Talk:New moon

message: What's all this religious mumbo in an astronomical article? If there is astrological, traditional, religious or superstition aspect to the topic - this should be completely separate section at the end.
: Please read this talk thread  Jaredscribe (talk) 06:25, 14 April 2021 (UTC)
thread_title: Religious slant

message: The picture at the top of the page doesn't have any context. It could be interpreted as an indication of what time of day different moon phases occur every day. The moon takes roughly 29.5 days to pass through each phase.
It would be a good idea to actually note what this diagram is indicating.--Jcvamp 19:28, 3 August 2006 (UTC)
replies: text: not to mention being just plain silly looking, it's just a circle in a square for crying out loud....maybe a photo of the actual event (a new moon) would be better  — Preceding unsigned comment added by 192.158.48.16 (talk) 12:18, 14 August 2015 (UTC)
thread_title:  The Picture 

message: How many days does the new moon last?
:In an astronomical sense, New Moon occurs at the instant when the Moon is in conjunction with the Sun. It's not a range of times. 
:This is why published information shows a date and time of New Moon. It's unlikely that anyone would see the Moon at its closest approach to the Sun (unless there's a Solar Eclipse), so it's become conventional to call the first visible crescent moon 'New Moon' - but this may be a day or two after the actual instant of New Moon. Pavium 07:49, 28 April 2007 (UTC)
thread_title:  How long does it last? 

message: Here's how to derive the expression for the time of mean New Moon from Delauney's parameter D (= mean longitude of Moon - mean longitude of Sun).  Apparently this is not trivial to most astronomers contributing in the Wikipedia.  I don't want to clutter the main page so I put it here on Talk.
From J.Chapront, M.Chapront-Touzé, G.Francou: "A new determination of lunar orbital parameters, precession constant and tidal acceleration from LLR measurements", A&A 387, 700..709 (2002) , Table 4:
D = 297°51'00.6902" + 1602961601.0312"×t − 6.8498"×t2 + 0.006595"×t3 − 0.00003184×t4
Converted to revolutions (i.e. divide by 60×60×360):
D = 0.8273616437 + 1236.8530872154×t − 5.2853E-6×t2 + 5.089E-9×t3 -24.57E-12×t4
derivative:
v = 1236.8530872154 − 10.5707E-6×t + 15.266E-9×t2 − 98.27E-12×t3 revolutions per Julian century (of 36525 days)
= 1236.8530872154 × (1 − 8.54643E-9×t + 12.343E-12×t2 − 79.45E-15×t3)
So the polynomial for the length of the synodic month around epoch J2000.0 is: 
(36525 d/cy) / [ 1236.8530872154 rev/cy × (1 − 8.54643E-9×t + 12.343E-12×t2 − 79.45E-15×t3) ]
= 29.530588860986 (d/rev) / (1 − 8.54643E-9×t + 12.343E-12×t2 − 79.45E-15×t3)
This has the form p/(1−f), and to first order of approximation this can be re-written as p×(1+f) .  This is accurate for our purpose because f is very small (8 orders of magnitude smaller than the main term): 
P = 29.530588860986 + 252.381E-9×t − 364.49E-12×t2 + 2.346E-12×t3
Change unit from t (Julian centuries of 36525 days) to N (lunation of 29.530... days) by multiplying by (29.530.../36525)n : 
P = 29.530588860986 + 204.051E-12×N - 238.26E-18×N2 + 1.2400E-21×N3
D is 0 modulo 1 after (1−0.8273616437)×29.530588860986 = 5.098112 days after the epoch.  Integrating now with this offset as the integration constant yields:
d = 5.098112 + 29.530588860986×N + 102.026E-12×N2 - 79.42E-18×N3 + 310.0E-24×N3
N=0 for the first mean New Moon in 2000, and that is actually the epoch of the formula.  At that time (0.17262308 revolutions after J2000) the period has already increased to 29.530588861021 days, so round to 10 decimals.   
Add 0.5 days to the constant to shift the zero point to midnight instead of noon (epoch 2000.0 is JD 2451545 falls at noon), and subtract 0.000451 days to correct for light time as explained on the main page: this yields 5.597661 days after midnight of 1 Jan. 2000 (TT).
Compare Meeus' formula ("Astronomical Algorithms", formula 47.1) derived from the ELP2000-85 : 
JD = 2451550.09765 + 29.530588853×k + 0.000 1337×T2 - 0.000 000 150×T3 + 0.000 000 000 73×T4
The quadratic term from Meeus when expressed in lunations becomes 133.7E-6×(29.530.../36525)2 = 87.40E-12, and this is indeed 14.63E-12 smaller than the newer expression, as deduced on the main page.
Tom Peters 23:51, 21 December 2006 (UTC)
thread_title:  The Big Secret? 

