We have discovered that the eastern limit of the Baray (outer side of the eastern embankment) was located at 5 krta yuga - ie 2 Khmer arcminutes (2 kam) – from the centre of the East Mebon. This eastern limit of the Baray was used to determine the size of the Venus diagram which was also constructed from the same observer location as used for Mercury and the Sun.
By supposing the Sighra epicycle of Venus runs along the eastern outer embankment of the Baray, the planet itself (-31.86° from Sun) is located on the meridian of the Pre Rup temple (961 CE), the main monument of the capital founded by Rajendravarman.
More precisely, the meridian of Venus runs through the row of six towers constructed on the eastern part of the second enclosure.
Theoretically, the Venus meridian we have determined runs some 3 m to the east of the north-south median axis of the northernmost tower but we suggest the goal of the Khmer was to create a Venus meridian running along this median axis.
The latter crossed the reservoir dug some 300 m to the north of the temple. In the context of the planetary diagram, this reservoir has relevant proportions :
East-west length of reservoir = 55.5 m
North-south length = 34 m
(Measurements between median axes of embankments)
34 / 55.5 = 0.613
Period of revolution of Venus = 0.615 year.
It seems the revolution’s period, whose value was provided with great accuracy by Aryabhata, was coded in the reservoir crossed by the Venus meridian.
We have seen above that the Khmer used the centre of the epicycle of the Sun to determine the location of the East Mebon. We suggest they also used the Venus Manda epicycle to calculate the east-west width of the island’s retaining wall . The width of the latter (120 m) is practically equal to the radius of the epicycle (119.67 m).
Moreover, a Venus Sighra ratio is determined by the east-west width of the outer enclosure and the location of the temple’s central tower.
90.5 / 125.5 = 0.721
with 125.5 m = 4 kas = length of southern second enclosure (between inner walls)
(= 4 x diagonal of towers’ square of upper platform)
and 90.5 m = distance between south-east inner corner of outer enclosure and central tower.