Sun below −18° · next 30 nights

True darkness at Sutherland (SAAO)

Astronomical darkness starts only when the Sun is 18° below the horizon. These bars are calculated for the coordinates, so high-latitude nights correctly show no true darkness when twilight never ends.

Longest night8.3 h10 Oct

Nights reaching −18°30 / 30Astronomical darkness occurs

Longest window20:20–04:40Moonlight is shown separately in the planner.

Solar geometry, not a clock rule

Hours of astronomical darkness

10 Oct8.3 h0% moon

11 Oct8.3 h2% moon

12 Oct8.3 h6% moon

13 Oct8.3 h11% moon

14 Oct8.3 h18% moon

15 Oct8.3 h26% moon

16 Oct8.3 h34% moon

17 Oct8.3 h43% moon

18 Oct8.3 h53% moon

19 Oct8.3 h62% moon

20 Oct8.3 h72% moon

21 Oct8.3 h80% moon

22 Oct8.0 h88% moon

23 Oct8.0 h94% moon

24 Oct7.7 h98% moon

25 Oct7.7 h100% moon

26 Oct7.7 h99% moon

27 Oct7.7 h96% moon

28 Oct7.7 h91% moon

29 Oct7.7 h83% moon

30 Oct7.7 h73% moon

31 Oct7.7 h62% moon

1 Nov7.7 h50% moon

2 Nov7.7 h39% moon

3 Nov7.7 h28% moon

4 Nov7.7 h19% moon

5 Nov7.7 h11% moon

6 Nov7.7 h5% moon

7 Nov7.7 h2% moon

8 Nov7.3 h0% moon

8.3 hours

Use this as the outer boundary for faint-object work. Moon altitude, cloud and transparency will narrow the practical window. Add the Moon →

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Moon

Moonless nights

Find the longest uninterrupted dark windows.

Core

Milky Way

See when the galactic core clears the horizon after dark.

−18°

Astronomical darkness

Track true darkness, including polar twilight.