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desertstars
Deja moo
Reged: 11/05/03
Posts: 30031
Loc: Tucson, AZ
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This question popped up in the Beginners forum today. (See post #2373105 - next to last at this point.) I don't have an answer, so I thought I'd turn the Lunie Bin loose on it. (If you have an answer, please post it in Beginners as well as here.  )
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Tom W.
SVP8 'She turned me into a 3-legged Newt' EQ
Ralph, the All-Purpose 102mm Refractor
Under the Desert Stars
Alcohol and calculus do not mix. Please don't drink and derive.
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Tim2723
The Moon Guy
Reged: 02/19/04
Posts: 5121
Loc: Northern New Jersey
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Where's Curt?
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The crwth will set you free!
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desertstars
Deja moo
Reged: 11/05/03
Posts: 30031
Loc: Tucson, AZ
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Quote:
Where's Curt?
Good thinking!
Earth to... Oops...
I mean, Moon to Centaur, come in Centaur... 
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Tom W.
SVP8 'She turned me into a 3-legged Newt' EQ
Ralph, the All-Purpose 102mm Refractor
Under the Desert Stars
Alcohol and calculus do not mix. Please don't drink and derive.
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Centaur
Pooh-Bah
Reged: 07/12/04
Posts: 1123
Loc: Chicago
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The New Moon in the Old Moon’s Arms is not a common expression, although I see how it can be given meaning. The far more famous old expression refers to the Old Moon in the New Moon’s arms.
Originally the term New Moon referred to the slender waxing crescent seen in the evening sky a day or two after its conjunction with the Sun. The day of conjunction was referred to as that of the Dark Moon. Most modern calendar makers tend to label the day of conjunction as that of the New Moon, which leads to an ambiguity. I prefer the older definitions.
On the day of conjunction (Dark Moon) the Earth would appear full to an observer on the Moon. During the days on either side the Earth would appear nearly full. The earthshine during that period is bright enough to make the night portion of the Moon visible on Earth. During the days following the Dark Moon it appears that the New Moon’s crescent is partially circling a dim version of what had once been a gibbous Moon shortly after the previous Full Moon (hence, the Old Moon). This effect is popularly known as the Old Moon in the New Moon’s Arms. It is best exemplified by a two or three-day old Moon seen in a dark sky as twilight is ending. See the photo below which I took on 2007 MAY 17 of the Moon aged 1.28 days.
I can see how a similar effect during the days before Dark Moon could be called the New Moon in the Old Moon’s Arms, but that expression does not have much currency.
Roger Sinnott, rsinnott@skyandtelescope.com, of Sky & Telescope magazine is someone who collects and disseminates data on New Moon spotting. For information on the International Astronomical Union’s Central Bureau for Astronomical Telegrams, go to: http://cfa-www.harvard.edu/iau/cbat.html
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For astronomical graphics, including
monthly wallpaper calendar, visit:
www.CurtRenz.com/astronomical.html
Curt Renz - "Centaur"
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Tom,
Your main question, I think, had to do with to whom crescent sightings should be reported.
In addition to Sky and Telescope, two organizations I'm aware of that collect and collate such observations, perhaps in a more systematic way than S&T, are the Moon Watch program, currently run by the UK's Nautical Almanac Office, and the Islamic Crescents' Observation Project (ICOP).
I'm not sure if the former is still active since they haven't posted any reports since last year; but the latter definitely is. ICOP welcomes reports from Muslims and non-Muslims alike. To see their collection of reports from the last 10 years click the "Crescents" button in their toolbar and select "Moon Sighting Results". They are organized by month and year according to the Islamic calendar (we are currently in year "1429"), but the reports themselves (once you find the month you're looking for) are identified by western date and time. ICOP also provides carefully constructed charts indicating the likely zones of first and last visibility of upcoming new and old crescents (as well as software for doing the same at home). Moonwatch has similar utilities but only from the most recent month.
Both organizations are interested in using the observations to refine the algorithms they use to predict when lunar crescents will first (or last) be visible.
-- Jim
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desertstars
Deja moo
Reged: 11/05/03
Posts: 30031
Loc: Tucson, AZ
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Exactly what we were hoping for! Thanks! 
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Tom W.
SVP8 'She turned me into a 3-legged Newt' EQ
Ralph, the All-Purpose 102mm Refractor
Under the Desert Stars
Alcohol and calculus do not mix. Please don't drink and derive.
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Quote:
Originally the term New Moon referred to the slender waxing crescent seen in the evening sky a day or two after its conjunction with the Sun. The day of conjunction was referred to as that of the Dark Moon.
Curt,
In what centuries was this terminology used? Are you perhaps translating phrases from some other language? Could you point me to an historical example of the terms "New Moon" and "Dark Moon" having been used in this sense?
I am, of course, aware of your use of "Dark Moon", but in researching the page on lunar phases in the-Moon Wiki I did a search in Google, Google Scholar, and Google Books, and came up empty except for one obscure use of it in a table in a book from India and a statement in the Wikipedia that this is the proper historic term (but without any reference).
