Method and apparatus are provided for a hand-held planetarium which
displays a sky pattern comprising graphical representations of one or
more celestial objects. A sensing system comprising one or more sensors
provides information about an orientation of the device. A controller
receives the information about the orientation of the device from the
sensing system and determines therefrom an altitude angle of a pointing
axis and an azimuthal angle of the pointing axis. The controller accesses
a database of celestial objects and determines, 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.
Graphical representations of the one or more selected celestial objects
are displayed on a display screen. The planetarium may switch between a
normal orientation mode and a downward facing orientation mode.