The stock fell to $28.7 (£20.2) from $30.4 (£21.4) last night on Nasdaq, as Wall Street analysts said that they largely applauded the move which, if successful, would scupper Rupert Murdoch's ambition to move into the US pay-TV market.
However, there are doubts that a combination between the two US satellite broadcasters would, in the long term, prove successful.
Ray Schleinkofer, an analyst at Thomas Weisel Partners, said, "EchoStar's bid is not the probable outcome. I still think there's anti-trust concerns. We haven't heard Hughes' response and we don't know if Murdoch will come back with a sweetened offer."
EchoStar, which operates under the Dish Network name, said on Sunday that its offer would provide synergies of $56m (£39.6m) from the combination. Hughes shares are expected to rise on the 18% premium EchoStar has tabled.
Even if its bid is not successful, EchoStar could stand to gain from the situation. Schleinkofer said, "EchoStar will be competitive even if its offer is rebuffed. [EchoStar chairman Charlie] Ergin's bid drags this process out and the longer it drags out, the more Hughes runs the risk of becoming unfocused. As a result, EchoStar could benefit by taking market share away from Hughes."