Krepusko: finding the new moon on the horizon

The problem

Every Islamic month begins when the new crescent is seen, and almost nobody knows where to look. It is a hair of light just above where the sun went down, for about fifteen minutes, in a part of the sky that is still bright — so people look up, see nothing, and learn nothing.

The plan I wrote

For the exact place you are standing, the app works out where on the horizon to aim, what minute to start, how long the window lasts, and whether the crescent is too thin for eyes alone. It works with no internet.

Then it gathers what people actually found — those who saw it and those who looked and did not — and shows the evening as a whole. When a claimed sighting could not have happened, it says so from the physics and suggests what the person most likely saw instead, such as Venus. It never declares when the month begins: the scholar decides.

The build

AI coding agents built it from my written specification. My work was the specification, the tests it had to pass, and the review.

The proof

The astronomy follows published crescent-visibility criteria (Yallop and Odeh), and the app refuses sightings that are physically impossible. 23 of 23 automated tests passed.

On a real Infinix phone, the signed release build passed a cold start, all six main screens, a real change of place to London, and a restart that kept everything — with no crashes.

The launch

Live on Google Play, with screenshots for phones and tablets.