Finding North from unclear sky around September.

Finding North from unclear sky around September.

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. 168).

#find North, #finding North, #direction, #by stars, #Altair, #Fomalhaut, #September, #unclear sky,

Finding North from unclear sky around September.

Around September there are some bright stars shining the whole night. They include Deneb close to the Celestial North pole and Fomalhaut in the Southern sky. These 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 hous. 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 in Northern hemisphere.

Figure: Polar Inversion map for the Northern Celestial hemisphere. The map should be read with its September marking on its rim pointing towards the ground as illustrated here.
An observer has to align the polar map with marking for September on the rim (at 6 o’clock position) pointing downward. An observer in Northern latitude above 30 degrees will see the rotation of bright stars Vega, Deneb [1], Cassiopeia constellation, bright star Capella then Big Dipper constellations in that order.

Cassiopeia goes highest around 01am.

The bisector of the M shaped Cassiopeia goes through the Northern Celestial pole. The Northern Celestial pole is almost 30 degree below Cassiopeia.

Sky map Northern 3/4 sphere

Figure 2: Polar Inversion map of Northern Celestial 3/4 sphere.

3. Locating the Southern Celestial pole in Southern hemisphere.

Figure: Polar Inversion map for the Southern Celestial hemisphere. The map should be read with its September marking on its rim pointing towards the ground as illustrated here.

Sky map Southern 3/4 sphere

Figure: Polar Inversion map of Southern Celestial 3/4 sphere.

An observer has to align the polar map with marking for September on the rim pointing downward as illustrated here. An observer in Southern hemisphere or on the tropical zone would see Achernar [1] rising highest around 2am. Southern Celestial pole is the midpoint of Achernar and the two Pointers and is about 30 degree from Achernar.

 

4. Locating the Celestial poles from tropical stars.

A observer in the tropic should already know the two brightest stars Scorpius Antares (at the heart) and Scorpius Shaula (at the stinger end) of the Scorpius [1]. The straight line from Antares to Shaula goes through the bright star Fomalhaut which is of 60 degree distances from both Scorpius Shaula and Altair [1] which is a star of July and is close to the Celestial equator.

Figure 2: The Mercator map 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.

Figure: Fomalhaut and its nearby stars.

The bisector of the angle Shaula, Altair, Fomalhaut points to the Southern Celestial pole.

Southern Celestial pole is is of 90 degree distance from Altair and of equal 60 degree from both Scorpius Shaula and Fomalhaut.

5. Visibility of the stars.

Scorpius Altairs and Scorpius Shaula are stars of June that set close to midnight when viewed from tropical zone. Altair is a star of July that sets close to 02 am. Fomalhaut is visible for nearly the whole night in September.

References.

[1]. tonytran2015, Finding North from unclear sky in April, survivaltricks.wordpress.com, Finding North from unclear sky around July, posted on 2018, May 13.

[2]. tonytran2015, Finding North from unclear sky in April, survivaltricks.wordpress.com, Finding North from unclear sky around April, posted on 2018, April 12.

[3]. tonytran2015, Finding North from unclear sky around New Year, survivaltricks.wordpress.com, Finding North from unclear sky around New Year, posted on 2018, April 05.

[4]. tonytran2015, Finding North and time by stars, survivaltricks.wordpress.com, Finding North and time by stars, posted on August 28, 2015

[5]. , posted on

[6]. The Orion constellation., posted December 26, 2016

[7].The Scorpius constellation., posted January 8, 2017

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Blog image of Contents of Survival sub-page

These are the contents of SURVIVAL sub-page re-organized in book order for coherent reading.

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NAVIGATION (Celestial).

The Sun, the Moon and identifiable stars are used to work out North direction and time in this section.

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Finding accurate directions by a watch .. Posted on May 12, 2015.. This is my novel technique.

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Caution in finding North by bisector line of a horizontal watch. Posted on October 28, 2015: The commonly known “Scout method” using a horizontal watch may give directional errors of up to 180 degrees in some circumstances.

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Finding North and time by stars. Posted on August 28, 2015

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Sky map Southern 3/4 sphere

Finding North and time with unclear sky. Posted on October 17, 2015. This includes my novel method for finding North and with unclear sky.

