What's the best way from Skopje, Macedonia to the Cyclade Islands, Greece?

We're planning a Balkan tour from Jul 25th to Aug 7th, starting from Split, Croatia and all the way down until the Greek Islands, and so far we have everything set up until Skopje; however I can't find reliable info on Internet about timetables for the ferries going there (looks like the timetables are variable depending on the month). Does any local have any useful info? We'd so love to visit Santorini, I've heard great reviews about that place. Thank you!