Showing realistic horizons on mobile computing devices

In general, this disclosure describes techniques for providing a user of a computing device with the ability to view a realistic map of the sky based on information associated with the current location of the user. The information may be geographical information, orientation or directionality of the computing device, time and date, and zoom settings of the computing device. The computing device may use built-in capabilities (e.g., compass) and applications (e.g., maps and GPS) to determine the current location information. The computing device then uses the current location information to obtain celestial and topographical information. Using the celestial information, the computing device displays a map of the sky with the appropriate celestial bodies. Additionally, the computing device uses the topographical information to display a realistic rendering of the horizon, such that objects in the horizon may be displayed to render a realistic representation of the sky from the current location.