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posted on October 21, 2016

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. Posted on May 25, 2016

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. Posted on April 05, 2018

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. Posted on April 12, 2018

. Posted on May 13, 2018

. Posted on September 16, 2018

Find North with Orion Equatorial stars

, posted November 3, 2016

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Slide Sky-Map for displaying tropical stars, posted on October 7, 2016

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, posted July 22, 2016

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Finding time to Sunset with bare hands. Posted on November 11, 2015 .This is my novel improvement for improved accuracy.

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Finding time to Sunrise with star maps, Posted on January 9, 2016 . This is a novel application for star-maps.

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Finding direction, distance and navigating to a distant base by stars (Part 1). Posted on January 27, 2016 . This is a novel application for direction of stars in the sky.

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Sky map Southern 3/4 sphere

Finding direction, distance and navigating to a distant base by stars, fine reading of latitude (Part 2).. Posted on February 6, 2016. This is a novel way of accurately arriving at any chosen destination latitude using no instrument.

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NAVIGATION using only constellations.

The Orion constellation., posted December 26, 2016

The Scorpius constellation, posted on January 8, 2017

The Southern Cross Pointer stars, posted February 26, 2018

NAVIGATION (Terrestrial).

Measuring angles and distances for outdoor survival, posted on June 29, 2016

DistPole

NAVIGATION (Instrumental).

Finding North with a lensatic compass, posted on August 21, 2017

Compass-Magnetic

Determining local magnetic declination by a magnetic compass, posted on March 31, 2016

Compass-Magnetic

, posted on June 14, 2016

compass Reversal

Selecting and using magnetic compasses, posted on July 9, 2016

Compass Lensatic Jap

Shadow stick navigation and graph of solar paths, posted August 19, 2016

ShadowStick

Using GPS in off-grid situations, posted December 06, 2016

Adding longitude and latitude lines to a map, posted August 23, 2017

Map w Coordinates

Navigating with an AM MW radio receiver, posted January 17, 2017

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Finding North direction and time using geological features, plants and animals, posted August 04, 2017

FIRE MAKING.

Making fire and lighting cigarettes with sunlight. Posted on February 27, 2016

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Quick fire making using sunlight, posted on January 4, 2017

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Mirror for making fire using sunlight., posted on April 13, 2016

20160105_143215C

Predicting-the-temperature-of-a-habitat, posted on August 31, 2017

compass thermometer

, posted October 23, 2018

Pushing away

FOOD

Rice as emergency food., posted December 24, 2016

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Dried-sweet-fruits-as-energy-food, posted December 24, 2017

Air-grown-mung-bean-sprouts-for-food, posted March 07, 2016

MISCELLANEOUS

Old maps:

Interesting maps of old Saigon , posted on March 20, 2016 .

SaigonThanhQuy

Detecting Counterfeit Currency

Detecting Counterfeit Currency, US dollars, posted on July 15, 2016

Hologram

, posted on November 15, 2016

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Cashless bartering

Cashless-bartering-for-survival, posted on February 20, 2017

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Other languages:

Survival-topics-available-in-other-languages , posted on june 18, 2017 .

click to go to polymeraust100dollarsMONEY , 20160105_145215CHOW TO , 20160105_145215CSOCIAL ISSUES , 20160105_145215CLIVING sub-pages

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Finding North from unclear sky around July.

Finding North from unclear sky around July.

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.130).

#find North, #finding North, #direction, #by stars, #Vega, #Deneb, #Altair, #July, #unclear sky

Around July there are some bright stars shining the whole night. They include Vega, Altair and Deneb. These three 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 hous. 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 in Northern hemisphere.

Figure: Polar Inversion map for the Northern Celestial hemisphere. The map should be read with its July marking (at 4 o’clock position) on its rim pointing towards the ground.
An observer has to align the polar map with marking for July on the rim (at 4 o’clock position) pointing downward. An observer in Northern latitude above 30 degrees will see the rotation of three bright stars Vega, Deneb, Capella then Big Dipper constellations in that order.

Vega and Deneb go highest around 24 hr.

The bisector of the line Vega Deneb goes through the Northern Celestial pole. The pole is almost of equal distances of 45 degrees from each of them.

