I strongly recommend the Star Walk app. It might cost you a couple of quid, a one-off, but it's incredibly beautiful. Point your phone or iPad at the sky and it tells you exactly what you're looking at in glorious view. Move your device around and you can follow the sky around, even below the horizon, and there are lots more facets to the app. I wouldn't be without it. Apart from Daily Art, it's my very favourite app.