Star Watcher
Identify stars, planets, constellations, meteor showers and deep-sky objects for any date, ranked for your sky and kit, with cloud and rain.
Will you see anything?
Best things to look at
Everything above the horizon
Part of the sky is permanently shut to you, and only your latitude decides which
A star's highest point above your horizon is 90° − |latitude − declination|. Set that to zero and everything follows: from latitude L a star never rises if its declination is below L − 90, and never sets if it's above 90 − L. From 40° north, nothing below declination −50 ever comes up — not at any hour, on any night, in any year. Not "hard to see." Never above the horizon.
| Latitude | Nothing below | Stars that never rise | Stars that never set |
|---|---|---|---|
| 51.5°N | dec -38.5 | 19 of 102 (18.6%) | 28 |
| 40°N | dec -50 | 13 of 102 (12.7%) | 18 |
| 30°N | dec -60 | 4 of 102 (3.9%) | 8 |
| the equator | dec -90 | 0 of 102 (0.0%) | 0 |
| 33.9°S | — | 12 of 102 (11.8%) | 11 |
The equator row is the point of the exercise. Stand on it and the whole catalogue is available across a year, with nothing permanently up and nothing permanently gone. Move away in either direction and you start trading one pole's sky for the other's — both columns grow together.
From 40° north the losses include Canopus, the second-brightest star in the sky, along with Achernar, Hadar, Acrux, Mimosa, Gacrux, Miaplacidus and 6 others. Of the 15 constellations drawn here, exactly one is wholly out of reach — Crux, the Southern Cross — while Cassiopeia and Ursa Minor never set at all.
The detail worth noticing is that no constellation is partly cut at that latitude. All 15 are entirely up or entirely gone. Constellation figures are compact enough in declination that a horizon drawn at −50 doesn't bisect any of them, which is why the sky from one place feels like a fixed set of shapes rather than a collection of fragments.
Checking the maths against something you can verify without a computer
Coordinate conversion is easy to get subtly wrong, so it's worth testing against a fact anybody can check with a protractor: the altitude of Polaris equals your latitude. Running this tool's own conversion, it does — at every latitude tried, to within 0.08 of a degree.
| Latitude | Computed altitude of Polaris | Error |
|---|---|---|
| 51.5°N | 51.58° | +0.08° |
| 40°N | 40.08° | +0.08° |
| 25°N | 25.08° | +0.08° |
That residual isn't error — it's Polaris. The star sits at declination 89.264, which is 0.74° off the true pole, so over a day it traces a small circle rather than holding still. Measured hour by hour its altitude swings 1.46° — very close to twice the polar distance (1.47°), which is exactly what a circle of that radius should give. The check and its own discrepancy both come out right.
Two more that need no catalogue at all. The Sun's declination comes out 23.44° at the June solstice and -23.44° at the December one, matching the 23.44° tilt of the Earth's axis and symmetric to a hundredth of a degree. And the Moon, whose orbit is inclined to the ecliptic, ranges from -28.3° to 28.2° across a year — wider than the Sun ever goes, and still inside the band its orbit allows.
The catalogue behind all this is 102 naked-eye stars — the faintest is magnitude 4.01, the brightest Sirius — joined by 51 line segments across 15 constellations, with every endpoint checked to be a star that actually exists.
How to use
- Set your location, or press Use my location.
- Pick a date and time, or press Tonight. The whole page — sky, forecast and recommendations — follows that moment.
- Read Best things to look at for a ranked shortlist, then use the map to find them.
- On a phone, press Point at the sky and hold the phone up. On a computer, drag the sky to look around.
Frequently asked questions
Can I check a different night?
Yes. Set any date and time and the star map, the Moon phase, the darkness window and the recommendations all move with it. Use the day arrows to step forward or back, or press Now to return to the live sky.
Does it tell me if it is going to rain?