message: I hope no one minds, but I redirected New Moon (both words capitalized) to New Moon (Elliott Smith album), because it stands to reason that if someone capitalizes both words, they're looking for the album.  Notahippie76 (talk) 02:43, 28 November 2007 (UTC)
replies: text: I am undoing your change because numerous instances of a capitalized "New Moon" are already listed in New Moon (disambiguation) linked at the head of New moon, including New Moon (Elliott Smith album). — Joe Kress (talk) 04:51, 29 November 2007 (UTC)
replies: text: You're right, good call. Notahippie76 18:36, 30 November 2007 (UTC)
thread_title:  Elliott Smith 

message: Second book in Twilight saga.  —Preceding unsigned commen→t added by 24.191.100.39 (talk) 20:47, 30 December 2008 (UTC)
replies: text: This book is already listed in New Moon (disambiguation) at the top of New moon and has its own article at New Moon (novel). — Joe Kress (talk) 23:38, 31 December 2008 (UTC)
thread_title:  New Moon - Book by Stephanie Meyer 

message: The article says that new moon occurs when "the Moon ... lies between the Earth and the Sun", which is a bit woolly if you ask me. The moon's orbit is tilted roughly 5 degrees to the ecliptic, so the diagram is of course a simplification. The moon never passes exactly through the line connecting the Earth and Sun (although it gets very close to this during a lunar eclipse of the Earth) and so it is never exactly "between the Earth and the Sun".
So how do we define the new moon more accurately? I would guess that it is the lunar perihelion, i.e. the closest approach of the moon to the sun on each orbit. Can anyone clarify or confirm this?
I guess this only matters if you are interested in defining a time of new moon to quite high accuracy, which seems to crop up in some religious calendars and/or astrological calculations.JominyDave (talk) 21:18, 3 March 2009 (UTC)
replies: text: The apparent geocentric longitude of the Moon is the same as the Sun's. From Meeus, Astronomical Algorithms, 1998 Saros136 (talk) 06:18, 9 March 2009 (UTC)
replies: text: It is also not the Moon's closest distance to the Sun. The next new moon, for example, is March 26  at about 16:06 UT . Minimum Moon-Sun distance is March 23 at 15:58 UT. Solex 10.0. It's complicated by the fact that the Moon-Earth system is  moving away from the Sun at the same time. Saros136 (talk) 07:04, 9 March 2009 (UTC)
thread_title:  More precise definition needed? 

message: See Talk:Lunar_phase#Proposed_deletion_of_Lunar_phase_equation. -Trift (talk) 18:23, 24 June 2011 (UTC)
thread_title:  Alternate formula 

message: Substituted at 01:08, 30 April 2016 (UTC)
thread_title: Assessment comment

message: I'm having trouble rendering the first sentence of the article into meaningful English.  "In astronomy, new moon is the first phase of the Moon, when it orbits not seen from the Earth, the moment when the Moon and the Sun have the same ecliptical longitude.[1] The Moon is not visible[note 1] at this time except when it is seen in silhouette during a solar eclipse when it is illuminated by earthshine. See the article on phases of the Moon for further details."  Is it perhaps supposed to say "when its orbit is not seen from the Earth"? Thanks. --Thistledowne (talk) 17:06, 28 March 2017 (UTC)
thread_title:  Engrish? 

message: Hello fellow Wikipedians,
I have just modified one external link on New moon. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
*Added archive https://web.archive.org/web/20070202170802/http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/deltaT.html to http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/deltaT.html
When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.
Cheers.—InternetArchiveBot (Report bug) 21:04, 21 January 2018 (UTC)
thread_title:  External links modified (January 2018) 

message: This article has been factually misleading for quite a while.  The Babylonian, Hebrew, and Chinese calendars are lunisolar, and shouldn't be put in the same category as the Islamic lunar calendar.  I'm going put an  tag for half an hour and reorganize the article.Jaredscribe (talk) 20:23, 13 April 2021 (UTC)
replies: text: , my apologies, I've only just seen this notice. By pure coincidence, I happened on this article and thought 'what a horrible mess' and dived in. Feel free to revert my changes if it helps your clean up. --John Maynard Friedman (talk) 00:06, 14 April 2021 (UTC)

text: I agree broadly with your main point, but I don't agree that the Rosh Hodesh article (and its equivalent articles for other religions) is a WP:FORK. The beauty of Wikipedia is that it is not a book: the narrative does not have to be linear, it can be a multi-dimensional Russian doll. So the top level article should summarise the religious customs and beliefs associated with a natural phenomenon and these can be fully detailed in their dedicated articles. [But there is no excuse for crass errors like you found re the Islamic year]. By the way, this is equally true of more detailed scientific explanations: this summary article should not get into the details of gravitational bending or neutrino opacity. I don't see that this is being "mainstream" as you put it, but rather than that it aims for a logical, layered structure that facilitates 'drilling down'. Otherwise the result is that visitors decide wp:too long, didn't read and abandon, which we definitely don't want.--John Maynard Friedman (talk) 09:57, 14 April 2021 (UTC)
replies: text:  Agreed with  that TLDR is a potential problem.  WP:SUMMARYSTYLE is good overview of the WP structure you describe as "multi-dimensional russian doll".  I retract my concerns about WP:FORK.  For section #Hebrew calendar, #Chinese calendar, etc. I'd like to see more on the cultural, traditional, or religious new moon practices and observances, more so than on the calendar system generally, but this latter can be excerpted.Jaredscribe (talk) 00:59, 22 April 2021 (UTC)

