Starmap displays the celestial sphere for any future, present or past dates. Touch the Time and Date icon in the main menu to access the time settings panel.
When the map is in real time, the ephemeris will be refreshed every minute and the map will be automatically recomputed. Setting the map in real time mode happens by touching the Now button in the top menu bar. Setting a future or past time will freeze the map for these times till you press the Now button again.
When the map is not in real time mode, the date is displayed in grey in the top right corner of the map to let you know that the map does not show what you will see in real.
Touching the date lets appear the classical dials of the iPhone and can be used as those of your main device settings. (Note that changing the time in Starmap, does not affect your device settings). There are also two time presets:
- Midnight sets the time to 12pm exactly for the present date.
- Sunset sets the time when the Sun just reaches the horizon.
The purpose of these presets is to give you a quick way of setting the map to the next night configuration, if you are planning it during the day.
The local sidereal time is indicated for your present longitude (as set in the Location settings). Touching it gives access to the polar alignment view, as used in many polar scopes of equatorial mounts. You will find this feature very practical on the field when trees or buildings hide the reference constellations…
The Julian day used for the ephemeris computation is also displayed.
The map time can also be modified live on the map with the time slider mode. Press the time slider icon in the main menu and slide your finger on the screen to change the time and look at the map evolving. The touches on the screen now act differently.
- sliding your finger horizontally changes the time.
- sliding a finger vertically changes the day
- sliding two fingers vertically changes the month.
- a double tap sets the map back to the time used as you turn the time slider on
Once finished, decide to keep or cancel the time changes with one of the two buttons on the bottom of the screen. This mode is particularly interesting for finding conjunctions for viewing evolutions of comets or asteroids along the days.
One precision regarding the planets positions when using the time slider:
Starmap uses a quite CPU demanding computation based on elliptical series in order to compute the position of the Solar system bodies. This is perfect when computing the ephemeris all minutes. However, the ephemeris in time slider mode are restrained to simple elliptical solutions, in order to cope with fast screen refresh rates. When leaving the time slider mode, you can notice that some objects will slightly move, once the complex ephemeris calculation has been applied at new.