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Civil, Nautical, & Astronomical - What are the Reasons?[edit]

What is the purpose for the three different "versions" to twilight? The article mentions that nautical twilight is used in military planning; but is that it's origin? If so, what about the other two? Any addition of this info would greatly help both me, and the article in general. — Preceding unsigned comment added by (talk) 19:23, 4 May 2013 (UTC)

Civil twilight is bright enough that normal daytime activities can be performed without additional lighting. For example, a car can be driven safely without using its headlights. Many jurisdictions have laws that compel drivers to turn their headlights on at civil dusk. Defining the time when this occurs is therefore necessary for the implementation of these laws.
Nautical twilight is essentially bright enough to allow a ship to be navigated safely without relying on navigational aids such as lighthouses. In warfare, lighthouses cannot be relied on, so planners must ensure that activities will occur when nautical twilight is present.
Viewing very faint astronomical objects such as distant galaxies can be done only if the sky is almost perfectly dark. Knowing the times of astronomical dusk and dawn allows astronomers to plan their activities appropriately.
DOwenWilliams (talk) 20:00, 4 May 2013 (UTC)
The reference given is a US one. Are these 3definitions US only, or are they recognised internationally? I'vebeen a seaman for 40 years and never heard of them. In the UK lighting-up time is legally defined in terms of minutes after sunset, not solar elevation. The two methods will diverge widely during the year, especially in Shetland -User:Brunnian — Preceding unsigned comment added by (talk) 08:01, 18 February 2014 (UTC)
Interesting question. As far as I can see from, the British government uses the same definitions of the three kinds of twilight as we do here. There is also a period called "Hours of Darkness" which extends from 30 minutes after sunset to 30 minutes before sunrise. Laws concerning use of car headlights, etc., are written in terms of hours of darkness. DOwenWilliams (talk) 21:53, 18 February 2014 (UTC)

Beginning and end of the various twilights[edit]

Quote: "Nautical twilight is defined to begin in the morning, and to end in the evening, when the center of the sun is geometrically 12 degrees below the horizon." It seems like it begins in "the morning", lasts the whole day, and ends in the evening at a specified sun angle. Same with astronomical twilight.

It is not explicitly stated in the main sections for nautical twilight and astronomical twilight when they end in the morning and when the begin in the evening. It is possible for a reader like me to wonder whether nautical twilight in the evening starts at sunset or at civil dusk, etc.

I suggest that these problems can be solved by writing out fully in the sections for nautical and astronomical twilights when they begin and when they end.

Gbwi (talk) 12:22, 5 October 2013 (UTC)

Possible photo[edit]

Possible photo for twilight.

For possible inclusion in article.--Tomwsulcer (talk) 13:01, 22 December 2013 (UTC)

  • Hello Tom. I also am a boomer (read your user page), and made a living as a photographer for the past 35 years. You have some nice photos on your user page, I enjoyed looking at them. In the case of this photo, in my opinion you have a "Dusk" photo. Hard to get because of the lighting. Also, the composition of the photo needs some editing. If you still have the original, balance the photo by coming lower, and showing the base of the garage. There will still be plenty of sky left to see. Also, spin the photo so the objexts sit at 90 degrees to better balance it, by simply making sure the base of the garage is perfectly horizontal. Then, put it in the Dusk discussion page, and we'll have another peek at it. Thanks-Pocketthis (talk) 17:53, 22 December 2013 (UTC)
    • Hey thanks Pocketthis. I deleted the original (actually in my computer trash bin but it would take me an hour to search through). Or maybe I'll try to redo the shot when lighting is similar outside. Cool you're a photographer; I'm only an amateur photographer but I carry my camera wherever I go and sometimes get some good shots. Good idea about Dusk page; I'll post on its talk page.--Tomwsulcer (talk) 18:50, 22 December 2013 (UTC) Btw just saw your user page. WOW -- great photos. You're a pro!--Tomwsulcer (talk) 18:52, 22 December 2013 (UTC) Also I'd like to post one of your photos on my user page here that is assuming you have no objections.--Tomwsulcer (talk) 19:07, 22 December 2013 (UTC)
      • Post away my friend, I'm flattered you'd like to display a photo of mine. You're not so bad yourself. My photos these days are far from technologically accurate. I sold all my pro equipment when I retired and just take 'point and shoots' with my digital Leica. I still strive for composition, which is just as important as the technical aspects of a photo. In fact, I think composition may be more important. Happy Holidays.-Pocketthis (talk) 23:54, 22 December 2013 (UTC)