Exact Time of Sunrise and Sunset

February 03, 2021


Photographer: Dario Giannobile
Summary Author: Dario Giannobile; Marcella Giulia Pace

The beautiful sunset shown above was photographed without using special filters or lenses to enhance its majesty. It was taken near the Capo Granitola Light House in Sicily, on August 21, 2020.

Near the horizon, the Sun passes through a dense layer of atmosphere that attenuates its brightness and makes it appear red/orange. But this dense layer also generates an apparent slowdown in the advancement of the solar disk towards the horizon, causing the time of sunset to be different from that reported in the almanacs that don’t take into account atmospheric refraction. The amount of time of the slowing down of a sunset, as well as the anticipation of sunrise, is different everywhere in the world. Of course, it also depends on the latitude where you live. At my latitude, the Sun delays its setting by about two minutes.

Defining this gap in time between the actual and apparent sunrise and sunset is essential for navigation purposes. Sailors who use celestial navigation know the importance of this definition. It’s as important as a GPS signal or the beam of light from a lighthouse.

Photo Details: Camera: Canon EOS 6D; Software: Adobe Photoshop 21.1 (Windows); Exposure Time: 0.0040s (1/250); Aperture: ƒ/8.0; ISO equivalent: 400; Focal Length: 283.0mm