Reading the Timeline Strip on Sunhour

If you have looked at sunhour, you have seen the horizontal timeline that runs across the sun page. It looks decorative at first; it is not. Each band is a different lighting state, and once you can read the strip at a glance you can plan any sun-dependent activity in about five seconds. Here is how to use it.

What the strip is showing

The strip represents 24 hours, from midnight on the left to midnight on the right. The vertical axis does not matter — it is a one-dimensional view of time. The colours represent the sun's state at each moment.

• Black bands: astronomical night. The sun is more than 18° below the horizon. Stars are visible to their faintest.
• Deep blue / indigo bands: astronomical twilight. The sun is between 12° and 18° below. Sky has the faintest gradient, deep dark blue.
• Mid-blue bands: nautical twilight. Sun is between 6° and 12° below. Horizon is no longer visible.
• Light blue / lavender bands: civil twilight. Sun is 0° to 6° below. Outdoor activities possible without artificial light.
• Gold / amber bands: golden hour. Sun is 0° to 6° above the horizon. The warm photography light.
• Pale yellow / white bands: daytime. Sun is above 6° altitude. Regular daylight, becoming harsh near solar noon.

The transitions between bands are the events: sunrise, sunset, civil/nautical/astronomical twilight start and end. Hover over (or tap) the strip and you see the exact clock time for that moment on that date.

The little markers

On top of the bands you will see a few labelled ticks: sunrise, solar noon, sunset, and the boundaries between twilight categories. Solar noon is usually the highest-altitude point of the day, and it is rarely 12:00 — see the post on solar noon for why.

The moon strip

Below the sun strip is a moon strip showing when the moon is up that day, and roughly its phase. A bright full moon is shown as a bright band; a new moon is faint or absent. This is critical for astrophotography because the question "is the sky actually dark right now" is the combination of "sun band" and "moon band".

How to plan a shoot in five seconds

Suppose you want to photograph blue hour in Berlin next Saturday. Open sunhour, set the date, scan the strip. The evening blue band sits between civil-twilight end and nautical-twilight end, somewhere around 19:30 to 19:55. Read the values; set your alarm for 19:00 to be on location and set up before the band starts. Done.

Same exercise for Milky Way astrophotography in Cape Town: scan for the black band, check that it overlaps with the moon strip being empty, write down the start and end. If there is no black band (because of high latitude in summer), the night is not dark enough — pick a different date.

The patterns to notice

After a few weeks of using the strip you will start noticing patterns.

• The width of the warm bands tells you your latitude effect. Wide gold bands = magic hour is long, you have time. Narrow = move fast.
• The presence or absence of a black band tells you whether the night is truly dark. At high latitudes in summer there is no black band at all.
• Solar noon position on the strip shifts with daylight-saving changes and your longitude inside the time zone. A solar noon at 13:20 is normal in central Europe in summer; the same time in winter at the same place would be 12:20.

The advantage over text tables

A sunrise/sunset table gives you specific times. The strip gives you proportions. Looking at proportions trains intuition. You start to feel "this date has a long blue hour" or "this date has barely any night" without checking the numbers. That is the difference between consulting an app and understanding the sky.

For comparison, NOAA's solar calculator gives the same data in tabular form. The maths is identical. The strip is just faster to read once you are used to it.

One trick: hold a finger across the strip

Cover the part of the day you cannot use (work hours, sleep hours, whatever). What is left is your available shooting window. Now you can see at a glance which lighting bands fall inside it. If your only free hours are 06:00 to 07:30 and the strip shows the golden band finishing at 06:25, you have a 25-minute photographic window followed by an hour of harsher light. Plan accordingly.

Once the strip is internalised, the photo planning question changes from "when is sunrise" to "what light do I want, and when does it happen for me". Better question; better answers.