Attention: Unfortunately, the app keeps getting bad reviews because the compass or spirit level doesn't work. This is then because the device does not have a compass sensor or a tilt sensor. An understanding from the buyer is very rare. A refund is of course possible. So please convince yourself before buying whether your device has the following sensors. manual: https://www.kechkoindustries.de/polaraligner-pro -Compass sensor -Tilt sensor -GPS The Polar-Aligner is a simple astronomical application for the northern hemisphere to help you to align your mount easily. It includes basic tools for leveling your equatorial mount (spirit level) and to adjust it to north (compass). Now you can calibrate your spirit level with a real spiritlevel and have the highest accuracy for a smartphone. New!!! Now the daylight alignment is included (beta version) The GPS gives you the most accurate information about your location with the altitude and calculate the position of Polaris and show you graphically the Polaris position or you switch to the northern Sky map and it shows you the Ursa major, Ursa minor and cassiopeia too. (Northern Polar Alignment). You get also information about Drift-Alignment. The tool helps you to get the right direction for the alignment. With the calculator, you can get the calculated result to align your mount with a small error. There are many Polarscopes for: IOptron Meade Orion Sky Adventurer Skywatcher Astrophysics Takahashi Bresser Vixen Celestron If you miss a scope, write us!