A static single-page web app for planning a night of astronomical observation. Pick a target, a date and a location, and see where the object goes across the sky that night taking your horizon into account.
No backend, no accounts, no server-side state. Everything runs in the browser and everything you save stays in localStorage.
I like planning a session in Telescopius, but it doesn't know what obstructs my view. In NINA, I can create a custom horizon and it will overlay it on the target trajectory when planning, but NINA is running on a separate computer, which is usually attached to a telescope and requires VNC or RDP to connect to it.
SkyPath combines a (very much) simplified NINA search and a NINA horizon and displays it to you in your browser.
SkyPath draws two charts of the night, both centred on local midnight (the window runs roughly noon → noon):
- Altitude chart — the sky unwrapped: object altitude against time, with day, twilight and night shaded behind it, and your horizon drawn as the obstruction along the object's own azimuth track.
- All-sky chart — a circular down-top view. Rim is altitude 0°, centre is the zenith, north at the top. The obstruction is drawn as a wall around the edge and the target path as it moves across the sky.
A time slider under the charts links them: both flag the same moment with a marker. There is also a toggle to show the moon path and its phase.
Additionally, SkyPath calculates event times, in a 24-hour clock, local timezone:
- object rises above 0° / above your horizon
- object at maximum altitude (transit), with the altitude and direction
- object sets below your horizon / below 0°
- sunset, sunrise, and civil / nautical / astronomical twilight and dawn
- moonrise, moonset and the moon phase
SkyPath bundles about 15 000 deep-sky objects (Messier, NGC, IC, Sharpless 2 and LDN) plus the solar system planets, searchable by any designation or common name (M13, messier 13, NGC 6205, bare 6205, Sh2-155, Hercules). The catalogue model is multi-catalogue by design: an object belongs to many catalogues and carries many names, so M13 and NGC 6205 are one entry with two numbers, not two rows.
Observatories — named combination of a location and a horizon, created, edited, selected and deleted in-app, persisted to localStorage. The selected one drives every calculation and both charts.
Horizons are NINA-compatible plain text: one azimuth altitude pair per line, azimuth 0–359°. Upload a file or paste it.
npm test # all three Vitest projects
npm run check # svelte-check + tsc
npm run lint # ESLint (TypeScript + Svelte)
npm run format # Prettier
npm run catalog:build # regenerate catalogue JSON from OpenNGC and VizieRSvelte 5 + TypeScript on Vite, with astronomy-engine for all ephemeris math. Both charts are hand-rolled SVG — no charting library. Tests run on Vitest and Playwright.
This is the first project that I completely vibe coded. I've generated programs with AI before, but I always check the code afterwards to make sure I understand what it does and that it does it efficiently. This project is not it.
I am not a front-end developer. I can do some JS coding and just to have the app to look as I want to would have taken me a week.
I decided that I don't really care how it works (also Claude Code with Opus/Fable/Sonnet 5 combination generates fine code. I still find ways to improve it, but all-in-all it's not bad at all) as long as it works fast enough and looks the way I want.
Messier, NGC and IC are generated from OpenNGC, licensed CC-BY-SA-4.0 — attribution is a licence obligation and is shown in the app's credits. Sharpless 2 and LDN come from the VizieR tables VII/20 (Sharpless 1959) and VII/7A (Lynds 1962), cited in the same credits. The JSON under src/lib/catalog/data/ is generated by npm run catalog:build; don't hand-edit it.
- Times display in the browser's local timezone.
As this project is coded almost exclusively using LLMs, the only proper way to license it is to put it into public domain, thus this project is released under the terms of The Unlicense.