The Types of Twilight

·

Totem Pole formation - Monument Valley

Early Civil Twilight at Monument Valley

I had a request to our support email recently, asking if we could explain in layman’s terms what the different twilight times meant. In the past, we’ve also received requests to include times of “Blue Hour” or “Golden Hour” in TPE. The problem with those terms is that they have no strict definition, so we’d need to adopt our own definition in order to calculate times.

Better instead to use Civil, Nautical and Astronomical twilight, which are well defined terms. In the help file for TPE on iOS/Android, twilight times are described as follows:

Twilight times

Times of civil, nautical and astronomical twilight are shown. The different twilight times are defined as follows:

  • Civil: when the sun lies 0° – 6° below the horizon
  • Nautical: when the sun lies 6° – 12° below the horizon
  • Astronomical: when the sun lies 12° – 18° below the horizon

Note: not all twilight phases occur in all locations/times – for example, the sun may never set far enough for there to be an astronomical twilight phase at northern latitudes in summer.

Accurate, but possibly insufficient to understand how you would leverage this information in your photography.

TPE for Desktop includes a glossary of terms, which describes each twilight phase as follows:

Civil twilight:

Civil twilight is defined as the period when the sun lies between 6 and 0 degrees below the horizon.
Of the celestial bodies, only the brightest stars and planets remain visible during civil twilight. Illumination is bright enough to distinguish objects in the landscape.

Nautical twilight:

Nautical twilight is defined as the period when the sun lies between 12 and 6 degrees below the horizon.
At this time, stars remain visible in the sky for navigational purposes and objects on the horizon are only just visible.

Astronomical twilight:

Astronomical twilight is defined as the period when the sun lies between 18 and 12 degrees below the horizon. At this time, point light sources such as stars remain visible in the sky, but fainter objects such as nebulae and galaxies are no longer visible. The majority of observers would consider astronomical twilight to be effectively dark.

This gives a few more hints, but for the purposes of most landscape photographers, I think we can sum things up even better.

When to be there

In general, be there for the start of civil twilight. (Or until the end of – you get the idea…)

The start of civil twilight is when you will start to see some real colour in the sky, with a mix of the deep blues and intense oranges as in the photo from Monument Valley, shown above.

As civil twilight progresses towards sunrise, depending on cloud coverage and height, you may see spectacular pinks and reds develop.

What about Nautical and Astronomical Twilight?

For most photographers, these are less relevant. In general, you’ll need to be using far longer exposure times during nautical and astronomical twilight.

Often as not, landscape shots taken during these times will include one or more night sky objects, such as the moon or planets during nautical twilight, or stars (but not deep space galaxies – see above) during astronomical twilight.

Remember also, that you can make silhouette images during nautical twilight: the sky is bright enough to see the outline of landforms on the horizon, but not (with the naked eye) to make out detail in the landscape.

Enjoy your twilight shooting!


If you’ve enjoyed this post, you might also enjoy “Understanding Light with The Photographer’s Ephemeris” co-authored with renowned landscape photographer Bruce Percy. It’s available through Bruce’s web-site.