Talk:Twilight

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[edit] Additions

I would like to see the addition of calculating all twilights (civil/nautical/astronomical) by hand given lat/long/altitude. I am not familiar enough with LaTex to do this myself at this point. —Preceding unsigned comment added by 82.127.87.189 (talk • contribs)

I am not sure why you would like to calculate this yourself. There are lots of astronomical and planetarium software that works out the timing automatically depending on location. I know of Astronomy Lab 2, Cybersky and Orbitron that generate this information. There are also a number of astronomical websites that can tell you this information eg. Heavens Above. - Shiftchange 00:52, 16 February 2006 (UTC)
There is one such calculator here [1]. Slowmover 19:36, 11 April 2006 (UTC)
Whether you can see a reason why someone would want to calculate it isn't relevant to whether or not it's an appropriate addition to the article. Given that up until such programs and websites became easily available, calculating the time for twilight was the only way to determine it. And if someone is writing a program that includes twilight calculations, an encyclopedia article on twilight is a reasonable place to expect to find the formula for doing so. CruiserBob (talk) 18:54, 27 November 2007 (UTC)

It looks like the Civil Twilight page material has been merged with Twilight, but the page still exists and the diambiguation page does not list it. I don't know how to fix this.--Fitzaubrey 04:18, 13 July 2006 (UTC)

I changed Civil twilight to be a redirect to this page. --Usgnus 05:00, 13 July 2006 (UTC)

[edit] Merge

Should this article be merged with dawn?

Oppose. Twilight and dawn are two different things, though related (provide links). However, I am for merging twilight with dusk. --HereToHelp (talk) 13:38, 27 November 2005 (UTC)

Oppose. Dusk and dawn are the times that evening twilight begins and morning twilight ends with. I would oppose twilight being merged into either dusk or dawn. Merging both of these topics into twilight would be more appropriate. - Shiftchange 10:07, 29 November 2005 (UTC)

Oppose. I agree with Shiftchange. I have just used Wikipedia to look up the definition of civil twilight. I would have been most dissapointed had I been redirected to dawn or dusk. Dawn and dusk refer to specific times. Twilight refers to a period of time. - Allen Oliver 18:42, 19 February 2006 (UTC)

Oppose per Allen Oliver. Bad idea. Civil twilight, nautical twilight, and astronomical twilight are specific terms with distinct meanings which would be lost with a merge into "dusk" or "dawn". - Sensor 03:42, 1 March 2006 (UTC)

Oppose per Shiftchange above. Dusk and dawn are terms for evening twilight and morning twilight respectively. Twilight is the usual scientific term. Dusk and dawn should be merged into Twilight. 204.101.243.169 16:36, 11 April 2006 (UTC) (logging in again to sign) Slowmover 16:37, 11 April 2006 (UTC)

Oppose Dawn and dusk are both twilight - before the sun rises, and after the sun sets respectively. Merging all three articles (dawn, dusk, and twilight) as a single article under "twilight" would be a good idea. 203.122.108.171 (talk) 17:17, 2 January 2008 (UTC)

[edit] Length of twilight

The length of twilight is also influenced by the time of the year as well (longer near the solstices). I'd like to see this topic treated better in this article.

68.183.119.26 17:52, 27 December 2006 (UTC) ngur

So would I, and I'd like a clearer explanation of why the length of twilight changes with latitude. The concept of observer's horizon only distracted me from thinking about the relative motions of the sun and earth. This cartoon about global twilight durations sorted it out for me:

http://www.mangobay.cc/users/moonfinder/sep-99.htm

and this one about seasonal twilight durations was also helpful:

http://www.mangobay.cc/users/moonfinder/aug-98.htm

but I don't know if it's appropriate to add these links to Wikipedia (I'm new here). The cartoons originally appeared in Sky & Telescope magazine.

--ELefty 19:13, 3 July 2007 (UTC)

[edit] Ecclesiastical uses of twilight

The article as it stands mentions twilight in the context of the day's fasting during Ramadan. My understanding (which I don't trust enough to add to the article; it contradicts the information in day, for one thing) is that in Jewish ecclesiastical practice, the end of one day/beginning of the next happens in evening twilight, when it is dark enough that one cannot distinguish a blue thread from a black thread when they are held in the hand at arm's length. Expand the "other uses" section, perhaps renaming it, to include these and related points? BSVulturis 19:45, 29 December 2006 (UTC)

[edit] twilight before dusk?

is twilight bfore dusk or is it the ther way around?--Hicups0002 08:19, 27 January 2007 (UTC)

