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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)
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)
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)
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)
The graph currently accompanying this section does not show duration of twilight. It shows total duration of daylight (from dusk to dawn).
68.122.104.16 (
talk)
01:22, 25 October 2008 (UTC)
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)
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)
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 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)
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. -- mikaul talk 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)
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) -- mikaul talk 23:33, 28 November 2007 (UTC)
The twilight zone is one of the most amazing places. It is DARK and thats awesome! hehehehehehehehe —Preceding unsigned comment added by 134.197.171.254 ( talk) 20:26, 23 September 2008 (UTC)
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)
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)
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)
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)
Hmmm, the 9th edition of the OED gives twilight as the period after sunset, and dusk as the latter and darker part of this. I realise that the OED gives commonly accepted usage and not always the rigorous definitions by supposedly authoritative bodies, but, shouldn't this definition be mentioned?
68.228.208.191 (
talk)
01:19, 26 September 2008 (UTC)
Addendum to above comment............
Shouldn't the 'authorities' who define twilight as per the article be mentioned? Also, in an encyclopedic article, it might be helpful to state where they derive their authority from.
In the UK, twilight is generally accepted as the period after sunset; hence, such expressions as "twilight of the Gods", or "the twilight of one's life", both expressions indicative of the concept of "day's end". :)
68.228.208.191 ( talk) 01:51, 26 September 2008 (UTC)
I'm not a native english speaker, so I dont actually know the precise meaning of twilight, but there is some conflict between 2 articles:
Dusk states:
"Dusk refers to the period of time following sunset. Although commonly confused with twilight, dusk is the time frame that occurs either before or after a twilight..."
Twilight states:
"Twilight is the time before sunrise (dawn), and the time after sunset (dusk)..."
Which one is correct? Almighty11 ( talk) 20:33, 30 November 2008 (UTC)
The reversion swept away corrections to the text as well as the image placement.
The article says:
The link given, as well as other discussion on this talk page, says otherwise. Twilight includes all times "during which it is possible to conduct outdoor activities ...", including broad daylight. That is not the definition I am accustomed to, but it is the technical definition.
The edit summary in the reversion says "please place diagrams elsewhere." Such as ...? Could it not have been moved to that suggested location instead of reverted? - Wmc824 ( talk) 20:44, 31 December 2008 (UTC)
This article claims that in Oslo 59° 57’ (59.95°), Stockholm 59° 21’ (59.35°), Helsinki 60° 10’ (60.17°), Tallin 59° 26’ (59.43°)and Saint Petersburg 59° 56’ (59.93°); "civil twilight lasts allnight in midsummer". Furthermore, that in Hamburg 53° 35’ (53.58°), Gdansk 54° 22’ (54.37°) and Edmonton 53° 32’ (53.54°); "nautical twilight lasts allnight in midsummer". These are blatantly false. Received this in an e-mail from the U.S. Naval Observatory, "Nautical twilight begins and ends when the center of the sun is 12 degrees below the horizon. Therefore the most extreme latitude (north or south) that Nautical Twilight can last all night is 90 - 12 - obliquity of the ecliptic. The obliquity is now 23 degrees 26 minutes, which makes the most extreme latitude indeed 54 degrees 34 minutes" (54.56667°). Therefore, Astronomical Twilight is 90 degrees - 18 degrees = 72 degrees - 23 degrees 26 minutes = 48 degrees 34 minutes (48.56667°). Civil Twilight is 90 degrees - 6 degrees = 84 degrees - 23 degrees 26 minutes = 60 degrees 34 minutes (60.56667°). The websites below will confirm this, by imputing coordinates. Impute 60° 34’ (60.56667°) with a longitude and the correct time zone. You will see that Civil twilight does occur on the longest days. However, impute 60° 33’ (60.55°) and you will find that Civil twilight does not occur, even on the longest days. The same will occur with Nautical twilight, 54° 34’ (54.56667°) does occur, 54° 33’ (54.55°) does not occur. Astronomical twilight, 48° 34’ (48.56667°) does occur, 48° 33’ (48.55°) does not occur: HM Nautical Almanac Office, Websurf: http://websurf.nao.rl.ac.uk/ Geoscience Australia: http://www.ga.gov.au/geodesy/astro/sunrise.jsp Federal Aviation Administration, Sunrise/Sunset/Twilight/Calculator: http://akweathercams.faa.gov/srsscalc.php In June 2008, I received this e-mail from the U.S. Naval Observatory, "Further testing we have done seems to indicate that our online program may be missing some phenomena at this near-degenerate case; that is at the longitudes you tested, below N54 34 limit, the program should have found that there was a specific beginning and end to nautical twilight and not shown ////. We are investigating now to most simply modify the program to find these cases. The repair will take several weeks at best. Thanks for your diligence in testing our application and for your e-mail calling attention to the problem." However, I have just tested the coordinates, that I found were incorrect in June 2008. They were in the UK, Germany, Russia and Canada. All with exception of the Canadian coordinates, are still producing errors regarding twilight. The above latitudes for twilight are approximate. So, with the precise figure for the obliquity of the ecliptic; the precise latitudes could be obtained, for that date. They are in my opinion, very slightly below those I have shown. Sulasgeir ( talk) 23:29, 15 January 2009 (UTC)
I'm the unlisted editor who recently made changes.... [in deleting] ... obvious idiocy and irrelevance.
