Sun below −18° · next 30 nights

True darkness at Hilo

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 night10.7 h28 Nov

Nights reaching −18°30 / 30Astronomical darkness occurs

Longest window19:00–05:40Moonlight is shown separately in the planner.

Solar geometry, not a clock rule

Hours of astronomical darkness

2 Nov10.0 h33% moon

3 Nov10.0 h23% moon

4 Nov10.0 h15% moon

5 Nov10.3 h8% moon

6 Nov10.3 h3% moon

7 Nov10.3 h1% moon

8 Nov10.3 h0% moon

9 Nov10.3 h2% moon

10 Nov10.3 h5% moon

11 Nov10.3 h10% moon

12 Nov10.3 h16% moon

13 Nov10.3 h23% moon

14 Nov10.3 h31% moon

15 Nov10.3 h41% moon

16 Nov10.3 h50% moon

17 Nov10.3 h60% moon

18 Nov10.3 h70% moon

19 Nov10.3 h79% moon

20 Nov10.3 h87% moon

21 Nov10.3 h93% moon

22 Nov10.3 h98% moon

23 Nov10.3 h100% moon

24 Nov10.3 h99% moon

25 Nov10.3 h96% moon

26 Nov10.3 h90% moon

27 Nov10.3 h82% moon

28 Nov10.7 h72% moon

29 Nov10.7 h61% moon

30 Nov10.7 h49% moon

1 Dec10.7 h38% moon

10.7 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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−18°

Astronomical darkness

Track true darkness, including polar twilight.