The Milky Way and its centre: when and where to look
The pale Milky Way band circles the whole sky, and its brightest stretch points towards the centre of the Galaxy. When the centre rises, in which direction and how high it climbs depend on your city, the date and the clock. Being above the horizon is not enough: the sky must be fully dark, and moonlight and light pollution must not drown it out.
What are the Milky Way band and the galactic centre?
The Milky Way band is the light of countless distant stars in our galaxy's disc, seen from inside it, and it circles the whole sky. The galactic centre is the direction of the Galaxy's middle, in Sagittarius, about 26,000 light-years away. Interstellar dust blocks its visible light, so the dot on the chart marks a direction, not a star you can see.
When and where do I look for the centre on a given night?
Pick a city and a date and move the clock: from the northern hemisphere the centre rises in the south-east, is highest near due south and sets in the south-west; from the southern hemisphere it passes high in the north. It arrives about four minutes earlier each day, roughly two hours a month, and the further north you are, the lower it climbs.
Why might it still be invisible when it is above the horizon?
The Sun also has to be 18° below the horizon for astronomical darkness, and the centre is best clear of the thick air near the horizon; this lesson uses 10° as a teaching reference. Where the two overlap is a geometric candidate window, but cloud, moonlight, light pollution, terrain and dark adaptation still decide what you see.
Find the direction of the centre, then check the dark
The faint band of light across the night sky is the Milky Way. Its brightest, broadest stretch points towards the centre of the Galaxy, and when and where that stretch appears depends on your city and the clock. Find it first, then check whether the sky is dark enough.
What the band is
The Milky Way band is our own galaxy seen from inside its disc. The Sun sits in a flat disc of stars; look along the disc and countless distant stars pile up into a pale band that runs all the way round the sky.
The widest, brightest stretch lies in Sagittarius and Scorpius, the direction of the galactic centre. The pink dot on the chart marks only that direction: dust hides the centre itself, and what the eye sees there are star clouds in front of it.
In one night, the centre moves
Earth's rotation makes the galactic centre rise and set like any star. Pick a city and a date and move the clock on: from northern latitudes it rises in the south-east, is highest near due south and sets in the south-west.
The lab tracks the Sun too. Only when it is 18° below the horizon is the sky astronomically dark. If the centre rises before the sky is dark, or sinks low before dawn, that stretch does not count as a candidate.
Change the month, change the city
Hold the clock at 9 pm and change only the month: the centre reaches the same place about two hours earlier each month. From Taipei it is hardly up after dark from November to January, waits until the small hours in February and March, and is there as soon as it is dark in June and July.
Hold the date and clock and change only the city: the further north, the lower the centre climbs. From London it peaks at about 9.5°, short of even the lab's 10° reference line; from Sydney it passes almost overhead. Seasons are reversed between hemispheres, so the lab names months instead.
A computed window still needs the real sky
A candidate window says two geometric things: the sky is dark and the centre is not too low. A Moon above the horizon washes out the faint band, but once a bright Moon has set it no longer lights the sky directly.
Cloud, haze, light pollution, hills and whether your eyes are dark-adapted are not in the calculation. Photographs usually show a more colourful Milky Way than the eye does, because the camera gathers light for a long exposure. Check the stargazing planner and dark-sky sites before you go.
Pick a city and a night, then find the centre
The chart draws the Milky Way band from a local catalogue, and the pink dot marks the direction of the galactic centre. The timeline below puts the centre's altitude, astronomical darkness and the Moon for the same night together. Each mode changes just one thing.
City and night stay fixed; only the time changes (local noon to the next noon).
City and local clock time stay fixed; only the month changes, always on the 15th.
Local date and clock time stay fixed; only the city changes, each in its own time zone.
The pale broad band is the Milky Way; the pink dot marks only the direction of the galactic centre, not a star. The arc along the bottom is the horizon.
Sampled every five minutes, with each boundary refined to about a minute; times are in the chosen city's time zone. Altitudes are geometric, without refraction.
No candidate window tonight: the Sun never gets 18° below the horizon, so the sky never becomes astronomically dark.
No candidate window tonight: the centre never climbs above the 10° reference line during this night. Other parts of the Milky Way band may still be up.
No candidate window tonight: the centre is above 10° only in daylight or twilight, apart from astronomical darkness. Other parts of the Milky Way band may still be up.
What to check before you go
The lab computes geometry only. Cloud, transparency and haze, light pollution, hills and buildings, moonlight, and the twenty to thirty minutes your eyes need to adapt to the dark are all left out. To the eye the Milky Way is a grey-white band; the colour and detail in photographs come from long exposures.
The galactic centre is Sagittarius A* at J2000 (RA 17h45m40s, Dec −29.0°), the same point as the site's sky map. Cities use their centre coordinates, and the horizon is a smooth geometric 0° with no refraction, elevation or terrain.
In “Through one night”, pick Taipei on 15 July and move from 18:00 to 04:00 the next day. Note when the centre clears 10° and when astronomical darkness begins; only the overlap is a candidate window.
Switch to “Compare months”, keep Taipei at 21:00 local time and step from January to October. Watch the centre go from below the horizon, to a pre-dawn object, to up as soon as it is dark. Then try Sydney, and do not carry northern season names across.
