(533) What is pentagram 五芒星?

  I found an article about Gobousei(五芒星) of eight Hachiman shrines in a booklet Matsuyama Hyakuten. It reads, "Interesting enough, a figure of Gobousei appears on the map by connecting these shrines with lines. Gobousei was used as a crest of Abeno Seimei..."

  What is Gobousei? And who is Abeno Seimei? I did a little research on them and now I'd like to present the report on Gobousei.
I'm going to talk about following things that I did some research.

1. What is Gobousei?
2. Abeno Seimei's crest
3. How to draw a figure of Gobousei
4. Meaning of Gobousei and others

1. What is Gobousei?
  Digital Japanese dictionary Daijisen says that it is a five-pointed star made by extending sides of a pentagon. Pentagram in English.

Merriam-Webster English dictionary says pentagram is a figure of a 5-pointed star usually made with alternate points connected by a continuous line and used as a magic or occult symbol.

2. Abeno Seimei's crest
What is a family crest of Abeno Seimei?
Abeno-Seimei-ban crest
This is an amulet for blessing and disaster relief that came from the Middle East. This crest is a talisman born from the popular belief that the devil is dismissed. The name comes from the fact that it was used by Abeno Seimei, who controls the Onmyodo, a type of magic.

ーKamon-wo-yomu by Nosaka Toshio, Best Shinsho

家紋を読む―ルーツと秘密を解き明かす (ベスト新書)

• 作者: 能坂 利雄
• 出版社/メーカー: ベストセラーズ
• 発売日: 2004/12/01
• メディア: 新書

Bold Seimei-Japanese-Bellflower crest
Fine Seimei-Japanese-Bellflower crest
正しい紋帳　古沢恒敏　編　金園　昭和58年5月30日発行

正しい紋帖―家紋・商標・県都市章5500種 (1972年)

• 出版社/メーカー: 金園社
• 発売日: 2021/05/15
• メディア: －

Fine Seimei-Japanese-bellflower crest

Who is Abeno Seimei?
  Abeno Seimei was always with Michinaga the Heian period aristocrat, and died at the age of 85 in the second year of Kanko (1005). Until his death as the oldest onmyodo magic master he protected Michinaga from many disasters.
ーOnmyou-fushigiden Youkai-zorori by Sawada Tokuko

【中古】 陰陽ふしぎ伝　妖怪ぞろり 旺文社創作児童文学／沢田徳子(著者),渡辺有一 【中古】afb

• ショップ: ブックオフオンライン楽天市場店
• 価格: 200 円

3. How to draw a figure of Gobousei
  There are two ways to construct the pentagram. One is by connecting alternate vertices of a pentagon, the other is by extending the edges of a pentagon until the lines intersect. I'd like to take the former way today.
First we draw a pentagon, a regular pentagon. The pentagram can be constructed by connecting alternate vertices of the pentagon. (Vertices are points of intersection of lines.)

  I'll show you 3 different ways of drawing a pentagon. Let them be A, B, and C, respectively.

Method A

  Draw a circle. Then divide it into five parts with 72 degrees each by a protractor. Even an elementary pupil can do this, but it might be hard to measure correctly 72 degrees by the protractor.
Method B

  Red segment EF shows the exact length of each pentagon's side. If the radius BC is 2cm. EF=√(√(1+2^2)-1)^2+2^2)=√(10-2√5) [cm]
You can draw a pentagon with a compas. You might get a more precise pentagon, but still looks complicated.

Metod C

  Inside the circle with a radius AB, draw two half-sized circles. Draw two circles with point F as the center point, so that they touch two half-sized circles. We can get the intersection points, J, K, L, and M. This looks simpler than method A and B.

4. Meaning of Gobousei and others

  I learned the method C for the first time at this time's research of pentagram. I also knew that how to draw pentagram was explained at the end of the volume six of Onmyoji(陰陽師)(Master of Yin yang). It is a 13-volume comic book written by Okano Reiko (岡野玲子)

陰陽師 6 (ジェッツコミックス)

• 出版社/メーカー: 白泉社
• 発売日: 2014/09/26
• メディア: Kindle版

  This picture looks mystical and beautiful, because it also has a yin-yang symbol in it. It is a cosmic dual forces symbol.

  Abeno Seimei, Onmyoji (magic master) in the Heian period in Japan used the crest of Gobousei(pentagram) as the symbol of Gogyo shiso (Five Elements Theory). But this is another story, maybe at another time.

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