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Civil, Nautical, & Astronomical - What are the Reasons?

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 97.124.76.228 (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 195.137.63.170 (talk) 08:01, 18 February 2014 (UTC)

Interesting question. As far as I can see from http://astro.ukho.gov.uk/nao/miscellanea/birs2.html, 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)

Shrunk the Gallery

I thought the gallery was getting out of control, so I deleted and replaced, and moved around some shots, and cut the Gallery to one line. Any of you whose photos didn't make the cut, I promise you that I removed at least as many of my own shots as others when editing. If you want to scream at me, this is the place...:-)→Pocketthis (talk) 17:52, 30 May 2015 (UTC)

Article contradicts itself on twilight definitions

Diagram shows twilight as...

Civil Twilight: Sun 0-6º below the horizon

Nautical Twilight: Sun 6-12º below the horizon

Astronomical Twilight: Sun 12-18º below the horizon

The text in the article shows twilight as...

Civil Twilight: Sun 0-6º below the horizon

Nautical Twilight: Sun 0-12º below the horizon

Astronomical Twilight: Sun 0-18º below the horizon

The diagram is right, not the text. See this article by Cambridge University.

http://www.ast.cam.ac.uk/public/ask/2445 Appple (talk) 01:30, 20 August 2015 (UTC)

See Bowditch's The American Practical Navigator, pp. 227-228 & table 1516, which agrees with the definition as given in the text. AstroLynx (talk) 14:16, 11 August 2015 (UTC)

Further note that the Cambridge web article cited above does not cite a reliable source but only WP (circular reasoning). AstroLynx (talk) 14:20, 11 August 2015 (UTC)

The American Practical Navigator is a good source you have there. It's possible that it's right. It shows twilight as...

Civil Twilight: Center of sun 0º50' - 6º below the horizon

Nautical Twilight: Center of sun 0º50' - 12º below the horizon

Astronomical Twilight: Center of sun 0º50' - 18º below the horizon

However, the Glossary of Marine Navigation which is put out by the same agency says differently.

http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Gloss-1.pdf#22

“ civil twilight. . 1. The period of incomplete darkness when the upper limb of the sun is below the visible horizon, and the center of the sun is not more than 6° below the celestial horizon.”

http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Gloss-1.pdf#82

“ nautical twilight. . 1. The time of incomplete darkness which begins (morning) or ends (evening) when the center of the sun is 12° below the celestial horizon. The times of nautical twilight are tabulated in the nautical twilight are tabulated in the Nautical Almanac; at the times given the horizon is generally not visible and it is too dark for marine sextant observations. See also FIRST LIGHT.”

http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Gloss-1.pdf#9

“ astronomical twilight. . 1. The period of incomplete darkness when the center of the sun is more than 12° but not more than 18° below the celestial horizon. SEE ALSO CIVIL TWILIGHT, NAUTICAL TWILIGHT.”Appple (talk) 01:30, 20 August 2015 (UTC)

Evidently, there is much confusion about the definitions (even among those who should know). Perhaps it is best to mention this in the article, the reader can then decide which definition s/he finds most practical. AstroLynx (talk) 11:21, 16 August 2015 (UTC)

That sounds like a good plan.Appple (talk) 01:30, 20 August 2015 (UTC)

@Appple please sign your postings by typing four tildes at the end so that I know to whom I am responding. AstroLynx (talk) 08:06, 17 August 2015 (UTC)

Article updated with both definitions. Appple (talk) 03:09, 20 August 2015 (UTC)

As I mentioned earlier, the Cambridge reference ("Ask an Astronomer") is not reliable as it refers to WP as source - so what you have here is circular reasoning. Either substitute it with an another verifiable source or leave it out all together. AstroLynx (talk) 07:48, 20 August 2015 (UTC)

In addition, the "Glossary of Marine Navigation" which you cite for the other definition of twilight is the appendix printed at the end of the "American Practical Navigator". Apparently, the authors of the glossary did not check their facts with the information in the earlier chapters of the manual. AstroLynx (talk) 07:59, 20 August 2015 (UTC)

@AstroLynx: Why haven't you removed or at least tagged the unreliable source(s)? Readers and editors should be made aware of the sourcing problems. --Florian Blaschke (talk) 15:25, 22 September 2015 (UTC)

I already mentioned in this section that some of the sources used by Appple were unreliable. In the mean time I have been looking at some other twilight-related sources but have not yet decided how best to correct the current text. Please feel free to do so yourself if you cannot wait. AstroLynx (talk) 15:35, 22 September 2015 (UTC)

