Even with nifty closed, with what reference does sgx nifty trade. And more importantly how does our nifty open very close to that value, since nifty is dependent on 50 stocks
SGX nifty trades on the singapore stock exchange, check this link for the market opening and closing time. So the Singapore exchanges are open almost 2.5 hours before Indian markets open.
Since only the Nifty trades on SGX and not the underlying stocks, the value is basically just a consensus of all the global players based on international factors and values at which other indices are trading at. As and when we get closer to market opening in India, consensus builds and more people start participating and hence tend to open very close to where Nifty in India is likely to open.
This kind of shows how the very influential players(institutions) on Indian markets, probably have access to SGX Nifty as well.