Stars

The Stars tool tells you when the Milky Way is visible in a dark, moonless night, which settings give pinpoint stars or beautiful trails, and when the galactic core will line up with your subject. It has four tabs: Night, Session, Direction and Season.

Place, date and equipment

• Place: by default, the phone’s GPS position. Tap it to search an address, enter coordinates or go back to your position with Here. Favourite places are shared by the Sun, Moon and Stars tools.
• Date: the arrows move to the previous or next night, Today goes back to the current night and tapping the date opens the calendar.
• Explore the night: a strip coloured by the light of the sky, with bands showing when the Moon is up and when the galactic core is high enough. Drag it to pick a time.
• Equipment: the camera and lens shown at the top of the screen are used for all the Session tab calculations.

Night tab

Tonight for the Milky Way: a verdict sums up the night (ideal night, short window, moonlit, out of season or no dark night), with:

• the length of the dark night (Sun more than 18° below the horizon) and the part without the Moon;
• the galactic core at its highest: time, elevation and direction;
• the celestial pole, around which the stars turn for circular trails;
• the Moon: phase, rise and set.

The Milky Way window is the longest part of the night that is dark, moonless, with the galactic core more than 5° above the horizon. Show moves the strip to that time, Plan opens the Planner and the bell sets a reminder. If there is no window tonight, the app shows the next one.

Starry sky in the coming nights? Once the option is on, a forecast gives the cloud cover, fog and rain during the Milky Way window, or else during the dark night. It is indicative and needs a connection.

Moments of the night: sunset, start of the dark night, moonrise and moonset, rise, culmination and set of the galactic core, end of the dark night, sunrise.

Session tab

Set the aperture, the focal length, the maximum ISO and the part of the sky you are framing (elevation and direction): the stars seem to move faster near the celestial equator than near the pole. Then choose the kind of photo:

• Pinpoint stars: choose how strict you are about sharpness. The app gives the longest speed without trails in each zone of the frame, then the recommended speed and ISO, the target exposure value and the resulting trail length, in pixels. The lens score compares how well lenses gather starlight: the higher, the better.
• Star trails: choose the trail length you want, in pixels. The app gives the exposure time needed at the centre and at the edge of the frame, and shows the star trails across the field.
• Night landscape: the sky exposure (stars without trails) and the longer foreground exposure with the same framing, plus the hyperfocal distance: the focus distance that keeps everything sharp from the foreground to infinity.

The app warns you when the exposure value stays above −5: the photo may be noisy. When the exposure is longer than one second, a floating countdown button times it.

Direction tab

When will the galactic core be in line? Choose the direction of a subject (tree, lighthouse, rock arch): the app finds the nights in the next 12 months when the galactic core stands in that direction, in a dark night, without the Moon and above 5°.

• Set the direction by hand or aim with the phone; Lock the aim freezes the direction. The tolerance widens or narrows the accepted gap.
• Terrain relief (real horizon) takes mountains and hills into account.
• The sky seen from above view shows the Milky Way at the chosen time (band) and the path of the galactic core during the dark night (line); the compass helps you get your bearings on site.
• Tap a night to show it; the bell sets a reminder, Plan opens the Planner and Augmented reality shows the Milky Way in the scene.

Season tab

A view of the whole year to choose your outings:

• Milky Way season at your latitude, number of useful nights (window of 30 minutes or more) and galactic core at best (its greatest elevation).
• Milky Way window, night by night: a chart of the window length each night, with the part lost to the Moon.
• Best nights: one per lunar cycle, with an optional reminder.
• Alert me on Milky Way evenings: a notification at 6 pm on each evening whose window lasts at least 30 minutes, for the next 30 nights (renewed each time you open the tool). Weather is not included: check the sky in the Night tab.
• Month by month: the number of useful nights and the longest window of each month.

The further south you are, the higher the galactic core climbs: it gains about one degree of elevation per degree of latitude.

Shooting tips

• Weather and place: you need a clear sky and a spot far from city lights. Get as far as possible from light pollution.
• Equipment: a sturdy tripod, a remote release (remote control, intervalometer or self-timer) and a fast wide-angle lens.
• Focusing: manually, on a bright star in magnified view. On a tripod, turn off stabilisation and long exposure noise reduction.
• Star trails: take a continuous series of short exposures with an intervalometer, then stack them. It produces less noise and heat than a single very long exposure. Keep a spare battery warm.
• Foreground: shoot it during the blue hour or with a longer exposure, without moving the tripod, then blend it with the sky shot. Use a headlamp in red light to preserve your night vision.