The Orion constellation.

​The Orion constellation

by tonytran2015 (Melbourne, Australia).

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(Blog No.43).

#find North, #direction, #by stars, #Orion, #Sirius, #navigation, #constellation.

Celestial navigators who do not use declination and right ascension begin their navigation by learning the various bright, easily identifiable constellations in the sky (There are no more than 10 to learn.).

The Orion is usually chosen to be the first constellation to be learned. The Orion is a bright, easily identifiable constellation of December. It stays in the sky of December for the whole night, attains its highest elevation (or altitude) about midnight and is right on the Celestial equator.
It has the size of 30 degree (in angle) and has the shape of a waisted rectangle. Western sky watchers see a resembling to man in an armor vest and gave it the name Orion. Pacific sky watchers see its two brightest diagonal stars as the ends of a large stick in the sky.

It is never blinded by the Moon or any bright planet as the ecliptic is well away from it. As it is quite bright and has easily identifiable shape, it is usually used as the base (anchor marks) to start locating other stars.

1. The Orion on a Mercator sky-map.


Figure 1: The Orion constellation is right on the Celestial Equator and one third from the right edge of this Mercator sky-map.


The three dim stars in a straight line starting from the waist band and almost at right angle to it (not shown in this simplified Mercator sky map) are called the Dagger stars. The Dagger is at right angle to the Celestial equator and points along a great arc in the North to South direction on the Celestial sphere.

Rigel or Beta Orionis is bright star at the South leading corner of the waisted rectangle. Betelgeuse is bright star at the North trailing corner of the waisted rectangle. Bellatrix is a less bright star on the North leading corner of the rectangle.

Rotating the line Betelgeuse – Rigel by 90 degree in the anti-clockwise direction gives the line Betelgeuse – Aldebaran, (Aldebaran is also called alpha Tauri).

Extending the line Bellatrix-Aldebaran by another 50% makes it reaches Pleiades group of stars (not shown on this simplified Mercator sky map). This group has millions of stars fitting within an area as small as the area of the Moon (The area is equal to that of a fingernail on a fully extended arm). Most people can see a brush shape made of 7 brightest stars of this group.

On the trailing side of Orion lies the brightest star in the sky. It is Sirius. Rigel -Betelgeuse – Sirius form an almost equilateral triangle on the trailing side of the line Rigel – Betelgeuse.

Betelgeuse is the star of December 20th and the December solstice occurs on the 21st of December, on the following night .

The night when the brightest star Sirius attains its highest altitude at midnight is the first night of a new (Roman) calendar year (Is it a coincidence?).

2. Taking photos of the Orion.

Orion Constellation

Figure 2: Photo of the Orion Constellation taken with a Samsung Galaxy Note 2. The original photo has been digitally enhanced. Sirius is the brightest star on the lower half. Rigel, Betelgeuse and gamma-Gemini are in line (from bottom to top) and almost equally spaced.

Figure 3: Photo of the Orion Constellation taken with a Samsung Galaxy Note 2. The original photo has been digitally enhanced. On this night there was a bright object (planet ?) on the elliptic near to the leading shoulder of Orion.

The Orion is quite bright and photo can be taken using a smart phone such as a Samsung Galaxy Note 2 with no extra attachment.

Notes: The photos have been updated in March 2018.


[1]. tonytran2015, Finding North and time by stars in the tropics,, Finding North and time by stars in the tropics, posted on May 25, 2016

[2]. tonytran2015, Slide Sky-Map for displaying tropical stars,, Slide Sky-Map for displaying tropical stars., posted on October 7, 2016

[3]. tonytran2015, Finding North and time by stars,, Finding North and time by stars, posted on August 28, 2015


, posted on Circumpolar Stars Nth

The Scorpius constellation, posted on January 8, 2017


posted on October 21, 2016


Rice as emergency food, Using GPS in off-grid situations, Slide Sky-Disks with grid masks showing azimuths and altitudes, Slide Sky-Map for displaying tropical stars.…..all.

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8 thoughts on “The Orion constellation.

  1. I have been surfing online more than three hours today, yet I never found any interesting article like yours. It’s pretty worth enough for me. In my view, if all website owners and bloggers made good content as you did, the net will be a lot more useful than ever before.


    • For stars, It is easy on the Samsung Galaxy Note 2 as you can set the picture size and ISO number. The difficult part is not to let the autofocus jumping.

      With the shaddow on the Moon, it is beyond the theoretical resolution of that camera. All you would get is just a uniform white disk (I tried it) and you do need some attachment.

      Liked by 2 people

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