Finding North from unclear sky around New Year.

 

Finding North from unclear sky around New Year.

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

(Blog No.121).

#find North, #finding North, #direction, #by stars, #Sirius, #Canopus, #Orion-Rigel, #Capella, #New Year, #unclear sky
Around New Year there are some bright stars shining the whole night. They include Sirius, Canopus, Orion-Rigel and Capella. These four stars can be used to locate the Celestial poles in the sky and subsequently the terrestrial principal directions.

1. Celestial poles and terrestrial directions.

Sun on Celestial Sphere

Figure: The Sun, the Moon and the stars are attached to a Celestial sphere which encloses the Earth like a giant rotating cage.

To an Earth bound observer, the Earth appears to be enclosed by a large rotating spherical shell called the Celestial Sphere with all stars attached to it. This shell rotates around the Earth nearly one revolution every 24 hours. This rotation leaves unmoved only 2 points on the shell. They are called the Northern and Southern Celestial poles of the Celestial Sphere.

If an observer can locate one Celestial pole then the projection to the ground of the line from him to the pole will be along his terrestrial North South direction.

2. Locating the Northern Celestial Pole.

Orion by Samsung GN2

Figure: Photo of the Orion constellation (Photo added 2018 May 09). Northern Celestial pole is from the top direction of this photo.

An Earth bound observer in Northern hemisphere or on the tropical zone can identify the Orion constellation around New Year. The front foot of the hunter represented by this constellation is the bright star Orion-Rigel. The trailing shoulder of the hunter is the bright star Betelgeuse.

The brightest star in the sky is Sirius. The great circle arc Sirius to Capella is 70 degrees long with Betelgeuse being close to its midpoint.
Extending the great circle arc Orion-Rigel to Capella to 100 degrees long bring us practically to the Celestial North pole.

star map mercatorx1p6

Figures 1a, 1b: The Mercator maps of the sky for inhabitants of Tropical Zone. North direction is on its top. 24hr of R.A. is near the center and R.A. increases towards the left (East) of the map. The map is to be read South side up in the Southern hemisphere.

3. Locating the Southern Celestial pole.

An Earth bound observer in Southern hemisphere or on the tropical zone can identify the Orion constellation around New Year. Sirius is the brightest star in the sky and it is behind the trailing foot of the hunter.
Canopus is the next brightest star within 45 degrees of Sirius. The great circle arc Sirius to Canopus is nearly 35 degrees long. Doubling this arc bring us practically to the Southern Celestial pole.

Bright Stars 20 Plus 2

Figure 2: Table of 20 brightest +2 stars in order of appearance.
4. Visibility of these four stars.
The four stars appear on the meridional line (the North South line through the zenith of the observer) near midnight of New Year.
They appear two hours earlier for each additional calendar month after that date.
Example:
In April, they appear on the meridional line at about 24 hr – (2 hr)×(4th-1st) = 18 hr. After 18 hr they slowly move to the setting (Western) side.

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When is Lunar New Year? (Khi nào là Tết Âm Lịch?)

 

When is Lunar New Year? (Khi nào là Tết Âm Lịch?)

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

(Blog No.103).

#find North, #finding North, #Lunar calendar, #New Year, #Tết, #Âm Lịch, #Tết Nguyên Đán , #Tết Nguyên Tiêu,

When is Lunar New Year? (Khi nào là Tết Âm Lịch?)

To many Western and Vietnamese people, it is hard to tell when East Asian Lunar New Year (Tết Âm Lịch in Vietnamese) will come.

This blog gives an easy answer to that question.

1. The time for East Asian Lunar New Year.

The New Year begins with a New Moon. Each Lunar month span from one New Moon to the next one.

The month enclosing the December Solstice time (in December 21st) is defined to be the second last Lunar month of the year.

After that is one last month of the year and then comes the New Year Festival.

The rule gives people adequate time (more than one Lunar month) to prepare for the festival.

2. Example for 2018.

On the Solar New Year for 2018, the Moon was full. It was the 15th day of some Lunar month. Ten nights prior to that was the December Soltice (on December 21st). That night was the 5th night of that some Lunar month. That Lunar month is defined to be the second last (11th) month of the Lunar year. So the Solar New Year night was the 15th night of the 11th Lunar month.

Therefore the beginning of last Lunar month of the year is around Jan. 14th, while Lunar New Year is 29.5 days after that and is around Feb. 12th of 2018.

3. Tết Nguyên Đán and Tết Nguyên Tiêu.

The first New Moon in each Lunar year is called “Tết Nguyên Đán” in Vietnamese and the Full Moon following it is called “Tết Nguyên Tiêu”  (many Vienamese don’t know the words “Tết Nguyên Tiêu”), or more commonly “Lễ Hội Rằm Tháng Giêng”.

