Time Controls
The Time Control panel at the top of the screen is used for stepping forward/backward in time.
Tap the [+] and [-] buttons to change the current step period- Tap the Time Step button to jump the current time forward or backwards by the selected period
- The Fwd/Rev sets whether the time steps should be forwards or backwards in time.
- Reset Time sets the current time back to now.
- Tap the Run/Stop button to animate all views in increments (as specified by the step period)
The available time step periods are: 1 Minute, 5 Minutes, 1 Hour, 4 Hours, Sidereal Day, 24 Hours, Lunar Day, 1 Week, Lunar Month, Calendar Month, Calendar Year, Tropical Year. Of these, several deserve further explanation:
Sidereal Day: slightly less than 24 hours, this is the time required for the Earth to rotate such that a fixed point in space (eg a background star) is visible in the same part of the sky from one period to the next. It is essentially one complete Earth rotation without the extra rotation caused by the Earth’s orbit around the Sun.
Lunar Day: slightly more than 24 hours, this is the time required for the Earth to rotate by roughly 1 day but keeping the Moon in the same part of the sky from one ‘day’ to the next.
Lunar Month: this is time that it takes for the Moon to make one complete revolution around the Earth, adjusted for the Earth’s orbit around the Sun so that the Moon’s phase is the same from one Lunar Month to the next.
Tropical Year: roughly 365.25 days, this is exact time that it takes to make one complete revolution on its orbit around the Sun. The 0.25 accounts for our leap years so that our Calendar year is kept roughly in time with the Tropical Year by adding an extra day every 4 years (or so).
View Selection
Swipe the main view left/right to switch between the 4 displays: Orrery, Sky View, Sizes View, Data View.
Planet Selection
The panel at the bottom of the screen is used to select which Object should be highlighted in the main view.
