March, 2006.


قصيدة الظل والأقدام

شهرين الحمل والأسد فيهما ثمانية أقدام

وتسعة في الثور والجوزاء والسرطان

تسعة ونصف في الحوت والسنبلة

وعشرة ونصف أقدام في الدلو والميزان

وفي العقرب والجدي أحد عشر وربع

واثني عشر إلا ربع في شهر القوس

هذا الحساب قد استوي من أيلي

حتى لشطوي قال قاضي بن علي