CheshiresMasquerade ( talk) 16:02, 7 January 2009 (UTC)
Since there are blatent errors, I have edited the "2 Length" part of this article. My reasons are above in 18, Twilight All Night: Astronomical, Nautical, Civil. Sulasgeir ( talk) 03:16, 16 January 2009 (UTC)
How about the South African band "Civil Twilight"? It doesn't seem that there's an entry about the band in wikipedia, and it seems a bit unrelated to put it in the disambiguation page of "Twilight". How about adding a new disambig page for "CIvil Twilight" and to reconsider redirecting all links of "Civil Twilight" to "Twilight#Civil Twilight". —Preceding unsigned comment added by 142.151.157.70 ( talk) 22:26, 28 February 2009 (UTC)
This is because at low latitudes the sun's apparent movement is perpendicular to the observer's horizon, in addition to the fact that the rotational speed of a specific location is highest at the Equator and slower as latitude increases. This doesn't make sense / isn't clear to me ... the rotational speed of the earth should be the same everywhere. Unless it's referring to rotational speed on an axis perpendicular to the sun? Anyway, it would be cool if someone were to reword. Gerardw ( talk) 21:38, 12 May 2009 (UTC)
In response to Gerardw. http://www.ncgia.ucsb.edu/education/curricula/giscc/units/u014/tables/table02.html The Earth's Equatorial circumference is 24901.5 miles therefore 1 degree longitude equates to 69.17 miles.This 69.17 miles also represents the speed at which the Earth turns at the Equator every 4 minutes and makes an entire 24901.5 mile rotation in 24 hours.At 60 degree latitude,the distance for 1 degree and speed for 4 minutes is 34.67 miles.It follows that the quicker speed at the Equator gives the effect of a rapid transition from daylight to darkness while at 60 degrees latitude,a person experiences a slower transition from daylight to darkness.
The huge problem is that the widely accepted value for the Earth's 360 degree rotation is not 24 hours but a false late 17th century contrivance otherwise known as 'sidereal time'.That value cannot express the rotational speeds needed to explain the twilight effect as it contains no information about planetary shape or rotational characteristics.If you try to use the 23 hour 56 minute 04 second value along with planetary geometry to explain the difference between Equatorial and more polar latitudes in terms of twilight,you will quickly develop a distinct antipathy towards 'sidereal time' and the reasoning behind it. Oriel36 ( talk) 22:24, 12 July 2009 (UTC)
Latitudinal speeds are crucial to understanding why there is a rapid transition to darkness at the Equator and less so towards the geographical poles as rotational speeds diminish with latitude. Removing daily rotation and subsequently, different latitudinal speeds as the main cause of latitudinal variations in twilight leaves nothing but the useless explanation based on the motion of the Sun as a cause.Before you remove planetary dynamics from the explanation and focus on the motion of the Sun,I strongly suggest you come to terms with astronomical scale - http://images.funadvice.com/photo/image/old/39032/Sun__Earth_size_comparison_labeled.jpg Restore planetary dynamics to the explanation and clarity returns to the twilight explanation while omiting dynamics leaves nothing but a geostatic mess based on the motions of the Sun. Oriel36 ( talk) 10:50, 10 August 2009 (UTC)
Why are you begging an 'If' question from me ?, the Equatorial speed of the Earth is 1669.8 km per hour and 837 km per hour at 60 degree latitude causing the twilight effect to be longer as the rotational speed diminishes towards the geographical poles.If you can't comprehend that as a location rotates into the orbital shadow at a slower speed you get longer twilights you belong nowhere near this topic. Oriel36 ( talk) 17:06, 11 August 2009 (UTC)
The imperative I have to give to you is to discover that the Earth is round and rotating and the values for rotation at different latitudes are known and have definite effects such as the faster the rotation the quicker the transition from daylight to darkness,anyone who can't respond to this cause and effect with the appropriate affirmation has no business near astronomical timekeeping,planetary dynamics and the effects of these daily rotational and orbital dynamics. Oriel36 ( talk) 17:16, 12 August 2009 (UTC)
Daily rotation causes the day and night cycle,have you got that straight?,now,the next thing you can say is because the Earth is a rotating sphere, the maximum rotational speed is at the Equator and diminishes towards the geographical poles.Here are those values representing 4 minutes/1 degree of rotation- http://www.ncgia.ucsb.edu/education/curricula/giscc/units/u014/tables/table02.html .Now,common sense,and it is common sense,determines that at any given time,a location at the Equator is transiting through the boundary between solar radiation (daylight) and the orbital shadow (darkness) at 1669.8 km per hour while a location at 60 degrees Latitude either side of the Equator is transiting through the same boundary at 837 km per hour irrespective of seasonal differences.The effect at the Equator compared to that at 60 degree latitudes is that twilight is longer compared to the rapid transition at the Equator at all times.Of course,the same people who cannot describe the twilight effect properly based on rotational dynamics refuse to accept the rotational speeds in that table above and this means that you have a problem with the basic day and night cycle let alone latitudinal twilight comparisons and their causes.Let me see what value you give for daily rotation per hour at the Equator and 60 degrees and then we can talk. Oriel36 ( talk) 09:16, 13 August 2009 (UTC)
It is not at all difficult to understand the cause (latitudinal rotation speeds) and effect (twilight variations) and the dynamical explanation should present no comprehension problem for any student or reasonable person.The previous explanation is good enough for anyone and if you cannot understand the link between rotational dynamics and why darkness descends quickly at the Equator and slower towards either poles,irrespective of the seasons,I have no intention of listening to any other cause than rotational dynamics for the simple reason is that there is no other explanation. Oriel36 ( talk) 21:14, 13 August 2009 (UTC)
There is no superiority,the cause and effect is so simple to grasp ,latitudinal variations in rotational speed correlate with longer twilights with the most rapid transition to darkness existing at the Equator that any other imagined cause would be beneath me to consider.The latitudinal twilight variations are an intrinsic part of daily rotation and after the cause of the daylight/darkness cycle due to daily rotation ,the next insight is straightforward enough as the Earth is a rotating sphere with rotational characteristics which see latitudes towards the geographical axis produce longer and longer twilights as part of the daily cycle.If you pair cannot understand it this way,how would you expect the wider population to understand it. Oriel36 ( talk) 13:07, 14 August 2009 (UTC)
ISTM that the section on length is beginning to read more like an almanac than an encyclopedia. All the details about when twilight happens, how long it lasts in a multitude of particular spots, etc., seems a bit overmuch to me. - Ac44ck ( talk) 03:44, 9 July 2009 (UTC)
Material about the change in obliquity over centuries belongs in another article. — Tamfang ( talk) 22:49, 17 July 2009 (UTC)
I reverted the restoration of info about latitudes. Note the text at the bottom of an edit page: "Content that violates any copyrights will be deleted. Encyclopedic content must be verifiable".
