ClearSkys started with a telescope and a five-year-old.
I bought my son his first telescope, and quickly ran into the problem every stargazer in Northern Ireland knows: the weather. Cloud here is changeable and forecasts built for "will it rain" tell you almost nothing about whether the sky will actually be clear and dark enough to see anything. So I wrote a small script that emailed me each night when conditions looked good enough to set the telescope up.
Because the weather was so often not good, I had plenty of evenings indoors to keep working on it. That script grew into this site.
ClearSkys pulls weather data for any location worldwide, low, mid and high cloud cover, wind, humidity, dew point, and rain, and combines it with astronomical calculations for darkness, moon phase, planet visibility, satellite passes and aurora probability. It turns all of that into a single 0–100 score and a plain-language verdict, so you get one honest answer: is tonight worth setting up for?
It also works out your best viewing window, the longest run of high-scoring hours, so you know not just whether to go out, but when. You can read the full scoring methodology if you want to see exactly how each factor is weighted.
The forecast is only as good as its inputs, so they're worth being transparent about:
Where two weather sources disagree, ClearSkys exposes that as a forecast confidence indicator rather than hiding it. A forecast that's held steady across updates is more trustworthy than one that keeps changing.
Early feedback made one thing clear: not everyone wants the same sky. An astrophotographer cares about wind and moonlight far more than someone just stepping outside to look up; a planetary observer barely cares about light pollution but lives and dies by atmospheric steadiness. So ClearSkys has several observer profiles, General, Astrophotography, Visual, Planetary and Aurora, each of which reweights the factors, plus a fully customisable profile where you set your own criteria.
It's just me, Steven, an amateur astronomer and software developer in Northern Ireland. ClearSkys isn't a company or a funded startup; it's a personal project I keep improving because I use it myself, most clear nights. There are no ads and the core forecast is free.
My goal is simple: make the scoring as accurate and genuinely useful as possible. If you spot something wrong, have a location that isn't scoring well, or just want to tell me what you'd find useful, I'd like to hear it, hello@clearskys.app.