Help

Support

Celeris is built by one person. Write to me — about bugs, about questions, about what you would like it to do. I read every mail and answer as fast as I can.

Reporting a bug

What helps most: the place and the moment being planned for. Almost everything in Celeris follows from those two values, and with them a problem can usually be reproduced directly.

• Place and moment — date, time, and roughly where the map had been dragged
• What you expected and what was there instead
• App version — under More → Info
• Device and iOS version — in Settings under General → About
• A screenshot, if the problem can be seen

Questions that come up

When is a night “dark”?

When the sun is more than 18° below the horizon — astronomical night. That is the window everything in astrophotography turns on. Celeris cuts it against moonrise and moonset as well: what is left is dark and moonless. If a night offers none of it, the app says so rather than leaving the line empty.

Does Celeris know whether the sky will be clear?

No. Celeris works out where the sun, the moon and the objects stand, and when it is dark. Clouds are weather, and weather is a different kind of question — for that you need a forecast. What Celeris gives you is the half of the problem that can be known in advance.

The moon's position is slightly off.

Moon positions are calculated geocentrically, that is from the centre of the earth. Close to the horizon that can differ by up to about a degree from the topocentric position you actually see. For planning a shot it makes no difference; for the exact moment of rise at the horizon it does.

Where exactly is the galactic centre?

Celeris approximates it by the position of 3 Sagittarii. The band of the Milky Way is not a point to begin with, and for the question “is the bright part high enough?” the approximation is more than close enough.

A place in the far north shows “no event”.

Rise and set searches are bounded in time. During polar day and polar night there simply is no rise or set within that bound — the app says so rather than searching forever.

Which time zone are the times in?

The one belonging to the place you are planning for. Not the one your phone happens to be in. Drag the map across a time zone boundary and every time is recalculated.

The widget shows a different place from the app.

By default the widget follows the place you last planned for. You can pin it: More → Widget location. There you can search for and pick a fixed place; a tap on “follows the app” releases the binding again.

Which focal length is the frame based on?

A full frame sensor (36 × 24 mm). The rectangle shows what a full frame body would take in at the chosen focal length — portrait or landscape. With smaller sensors the frame is correspondingly tighter.

Do I have to allow location access?

No. Your location is only asked for when you tap the arrow in the top row, and it is used for nothing but moving the map there. Decline and everything still works — drag the map by hand, or search for the place with the magnifier.

What can I search the catalogue for?

Proper names, HR numbers (Bright Star Catalogue), HIP numbers (Hipparcos), and for deep-sky objects the Messier number. It holds some 8,900 stars and all 110 Messier objects. Where the data comes from and how to download it is on the star catalogue page.

Can I see the introduction again?

Yes — More → “Show introduction again”, right at the bottom.

Which iOS version do I need?

iOS 26 or newer, on iPhone and iPad. The app is available in English and German and follows your device's language.