- Ac44ck ( talk) 00:34, 21 July 2009 (UTC)
Okay, let's discuss it. What's the spacing issue here? To me it looks about the same either way; is there a problem in narrow windows or something? — Tamfang ( talk) 03:05, 21 August 2009 (UTC)
I believe that the point of taking note of twilight lasting "all night" is that it lasts for at least 24 hours; or one rotation; or some such.
While it may be incorrect to say "twilight lasts for exactly 24 hours" for days on end, the intro which said "These are the largest cities, of their respective countries, where 24-hour twilight can occur" may have been accurate.
Dusk and dawn are not defined verbally in this twilight article. The article on dusk isn't very precise; but the article on dawn is: "civil dawn" is different from "nautical dawn". Can there be a transition from dusk to dawn if it doesn't stop being twilight? - Ac44ck ( talk) 01:53, 9 September 2009 (UTC)
This is part of the description given for the summary for the image in the article.
"Approximate length of daylight, in hours, as a function of latitude and time of year. Here, the length of daylight is defined as the period from the beginning of civil twilight in the morning to the end of civil twilight in the evening. Morning civil twilight begins before sunrise when the sun is geometrically 6 degrees below the horizon and ends when the sun rises; evening civil twilight lasts from sunset until the sun is geometrically 6 degrees below the horizon. Civil twilight is roughly the period before sunrise and after sunset during which, under clear skies, outdoor activities can be carried out without artificial light."
It clearly states the definition of civil twilight and therefore the continuous civil twilight in the picture refers to technical twilight. The text in the picture has been badly worded, it should say continuous daylight. The sun being both above twilight limit and above the horizon for an entire month can be interpreted by simply having the horizon be the twilight limit, therefore above twilight limit and above the horizon mean the same thing. Better still would be to call 6 degrees below the horizon the lower twilight limit so that the horizon can be called the upper twilight limit. Hope this helps. Set Sail For The Seven Seas 331° 29' 0" NET 22:05, 16 September 2009 (UTC)
I think that that the diagram is correct, but that the technical twilight part has been put there to help understand it in comparison to twilight. Strictly speaking, technical twilight should solely be used in computation where it simplifies the creation of programs to calculate twilight times, but the output should display twilight with daytime and not technical twilight. Also, it shouldn't be too difficult to calculate the length of twilight once you have the beginning and the end of that particular twilight. The various links here link to online calculators for twilight. Also, I think we can agree now that the twilight article is accurate and that the terminology is correct. Hope this helps. Set Sail For The Seven Seas 332° 54' 0" NET 22:11, 18 September 2009 (UTC)
You're right, this is getting a little muddled up, so I'll simply state the points I'm making here:
1. Twilight is limited to before sunrise and after sunset.
2. Daytime is the time between sunrise and sunset.
3. Technical Twilight is Twilight plus Daytime.
4. Twilight and Technical Twilight are not the same and this needs to be made clear to the readers.
5. During astronomical twilight "all night", astronomical twilight lasts from nautical dusk to nautical dawn.
6. During nautical twilight "all night", nautical twilight lasts from civil dusk to civil dawn.
7. During civil twilight "all night", civil twilight lasts from sunset to sunrise.
OK, ignore this bit, it's irrelevant to my point and not a good arguement.
The situation here is that there are two terms, twilight and technical twilight, two definitions, without daytime and with daytime, and a huge clash. By stating that twilight is without daytime and technical twilight is with daytime, which is the definition given in the picture, it makes understanding both twilight and technical twilight so much easier.
I get the idea that you are inclined towards wiping out all traces of technical twilight and sticking to twilight. I would agree with it, but my only concern with this is that some readers will still think of twilight being with daytime and then we have this scenario all over again and then we would be going round in circles and not getting anywhere. If you can sort out this concern then I will agree and remove the technical twilight arrow from the picture in the definitions section.
The reason I mentioned this is because at the point that the morning and evening twilights merge into one, morning twilight is suddenly included in an instant. My point here is, Why the sudden inclusion of morning twilight? It brings an abrupt and misleading jolt to the length of twilight. I completely agree that the in the strict boundaries of the definitions, the passing between daytime, night and the various twilights are completely abrupt, but the length of twilight will never increase or decrease abruptly. Google Earth's sun feature shows this very well.
We can agree that the occurring of the various twilights passing through local midnight is based on the lowest point of the sun or the lower culmination of the sun. This lower culmination will gradually sink upon moving away from the summer solstice and gradually rise upon moving towards from the summer solstice, with the lower culmination of the sun being at its highest at the summer solstice. Google Earth's sun feature will confirm this.
If the latitude chosen is high enough, then upon approaching the summer solstice, the night (sun 18° below the horizon) will slowly decrease in length and reach zero as the lower culmination of the sun rises to and reaches 18° below the horizon then astronomical twilight "all night" occurs.
Astronomical twilight will then slowly decrease in length and reach zero as the lower culmination of the sun rises to and reaches 12° below the horizon, then nautical twilight "all night" occurs.
