Bankers for the deal are understood to be Craigs Investment Partners and Deutsche Bank.
Market sources said yesterday that the sale had been tendered by News Corp and the investment banks were effectively underwriting the deal.
No cornerstone shareholder is expected to take a stake in excess of 19.9 per cent - a level that would require a full takeover offer to be made.
A spokesperson for Sky TV said yesterday that the company could not comment on matters relating to shareholdings.
Another substantial shareholder - the Todd family - sold its 11.11 per cent stake in Sky TV in November last year to Credit Suisse, which on-sold it to institutions and private investors.
That block of shares was sold at $5.05 a share for about $218 million.
The on market selldown of Sky TV also follows media group Fairfax's $769 million selldown of Trade Me in December.
This latest selldown will further add to the depth of the local market and gives the NZX another boost as it prepares for the partial float of Mighty River Power.
Murdoch's News Corp is a global media giant which owns 20th Century Fox, the Fox News cable channel as well as newspapers like the Wall Street Journal. It is the parent company for Australian publishing group News Ltd - which owns the Australian and Sydney's Telegraph - and British-based News International, publisher of the Sun and the Times.
It has been the dominant shareholder in Sky TV since late 1999 when it took control through newspaper company INL.
Last month Sky TV reported a 9 per cent gain in first-half profit as subscribers migrated to its MySky premium service and spent more.
Profit rose to $68.2 million in the six months ended December 31, from $62.7 million a year earlier.
Sales rose 3.9 per cent to $443 million.
Total subscribers to Sky TV's services were little changed at 846,988 at December 31 from a year earlier, though the number on MySky climbed 28 per cent to 423,973. Average revenue per subscriber rose to $75.78 at December 31 from $71.81 a year earlier.
Murdoch's investment in a German pay TV channel late last year fuelled speculation he might sell out of Sky here.
Sky was formed in 1990 by a group led by Craig Heatley with three UHF channels in the upper North Island and struggled in its early years.