Neither, evening twilight is dusk; morning twilight is dawn (in the broad sense, not to be confused with sunrise, which is the end of morning twilight). Refs: the USNO pages, etc. 193.122.47.170 18:58, 8 March 2007 (UTC)

[edit] Mention of burglary

The article mentions night-time burglary carrying a lesser penalty. Am I correct in thinking this is something that applies only in some US states and should be noted in this article? 82.151.234.75 12:14, 16 February 2007 (UTC)

This concept applies to Australian Law as well. As it is not univeral but is international I would prefer the wording "some juristictions". 202.134.253.55 13:25, 7 November 2007 (UTC)

[edit] Best time for photography

This article should contain what many photographic lessons say -- "Twilight" is the best time to take photos. Also, unrelated, but still a question -- should it be Nautical or Civil Twilight? —Preceding unsigned comment added by 125.17.142.146 (talk) 09:51, 25 October 2007 (UTC)

[edit] Sunsets?

Why is this page polluted with sunset photos? As the article points out, twilight refers to the light by which we can see once the sun has set (or before it rises). It needs illustrating with photographs showing this, not some incidental and gratuitous collection of pretty skies. Assuming no-one can provide a justification for them, I'll replace them with some more relevant images in the course of copyediting the page. --mikaultalk 14:14, 19 November 2007 (UTC)

I agree, especially with the silo photograph: twilight is when one can still see *without the aid of artificial light*, which is prominently shown in this photograph, despite the pretty evening star. Delete? --Stefankamph 08:48, 1 December 2007 (UTC)

Yes, I'd like to replace both those bottom two images, but at least the silos one shows a visible star (mentioned in adjacent text). The last photo needs to illustrate astronomical twilight (almost dark) so it's really there as a placeholder for now. I've uploaded one for civil twilight and hope to have replacements for these two soon. --mikaultalk 18:54, 1 December 2007 (UTC)
In response to the statement above, "twilight refers to the light", I would like to point out that the article indicates twilight is a period of time, not a kind of light. Therefore showing photos taken at this time that support related text in the article is not incidental. Maybe there were too many sunset pics, but consider this clarification when evaluating the reason some of the photos appeared on this page. - Shiftchange 21:57, 1 December 2007 (UTC)
I take your point, but technically, it's neither: it refers to the relative position of the sun. What the sky looks like is only borderline relevant, IMO. There's no picture of the sky at daylight, for example. Like daylight, it's more descriptive and easy to understand if it's partly defined by what it does, as much as what it is. It does kind of make the sky look pretty, but then that's (amply) dealt with at sunset. A good part of its definition is the practical relevance of twilight; basically, what you can and can't do at various stages just before daybreak or after sunset, which means including images of (or at) typical light levels.--mikaultalk 00:20, 2 December 2007 (UTC)

[edit] rejig

In fairness to those sunset images, I've removed the monument one for the same reason: we need to illustrate the light the sky gives off at these times, rather than the light remaining in the sky. A silhouette is obviously not giving that impression. The rest of the rejig was just to lay out the images better. The duration chart is awesome, btw :o) --mikaultalk 23:33, 28 November 2007 (UTC)

[edit] Brightness of Civil Twilight for "Normal Outdoor Activities"

I have always been perturbed by statements like "During this period [civil twilight] there is enough light from the Sun that artificial sources of light are not needed to carry on [normal] outdoor activities.". First of all, what are 'normal' outdoor activities? Second, at the risk of looking like original research, this needs to be questioned. If we consider the common sports listed at http://www.americanelectriclighting.com/sportslighting/LightLevels/Lux.asp to be 'normal' outdoor activities, the lux levels listed on that site occur naturally outdoors right around sunset or sunrise (under clear skies), rather than at the dark limit of civil twilight. (See http://www.burle.com/cgi-bin/byteserver.pl/pdf/Electro_Optics.pdf under Sources of Radiation in the table of Contents.) The illumination corresponding to the dark limit of civil twilight under clear skies is 3 lux, or roughly that of a candle at a distance of 58 centimeters (23 inches). This is considerably darker than the illumination standards used for many sports, reasonably representative of 'normal' outdoor activities. Something is wrong here. (Remember, dark limit of civil twilight = candlelight!)

I have changed the wording slightly in this statement in the article.