Nautical twilight will then slowly decrease in length and reach zero as the lower culmination of the sun rises to and reaches 6° below the horizon, then civil twilight "all night" occurs.
Civil twilight will then slowly decrease in length and reach zero as the lower culmination of the sun rises to and reaches the horizon, then the midnight sun occurs.
Each twilight will only start to decrease once the lower culmination of the sun has reached its lower limit. The reverse happens upon leaving the summer solstice.
The only problem that occurs to me here is that the text is wrong, which is a minor problem. Suppose the text in the graph said continuous daylight instead of continuous civil twilight and no daylight instead of no civil twilight. Would it then be worthy of remaining in the article? I would think so because the graph points out an interesting phenomena resulting from civil twilight, which is that the latitudes 60° 33’ 43” and 72° 33’ 43” can experience 24 hour daylight or continuous technical civil twilight at the summer solstice, which is equivalent to the presence of sunlight all day, and not experience 24 hour darkness or civil polar night at the winter solstice.
I think I've explained everything as clearly as possible. Hope this helps. Set Sail For The Seven Seas 340° 18' 0" NET 22:41, 20 September 2009 (UTC)
I think of technical twilight as just a computerised version of the term twilight, a term used to help disambiguate between the two. There wouldn't be any references to it as it is pretty much a dummy term; that said, it does help with the understanding of twilight quite significantly.
I was thinking that the confusion was started due badly written external sources, hence the reasoning of keeping technical twilight, since AdeBarkah quoted external sources when the arguement was made. So it stands to reason that another reader could easily follow in AdeBarkah's footsteps saying that the definitions are wrong. Now, I was thinking that we could explain to this reader that their definitions were actually technical twilight, tell them that this is a computerised definition and then explain to them the actual definition of twilight. On the other hand, AdeBarkah misread the source article, so it stands to reason that it could be an error on the reader's behalf. If the confusion is indeed solely of Wikipedia's making, then I will agree with the wiping out of technical twilight, but there should be a mention of disambiguation. OK, I agree that an entire section on technical twilight is complete overkill, so I'm thinking a small sentence at the top along the lines of, "not to be confused with technical twilight, which is ..." or something similar, that way it makes the definition of twilight completely crystal clear with no disambiguation.
I think I can see what is going on here. You're referring to the extremely high latitudes, specifically the poles, while I'm thinking of latitudes around those mentioned in the length section. At the poles, I will completely agree, it is true that there is this extremity at the various transition points, but I believe the only living at and around the vicinity of the poles are those at the Amundsen-Scott South Pole Station, and I doubt they would be reading this Wikipedia article! Mind you, it is a point of interest and so should be shown. Another thing, the scenario where the morning and evening twilights merge into one doesn't occur at the poles and so is irrelevant for that latitude.
This is what it should have been considering the latitudes I was referring to. Of course, at the higher latitudes where polar night exists, then there will be no twilight, then a quick but smooth increase, then a slow decrease, then a slow increase, then a quick but smooth decrease until there is no twilight again. As the latitude increases, the changes in twilight duration will get faster and faster until they become instantaneous at the poles.
This bit explains what happens at the solstices as the latitude varies.
I think the actual point here is not the inclusion of the graph, but about the inclusion of the interesting phenomena resulting from civil twilight that is shown in the graph. So maybe if a section on this phenomena is added to the article, the graph can be added there; if not though, the article should still mention the phenomena, as it is solely based on twilight. Hope this helps. Set Sail For The Seven Seas 264° 4' 15" NET 17:36, 21 September 2009 (UTC)
Type of twilight Upper twilight limit Lower twilight limit
Civil twilight < -0°50' (sunrise/sunset) <= -6°
Nautical twilight < -6 <= -12
Astronomical twilight < -12 <= -18
Has anyone considered that "X technical twilight, xx.x hrs" is shorthand for "X twilight or worse for xx.x hours"? A length of evening twilight graph should max out at 12 hours (with a note to explain this) to keep the (nonexistant?) morning graph a mirror image of the evening. You can't start assigning all eternal twilight hours to evening just cause you want it to show 24, otherwise you can get the ridiculous notion that evening technical twilight occurs simulaneously with sunrise. Now what should be the cutoffs, mean local midnight and noon or actual? Sagittarian Milky Way ( talk) 07:29, 22 September 2009 (UTC)
I agree with the limits for the various forms of twilight, though I'd probably think of it more like this.
Definition | Position of sun |
Night | more than 18° |
Astronomical twilight | 12°<AT<18° |
Nautical twilight | 6°<NT<12° |
Civil twilight | -0°50'<CT<6° |
Day | sun above the horizon |
Also, the boundaries are marked by the various dawns and dusks or sunrise and sunset.
But for people without an intuitive knowledge of twilight this would be very misleading. It just needs a retitiling. "Hours of usable natural light". This would be useful in gauging how bright a night is at summer. Even so, reversing the hours might be slightly more useful for showing number of observable hours -- it would tell me that at Anchorage where many people live (for example), the sky would be bright enough to play baseball for pretty much the entire night, which is, needless to say, annoying. Sagittarian Milky Way ( talk) 01:57, 24 September 2009 (UTC)
I think at this point I can agree with removing technical twilight, as things should indeed be a simple as possible, but not simpler, otherwise we end up with a spherical cow!
One other thing about the graph, it should show the total amount of twilight per day, that's why morning twilight and evening twilight should be added up, as has been done with the existing graph. Also, I think Sagittarian Milky Way has a good point about this. Both twilights should be included otherwise it is not the total amount of twilight. Hope this helps. Set Sail For The Seven Seas 243° 43' 15" NET 16:14, 22 September 2009 (UTC)
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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)
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)
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)
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)
The graph currently accompanying this section does not show duration of twilight. It shows total duration of daylight (from dusk to dawn).
