anker Powercore
My iphone is with me at all times, and I use a variety of sophisticated star apps; it’s not until you’re out in the field that you can match up the sky to the stars on the screen. There are apps to help find Polaris, too, and tell you when the International Space Station is passing. All these suck battery power – and smartphones don’t like the cold and die pretty quickly – so this gadget can recharge the phone twice over, if needed.