- User: Nightvid (unregistered)

[edit] Uht

I don't know where this could be put in, but the Anglo-Saxons had a concept of what they called 'uht,' which was the time just before twilight in the morning when supposedly the sky is blackest. 140.247.44.14 (talk) 07:41, 23 April 2008 (UTC)

[edit] Twilight versus daylight

The chart Image:TwilightLength.png seems to be confusing twilight with daylight. Twilight does not last for 12 or 14 hours a day in a typical region. - SimonP (talk) 13:51, 25 April 2008 (UTC)

No Simon the chart seems correct. Take a look at the discussion re: Civil, Nautical and Astronomical Twilight definitions below. - AdeBarkah (talk) 02:35, 5 May 2008 (UTC)


[edit] WRONG definitions of Civil, Nautical, and Astronomical Twilights!

It's very important to make a distinction between the casual concept of twilight and the technical terms Civil Twilight, Nautical Twilight and Astronomical Twilight which have counter-intuitive meanings!! In particular the main article got the definitions of Nautical Twilight and Astronomical Twilight completely wrong!

By definition, Civil Twilight begins in the morning when the sun is 6 degrees below the horizon, lasts through the day, and ends in the evening (when the sun is again 6 degrees below the horizon.) During this entire period, outdoor activities can generally be undertaken without the assistance of artificial lighting.

So there is really no "morning civil twilight" which ends at sunrise, or an "evening civil twilight" which starts at sunset. There is only one Civil Twilight: it begins in the morning and ends in the evening. For example, today in New York City Civil Twilight began at 5:20 AM and ended at 8:26 PM.

Similarly there is only one Nautical Twilight. Like Civil Twilight, it begins in the morning(!) (when the sun is 12 degrees below the horizon), lasts through the day, and ends in the evening (when the sun is again 12 degrees below the horizon.) Sailors generally cannot "take reliable star sights of well known stars" during Nautical Twilight as noted in the main article. They can do so either before or after Nautical Twilight, not during.

And you might have guessed it by now, there is only one Astronomical Twilight, which begins in the morning(!), lasts through the day, and ends in the evening. Astronomical Twilight begins and ends when the sun is 18 degrees below the horizon.

All of this is explained in detail at the US Navy page referenced by the main article: http://aa.usno.navy.mil/faq/docs/RST_defs.php.

- AdeBarkah (talk) 02:30, 5 May 2008 (UTC)

Okay, I don't know where you learned your twilight from but that's not how it is. If you look closely, it says for computational purposes, meaning that that's almost a spherical cow. Notice how every other twilight definition is ambiguous. Any other source should show morning or evening civil, naut etc. Sailors generally do take star sights during nautical twilight because if they did it brighter the bright stars couldn't be seen and if they did it darker the sky'd be too dim to stand out against the sea well and see the horizon's (to measure their altitude). Notice that what is said about stars at end of civil twilight, EOCT=BONT. Full Moons, or Scottish midsummer midnights are equivalent to nautical twilight. Cities are nautical twilight or greater forever. Sagittarian Milky Way (talk) 14:18, 7 May 2008 (UTC)
Actually AdeBarkah has succinctly explained the difference in terms, the image that raised the contention is accurate and the article needs to be clarify the terms more accurately. Civil, nautical and astronomical twilights all begin in the morning and end in the evening. If you run a twilight report in the program called Astronomy Lab 2, for example, it will confirms this. - Shiftchange (talk) 23:11, 7 May 2008 (UTC)
Hmm this is interesting and unexpected. I was looking for Chicago twilight times on the web and noticed this too. They begin in the morning and end in the evening. I find it strange that astronomical twilight starts in the morning but I guess it does. Eg. http://www.timeanddate.com/worldclock/city.html?n=64 for Chicago. I'm a pilot and we do say "morning civil twilight" but the FAA regs define the three twilights exactly the same as the Navy definitions AdeBarkah refers to (word per word.)
I would say that this is a technicality in the definitions. It is correct that civil twilight begins in the morning and ends in the evening according to the astronomical definitions. The same goes for nautical twilight and astronomical twilight. Thus, during the day - technically - it is civil, nautical and astronomical twilight at the same time. However, daylight takes precedence over civil twilight, civil twilight over nautical twilight etc. for all practical purposes. Therefore (in the morning) the astronomical twilight is "suspended" by the onset of nautical twilight, which in turns is "suspended" by the onset of civil twilight. I think it is better to stay with the definitions as they are and mention this technicality in a side note? 90.184.242.141 (talk) 17:04, 5 June 2008 (UTC)

[edit] Twilight Zone

Should there be a reference to the TV show The Twilight Zone on this page? The TV show takes its name from the natural phenomenon. Theneogon (talk) 02:18, 29 May 2008 (UTC)