68.122.104.16 (
talk)
01:22, 25 October 2008 (UTC)
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)
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)
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 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)
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. -- mikaul talk 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)
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) -- mikaul talk 23:33, 28 November 2007 (UTC)
The twilight zone is one of the most amazing places. It is DARK and thats awesome! hehehehehehehehe —Preceding unsigned comment added by 134.197.171.254 ( talk) 20:26, 23 September 2008 (UTC)
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)
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)
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)
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)
Hmmm, the 9th edition of the OED gives twilight as the period after sunset, and dusk as the latter and darker part of this. I realise that the OED gives commonly accepted usage and not always the rigorous definitions by supposedly authoritative bodies, but, shouldn't this definition be mentioned?
68.228.208.191 (
talk)
01:19, 26 September 2008 (UTC)
Addendum to above comment............
Shouldn't the 'authorities' who define twilight as per the article be mentioned? Also, in an encyclopedic article, it might be helpful to state where they derive their authority from.
In the UK, twilight is generally accepted as the period after sunset; hence, such expressions as "twilight of the Gods", or "the twilight of one's life", both expressions indicative of the concept of "day's end". :)
68.228.208.191 ( talk) 01:51, 26 September 2008 (UTC)
I'm not a native english speaker, so I dont actually know the precise meaning of twilight, but there is some conflict between 2 articles:
Dusk states:
"Dusk refers to the period of time following sunset. Although commonly confused with twilight, dusk is the time frame that occurs either before or after a twilight..."
Twilight states:
"Twilight is the time before sunrise (dawn), and the time after sunset (dusk)..."
Which one is correct? Almighty11 ( talk) 20:33, 30 November 2008 (UTC)
The reversion swept away corrections to the text as well as the image placement.
The article says:
The link given, as well as other discussion on this talk page, says otherwise. Twilight includes all times "during which it is possible to conduct outdoor activities ...", including broad daylight. That is not the definition I am accustomed to, but it is the technical definition.
The edit summary in the reversion says "please place diagrams elsewhere." Such as ...? Could it not have been moved to that suggested location instead of reverted? - Wmc824 ( talk) 20:44, 31 December 2008 (UTC)
This article claims that in Oslo 59° 57’ (59.95°), Stockholm 59° 21’ (59.35°), Helsinki 60° 10’ (60.17°), Tallin 59° 26’ (59.43°)and Saint Petersburg 59° 56’ (59.93°); "civil twilight lasts allnight in midsummer". Furthermore, that in Hamburg 53° 35’ (53.58°), Gdansk 54° 22’ (54.37°) and Edmonton 53° 32’ (53.54°); "nautical twilight lasts allnight in midsummer". These are blatantly false. Received this in an e-mail from the U.S. Naval Observatory, "Nautical twilight begins and ends when the center of the sun is 12 degrees below the horizon. Therefore the most extreme latitude (north or south) that Nautical Twilight can last all night is 90 - 12 - obliquity of the ecliptic. The obliquity is now 23 degrees 26 minutes, which makes the most extreme latitude indeed 54 degrees 34 minutes" (54.56667°). Therefore, Astronomical Twilight is 90 degrees - 18 degrees = 72 degrees - 23 degrees 26 minutes = 48 degrees 34 minutes (48.56667°). Civil Twilight is 90 degrees - 6 degrees = 84 degrees - 23 degrees 26 minutes = 60 degrees 34 minutes (60.56667°). The websites below will confirm this, by imputing coordinates. Impute 60° 34’ (60.56667°) with a longitude and the correct time zone. You will see that Civil twilight does occur on the longest days. However, impute 60° 33’ (60.55°) and you will find that Civil twilight does not occur, even on the longest days. The same will occur with Nautical twilight, 54° 34’ (54.56667°) does occur, 54° 33’ (54.55°) does not occur. Astronomical twilight, 48° 34’ (48.56667°) does occur, 48° 33’ (48.55°) does not occur: HM Nautical Almanac Office, Websurf: http://websurf.nao.rl.ac.uk/ Geoscience Australia: http://www.ga.gov.au/geodesy/astro/sunrise.jsp Federal Aviation Administration, Sunrise/Sunset/Twilight/Calculator: http://akweathercams.faa.gov/srsscalc.php In June 2008, I received this e-mail from the U.S. Naval Observatory, "Further testing we have done seems to indicate that our online program may be missing some phenomena at this near-degenerate case; that is at the longitudes you tested, below N54 34 limit, the program should have found that there was a specific beginning and end to nautical twilight and not shown ////. We are investigating now to most simply modify the program to find these cases. The repair will take several weeks at best. Thanks for your diligence in testing our application and for your e-mail calling attention to the problem." However, I have just tested the coordinates, that I found were incorrect in June 2008. They were in the UK, Germany, Russia and Canada. All with exception of the Canadian coordinates, are still producing errors regarding twilight. The above latitudes for twilight are approximate. So, with the precise figure for the obliquity of the ecliptic; the precise latitudes could be obtained, for that date. They are in my opinion, very slightly below those I have shown. Sulasgeir ( talk) 23:29, 15 January 2009 (UTC)
I'm the unlisted editor who recently made changes.... [in deleting] ... obvious idiocy and irrelevance.
