While Vijayadashami is used to recall many heroic events of the glorious history of Hindu civilization, historically speaking there is no connection between Ashwin Shukla 10 (Vijayadashami) and Ramayana.
(1/n)
Rama arrived at the Ashrama of Sage Bharadwaj, from Lanka on Vaishakha Shukla Panchami (12 January 12208 BCE)
Rama met Bharata on Vaishakha Shukla 6 (nakshatra Pushya) , i.e. on 13 January 12208 BCE.
(2/n)
It is a long story. Here are a few initial steps.
1. Theory: All astronomy observations of Valmiki Ramayana are factual observations of Ramayana times
(3/n)
They amounted to 575+
They include positions of the cardinal points with respect to nakshatra, North pole star of Ramayana times, planetary positions and conjunctions, descriptions of lunar months and correspondings seasons, eclipses.
(4/n)
Sometimes individual pieces at a time and other times a group of evidence together!
(Sequence, association, gradation) is important.
(7/n)