SHABNUMA-ROZNUMA BY NASIR AL-DIN HASAN (1218/ 1803)
In the early part of the fifteenth century, Padmanabha invented an
instrument called Dhruvabhrama-yantra. It consists of an oblong metal plate. On
one side is a horary quadrant with which time can be measured in the
day time. On the reverse is a nocturnal which measures the sidereal
time at night on the basis of the apparent rotation of the stars
around the pole star.
present instrument can be called an Islamic version of the
Dhruvabhrama-yantra, and is therefore important for studying the
history of the exchange of scientific knowledge between the
Sanskritic and Islamic traditions in India. We do not yet know if
Nasir al-Din Hasan was the first one to make such instrument or
there were others before him.
inscription states that it was made on the orders of Munshi Sahib
Walashan Lalah Pyare Lal in 1218 AH (1803 AD) at Bareilly. It is
calibrated for the latitude of 280 N, which is
approximately the latitude of Bareilly (modern values are 28; 220
N and 79; 270 E).
It is an
oblong copper plate measuring 178 x 174 mm. On the Shabnuma
side, there are seven circular scales engraved around the centre.
Two indices are pivoted to the centre. With these one can measure
for any moment of the night, the time in ghatis, and
determine the ascendant and the culmination.
reverse side, designated as Roznuma, is actually a sine quadrant (rubí
al-mujayyab). There is 176 mm long graduated index with which
time in ghatis or the solar altitude in degrees can be
measured in the daytime.