Sky
In the workshopThree things to find, nightly
Store name: “Sky: Stargazing Tonight”
See it run.
About twenty-five seconds of Sky doing its job, recorded straight off the phone. No captions, no voice-over, nothing staged — the same clip the App Store shows.
Watch on YouTubeComing soon
Not out yet — but it’s close.
Every night Sky looks at the sky from where you are standing and picks three things worth going outside for: the Moon at its phase, the best-placed bright planet, and a shape or a star in season. Only things that are actually up, and only between dusk and the small hours — if it is not dark yet, it says when it will be. Then you hold the phone up, point, and catch them.
- Positions computed on the device from Meeus, Astronomical Algorithms (2nd ed.): the Sun from ch. 25, the whole of ch. 47 for the Moon — both tables, sixty terms each — and the planets from ch. 32/33 over a truncated VSOP87D, with light-time, the FK5 frame, nutation and aberration
- Checked against JPL Horizons: the planets land inside 2.5 arcseconds, the Moon inside 10, the Sun inside 13 — the engine's error budget, not the app's
- Stars from the IAU Catalog of Star Names with magnitudes and spectral types from the Yale Bright Star Catalogue, precessed from J2000 to tonight; showers from the International Meteor Organization's working list, dated by the Sun's longitude rather than a calendar day that drifts
- A planisphere drawn stereographically — the zenith at the centre, the horizon at the rim — that you turn with a thumb to run the night forward, hour by hour
Free web tool
What can I see in the sky tonight?
Start with when, because the sky is not dark when the Sun goes down. The useful window opens at civil dusk, about half an hour after sunset, when the Sun is six degrees below the horizon and the brightest planets show; it is properly dark at astronomical dusk, when the Sun reaches eighteen degrees down and the last of it leaves the upper air; and it closes at first light the next morning. Then work out what is genuinely up inside that window, from where you are standing — the sky over Seattle is not the sky over Nairobi, and a star that rises at four in the morning is not tonight's problem. Anything under about ten degrees of altitude is in the trees and the rooftops, so it does not count, and anything that clears that floor for less than twenty minutes is gone before you have your shoes on. What is left, on an ordinary night, is three things worth going out for. The Moon first, because it is unmissable and its phase changes what everything else looks like. Then the best-placed bright planet — not simply the brightest, because a brilliant Venus ten minutes off the horizon is a worse errand than a steady Saturn that is up all evening. Then one shape or bright star in season: the Summer Triangle, the Big Dipper, Orion, whichever is actually high. A meteor shower on its peak night is added as a fourth, and so is a conjunction — two planets, or a planet and the Moon, close enough to hold in one glance, which is the most striking thing an ordinary sky ever does. The panel below does that arithmetic for your own doorstep and draws the answer on a planisphere you can turn through the night.
Your location stays in the browser: the sky is computed here, and nothing is sent anywhere.
The sky is different from every doorstep. Say where you are standing and this works out what is worth walking outside for tonight.
70 cities built in, or the browser can ask your device.
Where every number here comes from
Positions are computed in your browser from Meeus, Astronomical Algorithms (2nd ed.): the Sun from chapter 25, the Moon from chapter 47 in full — both tables, sixty terms each — its phase from chapter 48, and the planets from chapters 32 and 33 over a truncated VSOP87D. Star positions are precessed from J2000 to tonight (chapter 21), because the equinox slides about fifty arcseconds a year and an unprecessed star is already a third of a degree out of place. It is the same engine the app runs, and it is checked against it at 34,000 points before this page ships.
Stars. Proper names, HR/HIP identifiers, V magnitudes and J2000 positions are the IAU Working Group on Star Names Catalog of Star Names (IAU-CSN, 2022-04-04). Spectral types are the Yale Bright Star Catalogue, 5th Revised Ed. (Hoffleit & Warren 1991), VizieR V/50. Three Bayer-only stars that an asterism needs (gamma Cassiopeiae, phi and tau Sagittarii) have no IAU proper name and are taken wholly from V/50. V magnitudes and spectral types are V/50's. Every row was cross-checked between the two catalogues: positions agree to better than 0.05 deg and the two independent V magnitudes to better than 0.2 mag, on every row. brightnessRank is computed over whole systems - BSC rows closer than one arcminute are summed into one light - so it matches the conventional list of brightest stars rather than counting the components of a double twice. IAU Catalog of Star Names (IAU-CSN), IAU Division C WGSN, last updated 2022-04-04; Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991), VizieR V/50.
Asterisms. Eight star patterns. The member stars and their J2000 positions come from the star catalogue and are checkable. The line segments are the conventional way the pattern is drawn, not a measured quantity. NASA, What Are Asterisms?; NASA Night Sky Notes, Connecting the Dots with Asterisms.
Meteor showers. International Meteor Organization, 2026 Meteor Shower Calendar, ed. Jurgen Rendtel, IMO INFO(3-25), Table 5 'Working List of Visual Meteor Showers', page 25. The row is transcribed verbatim in sourceQuote. peakSolarLongitude is the datum that does not move from year to year; peakMonth/peakDay are the IMO's 2026 dates, which the table itself says are 'accurate only for 2026', so the app dates each peak by solving for the Sun's longitude instead. The radiant is the position at maximum; it drifts about a degree a day across the active period and Sky only ever shows a shower on its peak night. IMO 2026 Meteor Shower Calendar, Table 5, page 25; The same PDF, Internet Archive capture of 2026-09-05 02:53:31 UTC (imo.net is offline).
Facts. One sentence per collectable object, each traced to a NASA page and the exact sentence it rests on. NASA Science — one page per object, the sentence quoted in the app's own data file.
Take it with you
The full Sky app turns the answer into something you go outside and do: hold the phone up and swing toward tonight's target, and the reticle warms as you close on it — ticks quicken, a tone rises, the ring tightens — until you are on it for a second and it catches, in a flash of sparks, and an enamel pin drops onto your board. The album collects every one of them: eight Moon phases, five planets, the brightest stars, eight shapes, ten meteor showers, with a fact and its source on the back of each pin. Streaks count nights, not taps. A home-screen widget carries tonight's Moon and what is worth finding, and a reminder can nudge you at dusk. All of it offline, no account, nothing sent, bought once.
Coming soon to the App Store
What it is
Sky looks at tonight's sky from where you are standing and picks three things worth walking outside for — the Moon at its phase, the best-placed bright planet, and a shape or a bright star in season, with a meteor shower added on its peak night and a close pair of planets added rather than swapped in. Nothing that has already set is ever offered, and nothing under ten degrees, because that is the trees and the rooftops. Then you go out, hold the phone up and swing toward it: the ring tightens, and when you are on it the sky gives it up and an enamel pin drops onto your board.
Why we built it
Every other stargazing app hands you the whole sky and leaves you to find something in it, or it charges a subscription for a planetarium you open twice. This hands you three things and a reason, in plain words — where to look, and when — and it is honest about the times you should not bother: if the sky is not dark yet it says when it will be, and if fewer than three things clear the rooftops you get fewer things rather than a padded list.
Want one like this?
Sky is one of 27. We can build yours.
Every app on the shelf started as one honest problem, scoped small and built native, end to end. That’s exactly how we approach client work — designed, built and shipped, without the bloat.