Restore "In Religion" section

An argument could be made to restore the "In Religion" section. This section was here for a while with no problem, until I expanded the part about how twilight is used in Christianity. The whole section was then removed because "This is an encyclopedia article about the technical aspects of, and the defining "Twilight"." But, I would argue that a high level encyclopedia article is about the notion of a thing. Just like the article for the "Sun" has a religious aspects section, so too, the twilight article warrants one. It's simply further information related to twilight. The notion of twilight isn't limited to its technical aspects. — Preceding unsigned comment added by Matt1618 (talk • contribs) 18:03, 24 March 2016 (UTC)

• Totally disagree. I was going to pull the religion section months ago, but have been busy with other projects. This article has slowly been turning into an excuse to pitch religious beliefs. Misplaced Pages educates the reader about science. Lots of things happen at twilight. We don't mention them all because this venue isn't the place for it, and there isn't enough gig space in the universe for all of it. The important things that do happen at twilight, other than plenty of folks sitting down for dinner, have their own articles. My suggestion is to go to the Christianity article, and write about Christian activities that occur during twilight. It will then be in the right place. Please don't take any of this personally my friend, but this isn't Bible class. It's Misplaced Pages. That section ABSOLUTELY does not belong in this article. This article is not the place for those preaching God, and that's just what that section was doing. This isn't the first article I've removed religious sales pitches from, and it won't be the last. Religious sections belong in religious articles. It would be like going to the Sun article, and mentioning that lots of people go to church when the sun is out. Then we will find in the the night article saying: "Lots of folks pray during the night". Also, you can't use the Sun article as a comparison, because the Sun was actually thought of "as a God" in ancient times, and that is the reference to it in the article. Apples and Oranges. Subject closed.-Pocketthis (talk) 18:29, 24 March 2016 (UTC)

I hear ya. I'm not a zealot or a fanatic or anything. I didn't intend to hijack the article for preaching purposes just to expand on how twilight is significant in the Christian arena. Misplaced Pages educates the reader "period" not just "about science." Going around taking out religious-related material seems a bit anti-religious. It's relevant information to the topic at-hand. Now, if it was blatant proselytizing, I would agree, that it's not proper. Perhaps there is a compromise? I could trim what I submitted to make it simpler, more directly related? I come with good will, with an open mind to your argument. But "subject closed" kinda shuts down the "Talk" doesn't it? Matt1618 (talk) 21:20, 24 March 2016 (UTC)

• "Wiki educates people period" is the only thing we agree on. Thing is, Wiki educates people in the correct article. The article designed and created to educate the reader about the specific subject he is looking for. I wouldn't be going to the Christianity article to expand on the science of Twilight, just because I heard there was a paragraph there that dealt with what Christians do at twilight time. The subject is "CLOSED" because this is Misplaced Pages's protocol, and I've been helping enforce it for 5 years. You don't come with good will. You come with religion. You are a religious person. A person of faith. Please feel free to contribute to in the articles written by those who also live their lives on faith and not fact. No compromise. I'm sorry, take it where it will be appreciated. There isn't a religion in the world that doesn't have something going on at different times of the year, and all times of the day. Have fun writing about that in the articles designed to expand on them. Happy editing.Pocketthis (talk) 00:53, 25 March 2016 (UTC)

"You don't come with good will. You come with religion." Wow... so religious people are inherently ill-willed? I live by faith and fact. Faith and Reason are entirely compatible - but, this isn't the place for a discussion on that. I'm just sorry, as a relatively new contributor to wikipedia, to find people on here who squash relevant information just because it is religious in nature. "Articles must represent all significant views fairly, proportionately, and without bias." Matt1618 (talk) 06:15, 25 March 2016 (UTC)

And really all you had to say was, "Hey man, if you'd like to keep the 'In Religion' section, would you mind carving it out into a separate article? Then those who are interested can follow a link and those who aren't can ignore it" and I would have said, "Oh... yeah, sure, no problem." I'm creating a "Twilight (Religious use)" article now. Hopefully you won't mind my simply putting a link to it in the main article. Matt1618 (talk) 06:55, 25 March 2016 (UTC)

• This isn't the front gate at someone's home where you can leave a Watchtower, and those that are interested can read it, and those that aren't can throw it away. This isn't the inside of someone's home where you can pop up on the TV screen begging for dollars, promising the sick, the old and the poor redemption, simply by sending in their life savings. The answer is no. No links. No Carving a new article. No. Take it to the Christianity article, and I'm sure you'll have no problem finding interested people to read your new section on how twilight is special for Christians during certain "Holy" times and activities. It's really simple: Think of the encyclopedia Science Articles as you would a Public School. You can't pray here. Now think of the religious articles as your church. Keep it where it belongs, and all is good. -Pocketthis (talk) 15:50, 25 March 2016 (UTC)

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