Time & Place

Before you can use Planisphere for stargazing, you need to let the program know where you are.

Select Options --> Time & Place from the menu. Tap the world map to indicate your approximate location, then adjust it further by tapping the triangular arrows. Absolute precision is not necessary for casual stargazing.

Make sure your time zone (offset from Greenwich Mean Time) is accurate. Remember to adjust your offset from GMT if Daylight Saving Time is in effect.


Why Is My Location Important?

The sky looks different from different places on Earth. For example, the star Polaris never sets in the northern hemisphere, but in the southern hemisphere it never even rises above the horizon. Your latitude determines which stars you can expect to see from where you are.

Your time zone is also important. The movements of the stars and planets are calculated for Greenwich, England, and have to be adjusted for the time difference. But even within the same time zone, longitude makes a difference as well. The eastern edge of a time zone is a whole hour ahead of the western edge, even though the clocks in both places tell the same time. When the sun rises at 6am at the eastern end, the western end will have to wait until 7am for the same sunrise.


How Do I Adjust For Daylight Saving Time?

Add one hour to your offset from GMT. For example: -5+1=-4. In other words, normally you are five hours behind GMT; but in the summer you move one hour closer to it because you 'spring forward' and GMT doesn't.