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Landers, California at astronomical dusk (20-second exposure)
Landers, California at astronomical dusk (20-second exposure)

Dusk occurs at the darkest stage of twilight, or at the very end of astronomical twilight after sunset and just before night.[1] At predusk, during early to intermediate stages of twilight, enough light in the sky under clear conditions may occur to read outdoors without artificial illumination; however, at the end of civil twilight (when Earth rotates to a point at which the center of the Sun's disk is 6° below the local horizon), such lighting is required to read outside.[2] The term dusk usually refers to astronomical dusk, or the darkest part of twilight before night begins.

Technical definitions

Civil, nautical, and astronomical twilight.[3] Dusk is the darkest part of evening twilight.
Civil, nautical, and astronomical twilight.[3] Dusk is the darkest part of evening twilight.

The time of dusk is the moment at the very end of astronomical twilight, just before the minimum brightness of the night sky sets in, or may be thought of as the darkest part of evening twilight.[4] However, technically, the three stages of dusk are as follows:

Gallery

See also

References

  1. ^ The Random House College Dictionary, "dusk".
  2. ^ a b "Rise, Set, and Twilight Definitions". USNO.
  3. ^ Van Flandern, T.; K. Pulkkinen (1980). "Low precision formulae for planetary positions". Astrophysical Journal Supplement Series. 31 (3): 391. Bibcode:1979ApJS...41..391V. doi:10.1086/190623.
  4. ^ "Full definition of Dusk".
  5. ^ "Dusk – Definition and Meaning". www.timeanddate.com.