The ship, which had arrived in on Saturday morning, was laden with scrapped cars bound for dismantling and recycling in mainland Europe.
It was ready to sail on Sunday evening and under the guidance of pilot Redmond Gillen, was manoeuvred silently up the Sligo channel, with only the foghorn breaking the calm night when the ship was opposite the village of RossesPoint.
The reason such an event was possible was because of work carried out to install lights all along the channel, capable of guiding ships along the treacherous narrow path into and out of Sligo Harbour.
The lights stretch from close to the westernmost end of Sligo docks right out to beyond Rosses Point Yacht Club and the January Perch.
The lights are run on solar power, absorbing enough electrical energy during the day to power them at night. The new development was completed a number of months ago, but got its first practical use on Sunday night last shortly before midnight.
It is hoped the development will allow a quicker turnaround time for ships coming into Sligo Harbour, particularly as the winter brings shorter daylight hours.