I'm an experienced sky watcher in the west of ireland and know very well what aircraft look like, i live on a busy air corridor from the us to europe. i also know what a satellite and space debris looks like. tonight i seen a strobe like flash in the sky to the north west from the corner of my eye and again several seconds later. i fixed the spot and counted 13 seconds between flashes. a single white strobe like flash. i initially appeared not to be moving but i soon realised it was moving considerably slower than an aircraft or way slower than a satellite and space debris. it took over an hour to cross the sky and seemed to be at great altitude or in orbit. i checked flight radar 24 and several satellite tracking apps which had nothing. i didn't expect to see anything on those apps as it was moving relatively slowly.I tried to capture a video but my phone wasn't up to the job. i watch the sky on a nightly basis and seen loads of strange stuff which i could explain but this was ver different, but at all dramatic, from any thing i've seen.