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Cyberseeker
2016-Mar-03, 01:37 AM
Statement and question: :think:

When ancient calendar keepers identified 'new moon', it was when an eye witness actually saw the start of the crescent forming. So the the first day of their month started a day or two after dark moon. However, if you ask a modern observatory for 'new moon' they will give you the date of 'dark moon.' As far as they are concerned it is the same thing.

Am I correct in the above statement, or is it an incorrect assertion? An answer would be appreciated.

Hornblower
2016-Mar-03, 03:36 AM
Statement and question: :think:

When ancient calendar keepers identified 'new moon', it was when an eye witness actually saw the start of the crescent forming. So the the first day of their month started a day or two after dark moon. However, if you ask a modern observatory for 'new moon' they will give you the date of 'dark moon.' As far as they are concerned it is the same thing.

Am I correct in the above statement, or is it an incorrect assertion? An answer would be appreciated.

I would say your statement is correct.

molesworth
2016-Mar-03, 05:41 PM
Hmmm, or maybe not...

It's very hard to know for sure, as the records can't (as far as I know) be tied exactly to dates in any kind of modern calendar. However, since the new moon is visible during daylight, it could be just as valid to say that it was the day of the moon between a waning and waxing crescent.

Cyberseeker
2016-Mar-03, 07:54 PM
In any case, astronomers in today world, simply use 'dark moon' and 'new moon' interchangeably? Yes?

ngc3314
2016-Mar-03, 07:55 PM
The only use of the first would be in "dark of the Moon" or "dark time", both only loosely defined to be when moonlight is not strong enough to interfere with observation of faint objects. Among observational optical astronomers, I haven't encountered "dark moon".

StupendousMan
2016-Mar-03, 11:49 PM
Among observational optical astronomers, I haven't encountered "dark moon".

+1

01101001
2016-Mar-04, 12:22 AM
As far as they are concerned it is the same thing.

Well if you explained that different disciplines use the 2 phrases to identify different events, the astronomer might be briefly interested in that usage of astrologers and religionists and ancient mariners

But then they'd continue to use the more modern meaning of "new moon".

Jeff Root
2016-Mar-04, 01:00 AM
Like the others, I have never heard the term "dark moon" used to
refer to the new moon. The unambiguous astronomical term for
"new moon" is "lunar conjunction". The equivalent to "full moon"
is "lunar opposition".

You can search for these terms.

-- Jeff, in Minneapolis

George
2016-Mar-04, 04:32 PM
Since the Moon is always half dark (varying in darkness with phase angle due to Earthshine), I'm not surprised "dark moon" is not used.

Whether ancient or not -- there are some still using lunar calendars -- the beginning of the lunar month varies from one country to another. Some use a "new moon" as Jeff shows, meaning at the time of lunar conjunction, another uses the first sighting of the crescent (e.g. Hebrew), and another, apparently, might use the day after a "full moon". Lunar calendars (https://en.wikipedia.org/wiki/Lunar_calendar).

Extravoice
2016-Mar-04, 05:05 PM
The only time I've heard of "dark moon" is in this old song:

Was the dark of the moon on the sixth of June
In a Kenworth pullin' logs
Cab-over Pete with a reefer on
And a Jimmy haulin' hogs...

--Convoy by C.W. McCall

Jeff Root
2016-Mar-04, 05:26 PM
The expression "dark of the moon" is common and familiar, but
it isn't synonymous with either lunar conjunction or new moon.
I think it most commonly refers to the period of time around new
moon when the Moon isn't visible. But it might refer to any time
that the Moon is not visible at night, or as George suggests, the
night side of the Moon at any time on Earth.

-- Jeff, in Minneapolis

fagricipni
2016-Mar-05, 11:05 PM
You are correct on the distinction on the ancient meaning of "new moon" and the modern meaning of "new moon". I, too, have used the phrase "dark moon" to refer to the modern astronomical definition of "new moon" when talking about the calculation of the date of Easter; the astronomical new moons can not be directly compared to the "ecclesiastical new moons" referred to in discussions of the calculation of Easter because the "new moon"s refer to different events.* The Hebrew and Islamic calendars also use first visibility of the crescent moon after sunset to be their "new moon". (However, the modern Hebrew calendar is no longer observational; ie, the date of the "new moon" is calculated rather than directly observed nowadays.)

