Dating of ramayana
An attempt to fix the dates of the events in the Mahabharat era, mainly based on internal astronomical records. However, archaeological and literary methods can only provide approximate datelines and for determining the precise time of the Ramayanic events, astronomical calculations may alone be useful.
Astronomical Dating Mahabharat states that Sage Vishwamitra started counting nakshatras from Shravana (Aadiparva A.71 and Ashwamedha A.44) and a new reference to time measurement thus initiated.
Dasharatha's nakshatra appears to be Krittika. Valmiki has beautifully described the sky (Ayodhya 41/10), when Rama left for forest exile.
He states, "Crux (Trishankhu), Mars, Jupiter and Mercury have cornered the Moon. Crux is on line with Hasta (Corvus) on the southern side. Calculations show that Jupiter was in Poorvashadha at 251 deg.
The Summer Solstice fell on Ashwin Full Moon, so the Sun was diagonally opposite at Swati nakshatra.
This astral configuration can be calculated to have occured around 7400 B. Kishkindha 26-13 describes the commencement of the rainy season.
Some historians of the past even refuse to acknowledge that Rama and other characters from the Ramayana even existed.On the eastern side of Hasta, there are Chitra, Swati and Vishakha. Pushya was at the western horizon with the setting Moon.On the southern side, from the west to the east, all the other planets were situated.He was coronated in the same month and one month later, proceeded to Ashokavan with Seeta (Uttar 41/18) when the Shishira Rutu terminated.So it seems that Vaishakha Masa coincided with Shishira.