Ancient Chinese historical texts made many references to (yearly) First Full Moon Festivals but it is very hard to find any mention of (yearly) First New Moon Festivals.

So Chinese people have been celebrating the yearly Festivals of First Full Moon (with Moon lit nights). When and why the Festivals of First New Moon (with dark, stars lit nights) became more celebrated than the Festivals of First Full Moon is an interesting question.

It is seen in the following two figures that at Lunar New Year, the bright star Leo Regulus crosses the meridional plane near to midnight. At First Full Moon Festival, Leo Regulus crosses the meridional plane about 1 hour before midnight while the Full Moon crosses the meridional plane at midnight.

equatorial stars

Figure: Stars in tropical zone for beginners (Tropical zone). Click to enlarge figure.

Bright Stars 20 Plus 2

Figure 2: Table of 20 brightest +2 stars in order of appearance.

4. Neighbouring countries may have their Lunar New Years differing by one month.

a. Soltice time can be accurately determined by watching the direction of the setting (or rising) Sun. When the azimuth angle of the setting Sun is plotted for consecutive days near solstice time it shows an increase then decrease (or the other way around). The time for the turn-around is the accurately determined solstice time. Solstice time is a global event and is the same for all locations on Earth.

b. New Lunar month begins on the day preceeding the night with the first view of a thin crescent on the trailing side of the  Moon (an initial New Moon.). New Lunar Month is a local event. The beginnings of new Lunar months differ for different locations on different longitude of the Earth.

c. It is rare occasions but we can sometimes observe that one country A begins its New Moon just before solstice while its neighbour B on the next time zone begins its New Moon just after solstice.

Therefore for the next Lunar month, country A is still in Lunar month 11 while its neighbour B is on is already in Lunar month 12.

Consequently country B has its Lunar New Year one Lunar month ahead of country A.

d. The months in these two countries will get synchronized again when the astronomical event marking Lunar month 2 falls into the Lunar months of both countries.

Example: Vietnamese (time zone +7) Lunar New Year in 1984 was earlier than Chinese (time zone +8) New Year by one Lunar month.

5. Neighbouring countries may also have their Lunar New Years differing by one day.

New Lunar month begins on the day preceeding the night with the first view of a thin crescent on the trailing side of the  Moon (an initial New Moon.). New Lunar Month is a local event. The beginnings of new Lunar months differ for different locations on different longitude of the Earth.
It is rare occasions but we can sometimes observe that one country A see no Moon for the night while its neighbour B on the next time zone sees a New Moon just before Sunrise.
Therefore for the next whole Lunar month, country A is behind its neighbour B by one Lunar calendar day.

If this happens at the end of a Lunar year, the Lunar New Year day of country A will be behind the Lunar New Year day of country B by one day.

Example: Vietnamese (time zone +7) Lunar New Year in 2007 was earlier than Chinese (time zone +8) New Year by one day.

References.

[1]. tonytran2015, Simple-determination-of-east-asia-lunisolar-new-year , posted on 2017 January 19th.

[2]. http://www.bbc.com/vietnamese/vietnam/story/2006/07/printable/060704_lichvietnam.shtml

[3]. https://m.thanhnien.vn/van-hoa/vi-sao-nam-nay-viet-nam-an-tet-truoc-trung-quoc-mot-ngay-317188.html

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Was New Year night chosen to have Sirius highest at midnight?

Was New Year night chosen to have Sirius highest at midnight?

by tonytran2015 (Melbourne, Australia).

Click here for a full, up to date ORIGINAL ARTICLE and to help fighting the stealing of readers’ traffic.

(Blog No.102).

 

#find North, #finding North, #bright  star, #navigation, #Sirius, #New Year,

Was New Year night chosen to have Sirius highest at midnight?

When looking at the dates of the brightest stars, we cannot overlook the fact that the brightest star Sirius is highest on the Midnight of January 1st.

The question is was that the reason why January 1st was chosen on that date?

This question invites our thinking on ancient astronomy and time keeping.

The brightest stars and their dates are given in the following two figures.

Equatorial Stars2

Figure: Stars in tropical zone for beginners (Tropical zone). Click to enlarge figure.

Bright Stars 20 Plus 2

Figure 2: Table of 20 brightest +2 stars in order of appearance.

References.

[1]. tonytran2015, Finding North direction and time by stars, survivaltricks.wordpress.com, https://survivaltricks.wordpress.com/2015/08/28/finding-north-and-time-by-stars/ , posted on August 28, 2015.

[2]. tonytran2015, Finding North and time by stars in the tropics, survivaltricks.wordpress.com, https://survivaltricks.wordpress.com/2016/05/25/finding-north-and-time-by-stars-in-the-tropics/, posted on May 25, 2016

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