Yes, and rain takes over the headline when it is forecast — reading "mostly clear" next to actual rain would look like a broken forecast. It also says roughly when overnight rain starts and how long it lasts, because that decides whether you get an hour out before it arrives. Snow is named as snow rather than lumped in with rain.
What do the bars mean?
One bar per hour of the chosen day, shaded darker for more cloud. The night hours are drawn taller, and any hour with rain or snow is drawn blue, so the shape of the night reads at a glance. Hovering a bar gives the exact figures.
How far ahead does the cloud forecast go?
About 16 days, which is the limit of the underlying weather model. Past that the page says so rather than showing a prediction that would be meaningless.
Why does the ISS disappear when I change the date?
Because its position comes from a live tracking feed that only knows where the station is right now. Drawing it against a future night would look convincing and be wrong, so it is hidden instead.
Why is the night average cloud figure different from the headline one?
The headline is the cover at the exact hour you chose. The night average covers roughly 8pm to 4am, because one clear hour in an otherwise solid night is not a night worth planning around.
Does it know about meteor showers?
Yes, all twelve major annual showers. It says which are active on your chosen date, how far from peak they are, and roughly how many an hour to expect — rates fall off sharply either side of maximum, so a shower five days out is a genuinely different proposition from the same shower on its night.
Why does it ask what my sky is like?
Because recommending the Andromeda Galaxy to someone in a city centre is bad advice. Deep-sky objects each carry the darkest sky they survive, so a city setting keeps the clusters and nebulae that punch through and drops the galaxies that do not.
Why does it ask what equipment I have?
A telescope target is useless if you are standing outside with nothing. Setting it to your eyes alone shows only what is genuinely visible unaided; binoculars open up most of the clusters; a telescope adds the planetary nebulae and galaxies.
What is the darkest window?
The stretch that is both astronomically dark and free of the Moon, which is the only time faint objects are really reachable. It is the most useful line on the page — "a bright Moon ruins tonight" and "you have from 1:20am" describe the same sky but lead to completely different evenings.
What is red night mode?
It tints the whole page red on black. Looking at a white screen costs you roughly twenty minutes of dark adaptation every time, which is exactly why astronomers use red torches. Turn your screen brightness down as well.
Does it remember my location?
Yes — your place, sky quality, equipment and night mode are stored in your own browser and nowhere else. Nothing is sent anywhere.
Are constellations included in the recommendations?
Yes, ranked alongside the planets and bright stars, each with the landmark that finds it and the one thing in it worth looking at — the Orion Nebula, the Andromeda Galaxy, Albireo in Cygnus. A pattern is only suggested once most of it has cleared the horizon, because half a constellation is not something anyone can recognise.
Why did a constellation I can see not get recommended?
Either part of it is still below the horizon, or the Moon is bright and the pattern is a faint one. Orion and the Plough shine through almost anything; Andromeda and the Little Dipper genuinely disappear under a full Moon, so they get demoted rather than suggested and then disappointing you.
What makes something a top recommendation?
Brightness, how high it sits, and how time-critical it is. Altitude matters more than people expect — an object at 10 degrees is seen through about five times as much atmosphere as one overhead. A bright Moon also demotes faint stars, because it genuinely washes them out.
Does the Moon phase matter that much?
For faint objects, more than anything except cloud. A full Moon floods the sky and is itself flat and glary in a telescope; a crescent or quarter shows crater shadows along the terminator, which is the best detail of the month.
Does it work on a computer?
Yes, but computers have no compass, so pointing does nothing. Drag the sky to look around instead — the tool detects this and tells you rather than appearing broken.
How accurate is it?
Star positions are precise. The limit is your phone compass, which is typically several degrees out and is thrown off by metal and magnets — good enough to find a constellation, not to aim a telescope.
What does it need from the internet?
The live ISS position, the cloud forecast, and geocoding if you type a city. Stars, planets, the Moon and the darkness times are all computed on your device.
🌐 This tool looks up results using the ISS tracking service and the cloud forecast. The word you enter is sent to that service to fetch results; nothing is stored by this site.