CheshiresMasquerade ( talk) 16:02, 7 January 2009 (UTC)
Since there are blatent errors, I have edited the "2 Length" part of this article. My reasons are above in 18, Twilight All Night: Astronomical, Nautical, Civil. Sulasgeir ( talk) 03:16, 16 January 2009 (UTC)
How about the South African band "Civil Twilight"? It doesn't seem that there's an entry about the band in wikipedia, and it seems a bit unrelated to put it in the disambiguation page of "Twilight". How about adding a new disambig page for "CIvil Twilight" and to reconsider redirecting all links of "Civil Twilight" to "Twilight#Civil Twilight". —Preceding unsigned comment added by 142.151.157.70 ( talk) 22:26, 28 February 2009 (UTC)
This is because at low latitudes the sun's apparent movement is perpendicular to the observer's horizon, in addition to the fact that the rotational speed of a specific location is highest at the Equator and slower as latitude increases. This doesn't make sense / isn't clear to me ... the rotational speed of the earth should be the same everywhere. Unless it's referring to rotational speed on an axis perpendicular to the sun? Anyway, it would be cool if someone were to reword. Gerardw ( talk) 21:38, 12 May 2009 (UTC)
In response to Gerardw. http://www.ncgia.ucsb.edu/education/curricula/giscc/units/u014/tables/table02.html The Earth's Equatorial circumference is 24901.5 miles therefore 1 degree longitude equates to 69.17 miles.This 69.17 miles also represents the speed at which the Earth turns at the Equator every 4 minutes and makes an entire 24901.5 mile rotation in 24 hours.At 60 degree latitude,the distance for 1 degree and speed for 4 minutes is 34.67 miles.It follows that the quicker speed at the Equator gives the effect of a rapid transition from daylight to darkness while at 60 degrees latitude,a person experiences a slower transition from daylight to darkness.
The huge problem is that the widely accepted value for the Earth's 360 degree rotation is not 24 hours but a false late 17th century contrivance otherwise known as 'sidereal time'.That value cannot express the rotational speeds needed to explain the twilight effect as it contains no information about planetary shape or rotational characteristics.If you try to use the 23 hour 56 minute 04 second value along with planetary geometry to explain the difference between Equatorial and more polar latitudes in terms of twilight,you will quickly develop a distinct antipathy towards 'sidereal time' and the reasoning behind it. Oriel36 ( talk) 22:24, 12 July 2009 (UTC)
Latitudinal speeds are crucial to understanding why there is a rapid transition to darkness at the Equator and less so towards the geographical poles as rotational speeds diminish with latitude. Removing daily rotation and subsequently, different latitudinal speeds as the main cause of latitudinal variations in twilight leaves nothing but the useless explanation based on the motion of the Sun as a cause.Before you remove planetary dynamics from the explanation and focus on the motion of the Sun,I strongly suggest you come to terms with astronomical scale - http://images.funadvice.com/photo/image/old/39032/Sun__Earth_size_comparison_labeled.jpg Restore planetary dynamics to the explanation and clarity returns to the twilight explanation while omiting dynamics leaves nothing but a geostatic mess based on the motions of the Sun. Oriel36 ( talk) 10:50, 10 August 2009 (UTC)
Why are you begging an 'If' question from me ?, the Equatorial speed of the Earth is 1669.8 km per hour and 837 km per hour at 60 degree latitude causing the twilight effect to be longer as the rotational speed diminishes towards the geographical poles.If you can't comprehend that as a location rotates into the orbital shadow at a slower speed you get longer twilights you belong nowhere near this topic. Oriel36 ( talk) 17:06, 11 August 2009 (UTC)
The imperative I have to give to you is to discover that the Earth is round and rotating and the values for rotation at different latitudes are known and have definite effects such as the faster the rotation the quicker the transition from daylight to darkness,anyone who can't respond to this cause and effect with the appropriate affirmation has no business near astronomical timekeeping,planetary dynamics and the effects of these daily rotational and orbital dynamics. Oriel36 ( talk) 17:16, 12 August 2009 (UTC)
Daily rotation causes the day and night cycle,have you got that straight?,now,the next thing you can say is because the Earth is a rotating sphere, the maximum rotational speed is at the Equator and diminishes towards the geographical poles.Here are those values representing 4 minutes/1 degree of rotation- http://www.ncgia.ucsb.edu/education/curricula/giscc/units/u014/tables/table02.html .Now,common sense,and it is common sense,determines that at any given time,a location at the Equator is transiting through the boundary between solar radiation (daylight) and the orbital shadow (darkness) at 1669.8 km per hour while a location at 60 degrees Latitude either side of the Equator is transiting through the same boundary at 837 km per hour irrespective of seasonal differences.The effect at the Equator compared to that at 60 degree latitudes is that twilight is longer compared to the rapid transition at the Equator at all times.Of course,the same people who cannot describe the twilight effect properly based on rotational dynamics refuse to accept the rotational speeds in that table above and this means that you have a problem with the basic day and night cycle let alone latitudinal twilight comparisons and their causes.Let me see what value you give for daily rotation per hour at the Equator and 60 degrees and then we can talk. Oriel36 ( talk) 09:16, 13 August 2009 (UTC)
It is not at all difficult to understand the cause (latitudinal rotation speeds) and effect (twilight variations) and the dynamical explanation should present no comprehension problem for any student or reasonable person.The previous explanation is good enough for anyone and if you cannot understand the link between rotational dynamics and why darkness descends quickly at the Equator and slower towards either poles,irrespective of the seasons,I have no intention of listening to any other cause than rotational dynamics for the simple reason is that there is no other explanation. Oriel36 ( talk) 21:14, 13 August 2009 (UTC)
There is no superiority,the cause and effect is so simple to grasp ,latitudinal variations in rotational speed correlate with longer twilights with the most rapid transition to darkness existing at the Equator that any other imagined cause would be beneath me to consider.The latitudinal twilight variations are an intrinsic part of daily rotation and after the cause of the daylight/darkness cycle due to daily rotation ,the next insight is straightforward enough as the Earth is a rotating sphere with rotational characteristics which see latitudes towards the geographical axis produce longer and longer twilights as part of the daily cycle.If you pair cannot understand it this way,how would you expect the wider population to understand it. Oriel36 ( talk) 13:07, 14 August 2009 (UTC)
ISTM that the section on length is beginning to read more like an almanac than an encyclopedia. All the details about when twilight happens, how long it lasts in a multitude of particular spots, etc., seems a bit overmuch to me. - Ac44ck ( talk) 03:44, 9 July 2009 (UTC)
Material about the change in obliquity over centuries belongs in another article. — Tamfang ( talk) 22:49, 17 July 2009 (UTC)
I reverted the restoration of info about latitudes. Note the text at the bottom of an edit page: "Content that violates any copyrights will be deleted. Encyclopedic content must be verifiable".
