Patent ID: 8684745

Claim:
A hand-held device for displaying a sky pattern comprising graphical representations of one or more celestial objects, the device comprising: a sensing system comprising one or more sensors for providing information about an orientation of the device; a controller configured to: receive the orientation information from the sensing system and to determine therefrom an altitude angle of a pointing axis and an azimuthal angle of the pointing axis; access a database of celestial objects and determine, from within the database, one or more selected celestial objects for display based at least in part on a measure of proximity of the celestial objects to the pointing axis; and a display screen for displaying graphical representations of the one or more selected celestial objects; the controller configurable to operate in: a normal orientation mode; and a downward facing orientation mode, where the controller is configured to receive the orientation information from the sensing system and to determine therefrom a modified altitude angle of a modified pointing axis and a modified azimuthal angle of the modified pointing axis and to use the modified pointing axis in place of the pointing axis for determining the one or more selected celestial objects for display; wherein the controller is configured to determine the modified altitude and azimuthal angles of the modified pointing axis by performing a coordinate system rotation transformation on the pointing axis, the coordinate system rotation transformation based on the orientation information from the sensing system.