Switch to “Compare latitudes”, keep one date at 21:00 local time and press London, Seoul, Tokyo, Taipei, Singapore and Sydney in turn. Compare the “highest point in darkness” under the timeline: the further north, the lower it gets, and London never reaches 10°.
Our galaxy, seen from inside its disc
The Milky Way is a flat disc of stars with a central bulge, and the Sun lies roughly halfway out from the centre. Look along the disc and your line of sight crosses the most stars, so their light piles up into a band; look out of the disc and the stars thin out. The band therefore runs right round the sky; it is not something that appears only in one season.
The plane of the Milky Way is tilted about 63° to the celestial equator and about 60° to the ecliptic, so it crosses the sky at a slant that keeps changing against the horizon. On northern winter evenings you see the fainter stretch facing away from the centre, through Perseus and Auriga; the stretch towards the centre, in Sagittarius, is broad and bright.
Why the centre is not a bright point
The centre marker uses the position of Sagittarius A*, about 26,000 light-years away. NASA notes that our view towards the centre is heavily blocked by clouds of gas and dust; astronomers study it in infrared, radio and X-rays, or through gaps with less dust, such as Baade's Window.
What the eye and the camera call the “core” of the Milky Way is really star clouds in front of the centre, such as the Sagittarius Star Cloud. The Great Rift, running from Cygnus to Sagittarius, is foreground dust hiding the starlight behind it. So the pink dot is a direction; on site you look for the brighter, broader stretch of band around it.
Moving in a night, earlier each month
Relative to the stars, Earth turns once in about 23 hours 56 minutes, so the centre reaches the same position about four minutes earlier each day, or about two hours a month. The month experiment holds 21:00 fixed to show that drift adding up.
Around 19 December the Sun lies almost in the same direction as the centre, which then spends the whole day in the daytime sky; by mid-June the Sun lies in the opposite direction, and the centre rises at nightfall and is highest around midnight. For Taipei in 2026, mid-February has to wait until about 03:50, mid-July is a candidate as soon as it is dark (about 20:14), mid-October has only about 18:44–20:09, and November to January have no candidate window.
Latitude sets how high it climbs
The centre's declination is about −29.0°. At northern latitude φ its greatest altitude is about 90° − (φ + 29.0°): about 60° from Singapore, 36° from Taipei, 25° from Tokyo, 23° from Seoul and only about 9.5° from London. In the southern hemisphere, from Sydney, it reaches about 85°, almost overhead.
Light from low in the sky passes through more air, where haze, water vapour and the glow of distant towns gather, and hills and buildings block it first. That is why this lesson uses 10° as a teaching reference. It is not a physical cut-off: from a mountain with an open view you might see it at 8°, while over a humid lowland it can look faint at 20°.
Astronomical darkness, the Moon and contrast
Only when the Sun is 18° below the horizon does sunlight scattered in the upper atmosphere all but disappear; this is astronomical darkness. The Milky Way band is far fainter than a bright star, and in civil or nautical twilight the sky background is still too bright, so the candidate window uses astronomical darkness only.
The Moon needs two separate questions: is it above the horizon, and how much of it is lit? A full Moon up all night drowns the Milky Way, but once the Moon sets the sky goes dark again, however much of it is lit. The lab lists when the Moon is up and how much is lit separately, rather than folding them into one score.
Where this model stops
The lab uses city-centre coordinates, a geometric horizon and altitudes without refraction, and finds window edges to about a minute. Weather, transparency, light pollution, terrain, elevation and the observer's eyes are not in it, so it never tells you that you will definitely see or photograph the Milky Way.
Photographs often show more colour and detail than the eye: the camera gathers light over a long exposure, while the eye sees a grey-white band with dark lanes. To decide whether a night is worth going out, take the candidate window to the stargazing planner for cloud and moonlight, then use the dark-sky pages to pick a place away from lights with an open southern view.
FAQ
Can you only see the Milky Way in summer?
No. The band circles the whole sky, so part of it is in the night sky in every season. What changes with the season is when the brightest stretch, towards the galactic centre, is up at night. From Taipei it is visible before dawn from February, up as soon as it is dark in June and July, and barely visible after dark from November to January. The months differ again in the southern hemisphere.
Once the galactic centre is above the horizon, can I see it?
Not necessarily. The Sun must be 18° below the horizon for astronomical darkness, the centre is best clear of the thick air near the horizon (this lesson uses 10° as a teaching reference), the Moon should be down or a thin crescent, and the sky must be clear and away from light pollution. Even then the eye sees a grey-white band; the colour in photographs comes from long exposures.
What is the galactic-centre dot on the star chart?
It marks the direction of the centre of the Milky Way, Sagittarius A*, about 26,000 light-years away. Interstellar dust blocks the centre's visible light, so that point itself cannot be seen; the bright “core” you see on site is star clouds in front of it, around Sagittarius.
The Milky Way layer comes from the site's d3-celestial data; the galactic centre is Sagittarius A* at J2000, and the Sun and Moon use NOAA and Meeus approximations. The results are geometric positions, not a visibility forecast.