- Ac44ck ( talk) 00:34, 21 July 2009 (UTC)
Okay, let's discuss it. What's the spacing issue here? To me it looks about the same either way; is there a problem in narrow windows or something? — Tamfang ( talk) 03:05, 21 August 2009 (UTC)
I believe that the point of taking note of twilight lasting "all night" is that it lasts for at least 24 hours; or one rotation; or some such.
While it may be incorrect to say "twilight lasts for exactly 24 hours" for days on end, the intro which said "These are the largest cities, of their respective countries, where 24-hour twilight can occur" may have been accurate.
Dusk and dawn are not defined verbally in this twilight article. The article on dusk isn't very precise; but the article on dawn is: "civil dawn" is different from "nautical dawn". Can there be a transition from dusk to dawn if it doesn't stop being twilight? - Ac44ck ( talk) 01:53, 9 September 2009 (UTC)
This is part of the description given for the summary for the image in the article.
"Approximate length of daylight, in hours, as a function of latitude and time of year. Here, the length of daylight is defined as the period from the beginning of civil twilight in the morning to the end of civil twilight in the evening. Morning civil twilight begins before sunrise when the sun is geometrically 6 degrees below the horizon and ends when the sun rises; evening civil twilight lasts from sunset until the sun is geometrically 6 degrees below the horizon. Civil twilight is roughly the period before sunrise and after sunset during which, under clear skies, outdoor activities can be carried out without artificial light."
It clearly states the definition of civil twilight and therefore the continuous civil twilight in the picture refers to technical twilight. The text in the picture has been badly worded, it should say continuous daylight. The sun being both above twilight limit and above the horizon for an entire month can be interpreted by simply having the horizon be the twilight limit, therefore above twilight limit and above the horizon mean the same thing. Better still would be to call 6 degrees below the horizon the lower twilight limit so that the horizon can be called the upper twilight limit. Hope this helps. Set Sail For The Seven Seas 331° 29' 0" NET 22:05, 16 September 2009 (UTC)
I think that that the diagram is correct, but that the technical twilight part has been put there to help understand it in comparison to twilight. Strictly speaking, technical twilight should solely be used in computation where it simplifies the creation of programs to calculate twilight times, but the output should display twilight with daytime and not technical twilight. Also, it shouldn't be too difficult to calculate the length of twilight once you have the beginning and the end of that particular twilight. The various links here link to online calculators for twilight. Also, I think we can agree now that the twilight article is accurate and that the terminology is correct. Hope this helps. Set Sail For The Seven Seas 332° 54' 0" NET 22:11, 18 September 2009 (UTC)
You're right, this is getting a little muddled up, so I'll simply state the points I'm making here:
1. Twilight is limited to before sunrise and after sunset.
2. Daytime is the time between sunrise and sunset.
3. Technical Twilight is Twilight plus Daytime.
4. Twilight and Technical Twilight are not the same and this needs to be made clear to the readers.
5. During astronomical twilight "all night", astronomical twilight lasts from nautical dusk to nautical dawn.
6. During nautical twilight "all night", nautical twilight lasts from civil dusk to civil dawn.
7. During civil twilight "all night", civil twilight lasts from sunset to sunrise.
OK, ignore this bit, it's irrelevant to my point and not a good arguement.
The situation here is that there are two terms, twilight and technical twilight, two definitions, without daytime and with daytime, and a huge clash. By stating that twilight is without daytime and technical twilight is with daytime, which is the definition given in the picture, it makes understanding both twilight and technical twilight so much easier.
I get the idea that you are inclined towards wiping out all traces of technical twilight and sticking to twilight. I would agree with it, but my only concern with this is that some readers will still think of twilight being with daytime and then we have this scenario all over again and then we would be going round in circles and not getting anywhere. If you can sort out this concern then I will agree and remove the technical twilight arrow from the picture in the definitions section.
The reason I mentioned this is because at the point that the morning and evening twilights merge into one, morning twilight is suddenly included in an instant. My point here is, Why the sudden inclusion of morning twilight? It brings an abrupt and misleading jolt to the length of twilight. I completely agree that the in the strict boundaries of the definitions, the passing between daytime, night and the various twilights are completely abrupt, but the length of twilight will never increase or decrease abruptly. Google Earth's sun feature shows this very well.
We can agree that the occurring of the various twilights passing through local midnight is based on the lowest point of the sun or the lower culmination of the sun. This lower culmination will gradually sink upon moving away from the summer solstice and gradually rise upon moving towards from the summer solstice, with the lower culmination of the sun being at its highest at the summer solstice. Google Earth's sun feature will confirm this.
If the latitude chosen is high enough, then upon approaching the summer solstice, the night (sun 18° below the horizon) will slowly decrease in length and reach zero as the lower culmination of the sun rises to and reaches 18° below the horizon then astronomical twilight "all night" occurs.
Astronomical twilight will then slowly decrease in length and reach zero as the lower culmination of the sun rises to and reaches 12° below the horizon, then nautical twilight "all night" occurs.
