The Southern Cross swings around the south pole of the sky like the hand of a clock.
Your answer
Choose your town and a time in the calculator at the top. This is where your reading appears: which way the Cross is leaning, how high Acrux stands above your horizon, and the hour it next stands upright. The sky dial below then turns to show you the same sky.
The Cross is the hand · the south celestial pole is the pivot · drag Time, Day or Year
The working
First find how far the sky has turned: local sidereal time, the star clock for your longitude. Each star's hour angle is that turn minus the star's right ascension. Place Acrux and Gacrux around the pole by their hour angles, and the hand is the line from one to the other, measured clockwise from the top.
9:00 pm Monday 2 November at 151.21° longitude: star time 22.86 h (342.9°). Acrux hour angle 342.9° − 186.65° = 156.3°. The arm from Acrux to Gacrux points 150.0°, ÷ 15 = 10 on the ring.
Good to know
Questions
The whole southern sky wheels around one fixed point, the south celestial pole, once every 23 hours 56 minutes. The Cross is close to that point, so it swings around it like the hand of a clock. Note where its long arm points, and the same position comes round again a little under a day later.
The stars go round once in 23 hours 56 minutes, but our clocks run on the Sun, which takes 24 hours. So the Cross reaches each spot about four minutes earlier by the clock each night, which adds up to two hours a month and a whole day over a year. On this clock’s 24-number ring, the Hand of the Cross moves about one degree a night, or two numbers a month. That steady gain is what turns the clock into a calendar.
It depends how far south you are. South of 26.9° (Brisbane, Perth, Sydney, Melbourne, Auckland), Acrux at the foot of the Cross never sets. South of 32.9° (Sydney and everywhere further south), the whole Cross stays above the horizon all night, every night, though it can skim low over hills and trees.
Only from the tropics. Acrux rises above the horizon only south of 26.9° north, so Hawaii sees the Cross low in the south on spring evenings, and Miami barely glimpses its foot. From London, New York or Tokyo it never rises.
The hand runs along the long arm of the Cross, from Acrux at the foot to Gacrux at the head. Upright, with the head at the top, the hand reads 24. It turns clockwise as you face south: 6 when the head points west, 12 when the Cross hangs upside down below the pole, 18 when the head points east.
Follow the long arm from Gacrux through Acrux and keep going about four and a half times its length. That empty patch of sky is the south celestial pole. Drop straight down from it to the horizon and you are facing due south. The two bright Pointers beside the Cross help you pick the real Cross from the larger, dimmer False Cross.
The sky dial runs on the Sun at your longitude, not on the time zone, so noon is when the Sun is highest. The calculator above uses your ordinary clock time and does the conversion for you, which is why the two can differ by up to an hour or so.
Printout
The ring with all twelve month markers for Sydney NSW, and a table of the hand at midnight and the upright time on the first of each month. Take it outside on a clear night and check it against the real sky.
Face south. The hand runs from Acrux (foot) to Gacrux (head); 24 is upright. Printed 2 November 2026.
| Month begins | Hand at midnight | Upright at |
|---|---|---|
| 1 January | 16.9 | 7:05 am |
| 1 February | 18.9 | 5:03 am |
| 1 March | 20.8 | 3:13 am |
| 1 April | 22.8 | 1:11 am |
| 1 May | 1.8 | 10:13 pm |
| 1 June | 3.8 | 8:12 pm |
| 1 July | 5.8 | 6:14 pm |
| 1 August | 7.8 | 4:12 pm |
| 1 September | 9.9 | 2:10 pm |
| 1 October | 11.8 | 12:12 pm |
| 1 November | 12.9 | 11:06 am |
| 1 December | 14.8 | 9:08 am |
All night, every night: the whole Cross never sets from Sydney NSW. calculationtime.com/southern-cross-clock/
Why this exists
I first read the Cross this way while living aboard my yacht at Port Stephens. Checking it from the deck through an evening, I could see it keep pace with a 12-hour dial at half the speed of the hour hand. This page is that habit turned into a working clock you can use from anywhere in the southern sky.
Sources