Hi richard,
I guess the American is right.. if you connect the controller it will introduce noise to the Nexstar unless you have some passive filter on your controller. If the controller just connects to the battery it should not be much of a problem since the battery should not be introducing noise to the controller since it is not a step down from AC to DC and no transistors are used. Also, the heat sink is important as the IC would definitely dissipate heat since it supplies the current to the heaters. Still wondering.. are you not going to make heaters for your EPs? Cos at Mersing, the EP also will dew up if you don't do something about it and leave it in the open environment.