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How to Calculate Dusk

Dusk is the time at which the sun is six degrees below the horizon. It is also referred to as twilight or civil twilight. You can see objects but it is too dark to do most things outside. It is important not to confuse dusk and sunset, which is when the upper edge of the sun is on the horizon. Calculating dusk is useful so you know exactly how much time you have to run, garden, play outside or eat on the patio. You can check this quickly online, using dusk calculators.

Instructions

- 1
  Open the Sunrise and Sunset Calculator in your Internet browser (see Resources). Select your location from the drop-down list. If your location is not listed, select "Other Location" and choose a location from the pop-up window. Choose "See Sunrise/Sunset." On the next page, under "Columns," choose "twilight/rise/set (sun)" from the list and select "Show." The columns will tell you the start and end times for astronomical, nautical and civil twilight for the entire month. You can choose to show a different month or year from the options on the top bar.
- 2
  Open the U.S. Navy Sun and Moon Data site (see Resources). Enter the year, month, day, city and state. Then select "Get Data." The next page will tell you the start and end times of civil twilight as well as the moonrise and moonset times.
- 3
  Open the Gaisma website (see Resources). Click on the map displayed. Select your continent from the next page. Select your country, state and city. On the next page you can see dawn and dusk times, as well changes in day length, among other statistics.

Astronomy