Nautical twilight will then slowly decrease in length and reach zero as the lower culmination of the sun rises to and reaches 6° below the horizon, then civil twilight "all night" occurs.
Civil twilight will then slowly decrease in length and reach zero as the lower culmination of the sun rises to and reaches the horizon, then the midnight sun occurs.
Each twilight will only start to decrease once the lower culmination of the sun has reached its lower limit. The reverse happens upon leaving the summer solstice.
The only problem that occurs to me here is that the text is wrong, which is a minor problem. Suppose the text in the graph said continuous daylight instead of continuous civil twilight and no daylight instead of no civil twilight. Would it then be worthy of remaining in the article? I would think so because the graph points out an interesting phenomena resulting from civil twilight, which is that the latitudes 60° 33’ 43” and 72° 33’ 43” can experience 24 hour daylight or continuous technical civil twilight at the summer solstice, which is equivalent to the presence of sunlight all day, and not experience 24 hour darkness or civil polar night at the winter solstice.
I think I've explained everything as clearly as possible. Hope this helps. Set Sail For The Seven Seas 340° 18' 0" NET 22:41, 20 September 2009 (UTC)
I think of technical twilight as just a computerised version of the term twilight, a term used to help disambiguate between the two. There wouldn't be any references to it as it is pretty much a dummy term; that said, it does help with the understanding of twilight quite significantly.
I was thinking that the confusion was started due badly written external sources, hence the reasoning of keeping technical twilight, since AdeBarkah quoted external sources when the arguement was made. So it stands to reason that another reader could easily follow in AdeBarkah's footsteps saying that the definitions are wrong. Now, I was thinking that we could explain to this reader that their definitions were actually technical twilight, tell them that this is a computerised definition and then explain to them the actual definition of twilight. On the other hand, AdeBarkah misread the source article, so it stands to reason that it could be an error on the reader's behalf. If the confusion is indeed solely of Wikipedia's making, then I will agree with the wiping out of technical twilight, but there should be a mention of disambiguation. OK, I agree that an entire section on technical twilight is complete overkill, so I'm thinking a small sentence at the top along the lines of, "not to be confused with technical twilight, which is ..." or something similar, that way it makes the definition of twilight completely crystal clear with no disambiguation.
I think I can see what is going on here. You're referring to the extremely high latitudes, specifically the poles, while I'm thinking of latitudes around those mentioned in the length section. At the poles, I will completely agree, it is true that there is this extremity at the various transition points, but I believe the only living at and around the vicinity of the poles are those at the Amundsen-Scott South Pole Station, and I doubt they would be reading this Wikipedia article! Mind you, it is a point of interest and so should be shown. Another thing, the scenario where the morning and evening twilights merge into one doesn't occur at the poles and so is irrelevant for that latitude.
This is what it should have been considering the latitudes I was referring to. Of course, at the higher latitudes where polar night exists, then there will be no twilight, then a quick but smooth increase, then a slow decrease, then a slow increase, then a quick but smooth decrease until there is no twilight again. As the latitude increases, the changes in twilight duration will get faster and faster until they become instantaneous at the poles.
This bit explains what happens at the solstices as the latitude varies.
I think the actual point here is not the inclusion of the graph, but about the inclusion of the interesting phenomena resulting from civil twilight that is shown in the graph. So maybe if a section on this phenomena is added to the article, the graph can be added there; if not though, the article should still mention the phenomena, as it is solely based on twilight. Hope this helps. Set Sail For The Seven Seas 264° 4' 15" NET 17:36, 21 September 2009 (UTC)
Type of twilight Upper twilight limit Lower twilight limit
Civil twilight < -0°50' (sunrise/sunset) <= -6°
Nautical twilight < -6 <= -12
Astronomical twilight < -12 <= -18
Has anyone considered that "X technical twilight, xx.x hrs" is shorthand for "X twilight or worse for xx.x hours"? A length of evening twilight graph should max out at 12 hours (with a note to explain this) to keep the (nonexistant?) morning graph a mirror image of the evening. You can't start assigning all eternal twilight hours to evening just cause you want it to show 24, otherwise you can get the ridiculous notion that evening technical twilight occurs simulaneously with sunrise. Now what should be the cutoffs, mean local midnight and noon or actual? Sagittarian Milky Way ( talk) 07:29, 22 September 2009 (UTC)
I agree with the limits for the various forms of twilight, though I'd probably think of it more like this.
Definition | Position of sun |
Night | more than 18° |
Astronomical twilight | 12°<AT<18° |
Nautical twilight | 6°<NT<12° |
Civil twilight | -0°50'<CT<6° |
Day | sun above the horizon |
Also, the boundaries are marked by the various dawns and dusks or sunrise and sunset.
But for people without an intuitive knowledge of twilight this would be very misleading. It just needs a retitiling. "Hours of usable natural light". This would be useful in gauging how bright a night is at summer. Even so, reversing the hours might be slightly more useful for showing number of observable hours -- it would tell me that at Anchorage where many people live (for example), the sky would be bright enough to play baseball for pretty much the entire night, which is, needless to say, annoying. Sagittarian Milky Way ( talk) 01:57, 24 September 2009 (UTC)
I think at this point I can agree with removing technical twilight, as things should indeed be a simple as possible, but not simpler, otherwise we end up with a spherical cow!
One other thing about the graph, it should show the total amount of twilight per day, that's why morning twilight and evening twilight should be added up, as has been done with the existing graph. Also, I think Sagittarian Milky Way has a good point about this. Both twilights should be included otherwise it is not the total amount of twilight. Hope this helps. Set Sail For The Seven Seas 243° 43' 15" NET 16:14, 22 September 2009 (UTC)