To the best of my knowledge, to English-speaking astronomers the term "New Moon" has always meant the moment in time defined by the conjunction in celestial longitude between Moon and Sun. The Moon's age is measured from that point. At conjunction the age is zero and hence the Moon is "New" (starting a new cycle). It seems unlikely astronomers would have used the term "Dark Moon" to refer to this moment since, until Danjon's hypothesis from the 1930's that the length of the crescent vanishes when the Moon is closer than 7 degrees from the Sun, they wouldn't have expected the Moon to go totally dark except perhaps when observing a solar eclipse at the moment of totality. And as Martin Elsässer has elegantly demonstrated in another thread, in most months it would appear that this earlier view was correct and the Moon indeed doesn't go entirely dark even at conjunction.
As indicated on the Wiki page, there are references back at least to 1726 describing the confusion that arises in English language almanacs between lay persons wanting the term "New Moon" to mean a young crescent versus astronomers using it to mean the Moon at conjunction, but "Dark Moon" is not offered as an alternative for the term. Instead there is a reference to the correct term for the first crescent visible in the new cycle (the layman's "New Moon") as being the Moon's "Ortus Heliacus" (= heliacal rising?); although to me (my Latin is nonexistent) it would seem that is describing the last crescent of the old cycle (which rises just before the Sun), and the first one seen in the new cycle would be a "heliacal moonset" (= moonset visible closest to Sun).
-- Jim
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Centaur
Pooh-Bah
Reged: 07/12/04
Posts: 1123
Loc: Chicago
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Quote:
In what centuries was this terminology used? Are you perhaps translating phrases from some other language? Could you point me to an historical example of the terms "New Moon" and "Dark Moon" having been used in this sense?
These terms were originally developed through common usage long before astronomy became a full time profession, and as the case with most professions, the inner circle developed its own jargon that may have differed from the traditions of the masses. Most words evolved through use by ordinary folks and not the dictates of the supposedly elite. In ancient times folks would not have been aware that a new lunar cycle had begun until a slender crescent was visible in the evening sky, hence the term New Moon. Dark Moon (or Dark of the Moon or Change of the Moon) referred to the period when the Moon was invisible due to its apparent proximity to the Sun.
Below are links to encyclopedia and dictionary references. If your preferred usage differs from mine, Jim, I certainly have no objection. May tonight’s New Moon near Mercury bring you happiness.
http://en.wikipedia.org/wiki/Dark_moon
http://dictionary.reference.com/browse/new%20moon
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For astronomical graphics, including
monthly wallpaper calendar, visit:
www.CurtRenz.com/astronomical.html
Curt Renz - "Centaur"
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Thanks, Curt.
As usual, it seems I popped off without doing an adequate amount of homework -- at least I find more references now than I did before. As best I can tell, the phrase "change of the moon" enjoyed a fair amount of popularity in former times as an opposite for "Full Moon" in discussions of tides (probably a pretty close equivalent to the astronomer's "New Moon"). "Dark of the Moon" has also been widely used, especially in connection with agricultural folklore, to describe the part of the month when the Moon is not visible. My dictionary says the latter phrase originated in about 1650 (as compared to "New Moon", which comes down to us from Middle and Old English). And Google reveals that "Dark Moon" has indeed occasionally been used as a shorter equivalent for "Dark of the Moon".
Using "Dark Moon" to mean "the day of conjunction" seems quite rare; and if actually used in that way it would, it seems to me, make "Dark Moon" just as ambiguous as "New Moon": does it refer to an instant or an interval? The Wikipedia page describing the New Moon, says (as you do) that to avoid confusion the term "dark moon" can be used to unambiguously describe "the astronomical new moon" (the instant of conjunction); yet the link provided there takes one to the page you referenced, explaining that "dark moon" is an interval lasting from 1.5 to 3.5 days.
It would seem to me that, given the widely-acknowledged dual meaning of "New Moon", a less ambiguous term for the first crescent that can be seen from a given location might be "First Crescent". "Young Crescent" seems good for a young, but not necessarily first, crescent. And for conjunction, using the term "Conjunction" is a possibility. But that's just a thought, and I haven't researched whether these terms have any historical precedent or not.
As to tonight's "New Moon", thanks for the good wishes; but it's totally overcast here. Perhaps that's why I'm in such an argumentative mood...
-- Jim
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kfred
Carpal Tunnel
Reged: 11/11/03
Posts: 2005
Loc: Dayton, Ohio
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Nice picture!
Fred
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River Cam - Cambridge England
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AstroRealtor
professor emeritus
Reged: 03/26/08
Posts: 538
Loc: Terra Firma
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I caught a worthwhile lengthy look at the sliver of the young moon last night. By my calculation it was the "youngest" moon I have ever seen. A personal best 35 hours and 40 minutes "old"
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Clear Skies, Jim
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Discovering: Messier objects, Deep sky treasures, NGCs, Double stars, & Nebulae of all kinds.
Televue 85 "Polaris" Mount
Custom Crafted Newtonian Dob 8" f7 w/Feathertouch
Celestron Cometron Reflector 114mm f8
Zeiss Diafun 8 X 30 Binos
Zeiss 10 X 56 Binos
 Aldrich Astronomical Society
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