text:  Also, since this is a teachable moment -  I fully support WP:Verify standards and use of scholarly sources.  I criticise "scientism" when it becomes a popular way of uncritically relying on certain conclusions of western academia to justify scoffing at Asian civilizations (and Judaism) as "lunatic charlatans" without even understanding them, while failing to think critically about Islam or understand what a lunatic really is.  And prior to April 2021, this article incorrectly lumped #Chinese calendar, #Hindu calendar, and #Hebrew calendar, which are actually lunisolar calendars and the #Bah'ai calendar which is is solar, in with the Islamic lunar calendar.  The "solarian" POV in the west - that of the Roman empire, the kingdoms of Europe, the "catholic" church, and the secular modernism that supposedly replaced it - is reflected in Academia and on wikipedia, and is not neutral.   Science is good, ignorant prejudice is not.  I'm not WP:SOAPBOXing for lunisolarians or lunatics here, so much as working to restore WP:NPOV.  Jaredscribe (talk) 01:23, 22 April 2021 (UTC)
replies: text: User:John Maynard Friedman, User:Jaredscribe: I drop in late, after not working on Wikipedia for several years. I think a "solarian" POV is a non-issue. Different calendars of different types are and have been in use for millennia, and AFAIK any discussion on which is "better" is rather academic and depends on which criteria that you like best. We don't need al this polarization: just factually describe what is in use. That said, I now propose to remove the religious calendar details altogether from this article, and just link to the separate pages that describe them. Tom Peters (talk) 14:12, 8 August 2022 (UTC)
thread_title:  Separating sections: Lunisolar Calendar and Lunar Calendar

message: I removed this material per WP: NOTMANUAL. Perhaps someone will find a better home for it?
Action taken by --John Maynard Friedman (talk) 00:07, 14 April 2021 (UTC)
thread_title: Instructions removed per NOTMANUAL

message: Per MOS:ERA, the era notation (AD/BC v. CE/BCE v AM v AH etc) should not be changed unless there is a consensus that the pre-existing notation  is inappropriate to the article and should be changed. Given that the new moon as defined by sighting of the first crescent is especially significant in Islam and Judaism but only marginally so in Christianity, and that the article discusses its significance to the Baháʼí Faith and Buddhism, it seems to me to be invidious to retain the Christian notation in preference to any of the others. Accordingly I propose that the article uses the neutral CE/BCE notation. Are there any objections? --John Maynard Friedman (talk) 18:54, 14 April 2021 (UTC)
thread_title:  Era notation 

message: For most readers of this article the section on lunation numbers immediately after the lede is probably rather esoteric. I propose to move this section to the bottom of this article for those users who are actually interested in counting individual new moons in the calendar of their choice. AstroLynx (talk) 11:16, 3 May 2021 (UTC)
thread_title:  Lunation numbers 

message: I worked on this page way back (and most of my contributions have been removed). I now see that in the past few years a lot of text has been added about various calendars that happen to have a lunar month.  While respecting the effort that went into that, I think this is mostly off-topic, because this article is about the New Moon lunar phase and not about religious calendars in detail.  So I propose to remove the elaborate texts and just add a list of (religious) calendars - possibly classified as lunar, lunisolar, solar as they are now - with wikilinks to the pages that deal with them in detail. 
Tom Peters (talk) 12:28, 8 August 2022 (UTC)
replies: text: Disagree. The discussion above, to me, make good arguments regarding WP:WORLDVIEW to keep the text. However, I do agree with you that much of the text is off-topic. I think that the text should be refocused to be about the significance/use of the new moon in said various calendars as there's a bit of extraneous text about the calendars themselves. EmeraldRange (talk/contribs) 18:06, 6 January 2023 (UTC)

text: I disagree too. If there were any significant deviations into WP:fork territory, I would agree with a cull but I don't see anything obvious. All seem to about the significance, the special significance, of the New Moon in determining the operation of the calendar. If the article were to be restricted to the field of astronomy, it would be very thin indeed: as astronomical phenomena go, it is pretty trivial. Its real interest is the way that it has determined human timekeeping for millennia. --𝕁𝕄𝔽 (talk) 23:47, 6 January 2023 (UTC)
thread_title:  Remove elaborations on calenders?