Celeris
DE·EN
Download
Celeris app icon

See the night
before you photograph it.

Celeris shows you where the sun, the moon, the galactic centre of the Milky Way or one of some 9,000 catalogue entries stands — for any place and any moment. One screen: a map, a time slider, the sky.

Download on theApp Store What Celeris does

For iPhone and iPad · German and English · No accounts, no trackers

Celeris showing the Milky Way in the full screen sky with a 24 mm frame and the stars Altair, Antares and Kaus Australis.
~8,900stars from BSC5 / HYG
110Messier objects
7twilight phases
0accounts, trackers, ads

The main features

Everything a night turns on — on one screen.

Sky over the map

Rise and set directions, the current position, the altitude and the band of the Milky Way — drawn around the spot you are standing on.

Endless time slider

A ribbon of twilight colours with no beginning and no end. The sun's curve, the moon's curve beside it — and the moon riding along on its own path.

Simulated camera view

Set the focal length and the direction and see what a full frame body would take in — portrait or landscape, with each object's day path behind it.

Finding dark nights

Astronomical night cut against moonrise and moonset. You can see which nights are dark enough — and which ones the moon spoils.

Object catalogue

Some 8,900 stars plus all 110 Messier objects. Searchable by name, catalogue number or common designation.

Place aware

GPS, place search — and the time zone of the place you are planning for. Not the one your phone happens to be sitting in.

Full screen sky

Stand underneath the sky.

One tap on the map puts the simulated view across the whole screen: every object at once, the sky turned directly with a finger.

Sun and moon are drawn here as bodies rather than as symbols — at exactly the size the chosen focal length gives them. A speck at 24 mm, a seventh of the frame at 400 mm. With the colour and the flattening the air leaves them at their altitude, and the lunar phase lit from where the sun actually stands.

  • Swipe to look around, pinch for the focal length
  • What a full frame sensor takes in, drawn as a rectangle
  • Star field from the full catalogue
Full screen sky with the band of the Milky Way, the star field and a 24 mm frame.
The moon at a long focal length, reddened by the air five degrees above the horizon.
Milky Way — the window known in advance
The sun in haze — direction and minute planned
Golden hour, to the minute

Map & time

Pick a place, pick a moment — the rest follows.

Drag the map to where you want to photograph. Everything is worked out for the point under the crosshair, in that place's own local time.

Then drag the time slider through the day: the map overlay, the twilight colours and every visualisation move with it.

  • The field of view cone of the chosen lens, on the map
  • Rise and set directions as lines from your position
  • “Now” jumps back to the current time
Main screen: the map with sunrise and sunset lines, the time slider and the main events of the night.
The map with the field of view cone and the chosen star's path, with visibility markers.

Visualisations

Swipe your way through the night.

Below the controls sit five views side by side: the main events, a day circle, the twilight phases for morning and evening, the full list of events and altitude curves for the sun, the moon, the Milky Way and the object you picked.

“Dark night” means the sun is more than 18° below the horizon — the window everything in astrophotography turns on.

Day circle with the twilight phases as a ring and the times for morning and evening twilight.
Twilight phases for morning and evening as two columns with start and end times.
Chronological list of events: the Milky Way sets, dark night ends, astronomical and nautical twilight begin, moonrise.
Altitude curves for the sun, the moon, the chosen object and the Milky Way across the whole day.

Focal length

What fits in the frame?

Set the focal length and the rectangle shows you what a full frame sensor takes in — in degrees, with the object's day path behind it. On the map the same frame becomes a cone around your position.

At 24 mm the cone spans half the valley. At a long focal length a narrow beam is all that is left.

Camera view at a long focal length with a 6° × 4° angle of view; on the map the field of view cone has become a narrow beam.
Camera view at 24 mm with a 74° × 53° angle of view, aimed at the galactic centre, with visibility times.

Planning ahead

The month at a glance.

Page ahead night by night: the lunar phase, and how long the Milky Way and the object you picked stand in a dark, moonless sky. Bar length equals usable time. Tap a night — and the app plans for it.

The catalogue is searchable by name and by HR and HIP number, and shows the right ascension, declination, magnitude and hours above the horizon for every object.

Month calendar with the lunar phase per night and bars for the Milky Way and Vega.
Star picker with Sirius, Canopus, Arcturus, Vega and others, each with coordinates and magnitude.

Widgets

The next dark night on your lock screen.

The Milky Way widget looks for the next dark, moonless night in which the band is up at all — for the place you last planned for — and draws the sky as a 14 mm frame for the moment the galactic centre stands highest. One tap opens the app on exactly that moment.

  • Home screen: small, medium, large
  • Lock screen: rectangular, circular, inline

On the astronomy

Honest about the maths.

Celeris calculates with SwiftAA following the standard methods of spherical astronomy. Where something is simplified, it is written down here:

The catalogue in use is derived from the HYG database by Astronexus and from OpenNGC by Mattia Verga, both under CC BY-SA 4.0 — sources, changes and download.

The night can be planned. The weather cannot.

Celeris tells you when it is dark and what will be standing over you. Whether clouds turn up is not something it knows — other apps do that.

Download on theApp Store