But I have to say that others are correct in that I have never seen anyone else use the term "dark moon" for the modern astronomical definition of "new moon" until this thread. So based on the comments of this thread, you would have to define the terms before freely using them.

* There are several complications in comparing these "ecclesiastical new moons" to astronomical "new moons"; this reference to different events is but the first of the complications. One might think that one could compare the "ecclesiastical full moons" to astronomical "full moons" to see how accurate an approximation the "ecclesiastical system" is, but then there is the complication of time zones. The "ecclesiastical moons", both "new" and "full" are simply dates without reference to any particular offset from UT, the astronomical moons occur on different dates depending on one's offset from UTC. Neither UTC nor time zones nor even a standard 0 meridian existed in 1582 when the rules for the modern calculation of Easter were laid down, so it is difficult to say exactly how they should be compared; the only hint I can find is that occasional proposals attempt to reconcile the Eastern Orthodox Easter with the Gregorian Easter by using astronomically accurate calculations of the vernal equinox and (astronomical) full moon at the meridian of Jerusalem. One has to define an offset from UT to determine whether it is Sunday when the full moon occurs.

Cyberseeker
2016-Mar-06, 01:30 AM
The consensus here seems to be that I am using a relatively unknown term 'dark moon' for what should properly be called 'lunar conjunction.' Thanks for your responses. :) However, I got the term from a reputable lunar software site called Hermetic Systems. (http://www.hermetic.ch/cal_stud/hlwc/hlwc.htm) On this page the writer, Peter Meyers, says, "A dark moon occurs when the Sun and the Moon are astronomically conjunct (or more exactly, when either the Moon's center lies on the line joining the centers of the Earth and the Sun or the plane defined by the Sun, Earth and Moon is perpendicular to the Earth's orbital plane)." Perhaps Mr Myers uses a terminology that is not always used in astronomical circles. (I dont know; Im a just layman)

In any case, at least two calendars (the Jewish and the Arabic) still use the first faint visible crescent rather than lunar conjunction to start the first day. Does anyone know if it is still identified by a physical sighting? Or is it mathematically estimated, then offset from the conjunction?

fagricipni
2016-Mar-06, 02:55 AM
"A dark moon occurs when the Sun and the Moon are astronomically conjunct (or more exactly, when either the Moon's center lies on the line joining the centers of the Earth and the Sun or the plane defined by the Sun, Earth and Moon is perpendicular to the Earth's orbital plane)."

Yes, that does appear to be a correct definition of ecliptic conjunction which is what is commonly given as the new moon nowadays.


In any case, at least two calendars (the Jewish and the Arabic) still use the first faint visible crescent rather than lunar conjunction to start the first day. Does anyone know if it is still identified by a physical sighting? Or is it mathematically estimated, then offset from the conjunction?

In the Jewish calendar as currently used, the lunar cycle is approximated (and then adjustments are made to prevent certain holidays from occurring on certain days of the week). As I said above the current Jewish calendar is computational. The Islamic calendar is observational; it depends on actual observation of the first crescent. (Or is supposed to; I have read that Saudi Arabia uses a computational approximation for its official national calendar.)

Jeff Root
2016-Mar-06, 03:40 AM
In my opinion the term "new moon" best fits the first sighting of
the crescent moon after conjunction. But in everyday common
usage in the USA during my entire lifetime it has always referred
to the time of conjunction. Last I saw -- a couple of decades ago --
the new moon was looked for by Islamic observers in whatever
occupied location was nearest to the location on Earth where it
was expected to first be visible. I think (I may have read or heard
this) that the date of the new moon is the date at Mecca at the
moment of the sighting.

-- Jeff, in Minneapolis

01101001
2016-Mar-06, 03:54 AM
However, I got the term from a reputable lunar software site called Hermetic Systems.

What is its repute? Hermetic's earliest meaning is related to the occult, alchemy, astrology, and theosophy.

The site self-describes being about "[...] make available the software developed by Peter Meyer, a professional software developer with an MPhil degree in computational physics (but better known as the developer of software for Terence McKenna's Timewave Zero theory)."

So they seem determined to throw their own name on the trash heap.

Centaur
2016-Mar-06, 04:41 PM
Traditionally New Moon referred to one's first sighting of the waxing crescent moon after solar conjunction. It's what I call that sighting. I refer to the conjunction as Dark Moon, which is a shortened version of Dark of the Moon. That's how the terms are used in the calendars and articles on my Moon webpage: www.CurtRenz.com/moon.html

Of course most English language calendars post the date of conjunction as that of the New Moon. Actually that moment marks the end of the Old Moon and the beginning of the New Moon. I especially like the expression "Old Moon in the New Moon's Arms", which refers to the effect of earthshine on the night side of a waxing crescent moon. Application of the term New Moon appears reasonable for about two days after Dark Moon. On the third day the Moon is called "Diana's Bow" in reference to the archery equipment of the ancient Roman Goddess of hunting and the Moon

Cyberseeker
2016-Mar-06, 05:35 PM
Thanks for all the responses and clarifications. :)

The reason for my query is because I am looking to find astronomical solutions to the elusive date of the crucifixion. We know that Pilate governed Judea from AD 26 to AD 36, so it must have been somewhere in-between – but exactly when?

This is a historical issue, but it fits Cosmoquest forum because several astronomical problems hinder a simple fixing of Jesus’ last Passover date. The 'New Moon' question is one case in point. I have worked out a chart that shows the alternative possibilities between AD 26 and AD 36. It is not my intention to introduce history and theology here, but I may post up my chart on a new thread if anyone is interested in checking my lunar calculations.

Jeff Root
2016-Mar-06, 07:19 PM
I either had forgotten or possibly was never aware that the date
has not been pinned down. I'm surprised. It's the sort of thing I
would have tried to do myself if I'd been aware of it and thought
enough information was available to deduce it.

-- Jeff, in Minneapolis

Centaur
2016-Mar-06, 08:01 PM
I either had forgotten or possibly was never aware that the date
has not been pinned down.

Thatís because the events portrayed in the gospels were not confirmed by the contemporary historians or the meticulous Roman records of legal court proceedings, sentences and executions. Hence Cyberseeker appears to be hoping that verifiable astronomical events will somehow help him uncover some evidence.

fagricipni
2016-Mar-08, 06:38 AM
Dating of the crucifixion astronomically (https://en.wikipedia.org/wiki/Chronology_of_Jesus#Astronomical_analysis) is an exercise that has been tried by others as well. However, it is not a simple matter of calculating the Jewish calendar back: the current Jewish calendar is computational, but it has not always been that way. Also, the conditions for the intercalation of the extra month were not always purely based on astronomical considerations but biological considerations as well; if I recall correctly it was the ripening of the barley and weaning of the lambs that served as the non-astronomical considerations in deciding whether to add an extra month, but don't rely on those being the correct signs.

Also, there is the argument among some historians that Jesus never existed as an actual person. I won't get in to that debate, but I will point it out as a position held by some historians.

Cyberseeker
2016-Mar-08, 03:59 PM
the current Jewish calendar is computational, but it has not always been that way. Also, the conditions for the intercalation of the extra month were not always purely based on astronomical considerations but biological considerations as well; if I recall correctly it was the ripening of the barley and weaning of the lambs that served as the non-astronomical considerations in deciding whether to add an extra month, but don't rely on those being the correct signs.


My topic thread for discussing these aspects (http://cosmoquest.org/forum/showthread.php?160399-The-Moon-and-New-Testament-Passover-Dates) has been closed. I have submitted an edit to the moderators, and if they reopen it I'd be happy to discuss the old intercalation method there.

Centaur
2016-Mar-09, 03:01 AM
Also, there is the argument among some historians that Jesus never existed as an actual person. I won't get in to that debate, but I will point it out as a position held by some historians.
+1