3. Locating the Southern Celestial pole in Southern hemisphere.

Figure: Polar Inversion map for the Northern Celestial hemisphere. The map should be read with its July marking (at 8 o’clock position) on its rim pointing towards the ground.
An observer has to align the polar map with marking for July on the rim (at 8 o’clock position) pointing downward. An observer in Southern hemisphere or on the tropical zone would see the Southern Cross Pointers highest around 18 hr, then Antares around 20 hr. Achernar is seen rising before Sunrise. The midpoint between the Pointers and Achernar is almost the Southern Celestial pole.

4. Locating the Celestial poles from tropical stars.

A observer in the tropic should already know the very bright star Bootes and the bright star Antares in the Scorpius constellation used in April.

Figure 1: Photograph of Spica (near the bottom edge), Bootes Arcturus (near the right edge) and Antares (1/8 of the width from the left edge) forming a triangle. Celestial North is at 01 o’clock position (30 degree clockwise from vertical) in this photo. There is a very bright planet (1/2 from left edge, 1/3 from bottom) traveling on the Ecliptic in this photo.

Figure 2: The Mercator map 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.

On the trailing side of Bootes Arcturus and Antares, (click the above Mercator map for details) there is a bright star of equal distances of 60 degrees to both of them. This star is Altair, which is as bright as Antares.

Following the line Antares to Bootes Arcturus, turning anti-clockwise by 90 degrees at Bootes Arcturus and traveling for 60 degrees takes us to Vega, which is as bright as Bootes Arcturus. The line (Antares, Arcturus) is nearly at right angle to the almost straight line (Spica, Arcturus, Vega).

The line (Bootes Arcturus, Antares) is nearly parallel to the line (Vega, Altair) which lie slightly nearer to Bootes Arcturus.

Vega is as bright as Bootes Arcturus while Altair is as bright as Antares.

Sky map Northern 3/4 sphere

Figure 3: Polar Inversion map of Northern Celestial 3/4 sphere. The line (Vega, Altair) is 30 degrees long and is nearly parallel to the line (Bootes Arcturus, Antares) which is 60 degrees long.

Rotate the line (Altair, Vega) about Altair by 10 degrees counter-clockwise give the great circle through the two Celestial poles. Northern Celestial pole is nearer to Vega and is 80 degrees from Altair. Southern Celestial pole is nearer to Altair and is 100 degrees from Altair.

Trailing 2 hour behind Vega is the bright star Deneb (see the Mercator star-map). (Vega, Altair, Deneb) is known as the Summer Triangle. The bisector of the angle Vega, Altair, Deneb points to the Northern Celestial pole.

Bright Stars 20 Plus 2

Figure 4: Table of 20 brightest +2 stars in order of appearance.

5. Visibility of the stars.

Altair is visible for nearly the whole night in July. The Summer Triangle is visible for nearly the whole night in July. Click on the Mercator map for details.

6. CAUTION with planets
The Moon and planets travel on the Ecliptic. Observers should take care not to mistake any planet for Antares in the Scorpius constellation.
A planet is always brighter than any star, including Sirius, moves from night to night, and does not twinkle in clear sky.

References.

[1]. tonytran2015, Finding North from unclear sky in April, survivaltricks.wordpress.com, Finding North from unclear sky around April, posted on 2018, April 12.

[2]. tonytran2015, Finding North from unclear sky around New Year, survivaltricks.wordpress.com, Finding North from unclear sky around New Year, posted on 2018, April 05.

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

[4]. , posted on

[5]. The Orion constellation., posted December 26, 2016

[6].The Scorpius constellation., posted January 8, 2017

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Finding North from unclear sky around April.

Finding North from unclear sky around April.

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.124).

#find North, #finding North, #direction, #by stars, #Spica, #Bootes Arcturus, #Antares, #April, #unclear sky
Around April there are some bright stars shining the whole night. They include Spica, Bootes Arcturus and Antares. These three 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 hous. 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 in Northern hemisphere.

Figure 1: Stars in the Northern hemisphere rotates anticlockwise around the North pole.

An observer in Northern latitude above 30 degrees will see the rotation of three bright stars Vega, Deneb, Capella then Big Dipper constellations in that order.

Big Dipper constellation goes highest around 22 hr.

3. Locating the Southern Celestial pole in Southern hemisphere.

Figure 1: Stars in the sothern hemisphere rotates anticlockwise around the North pole.

An observer in Southern hemisphere or on the tropical zone would see the Southern Cross Pointers for the whole night.

4. Locating the Celestial poles from tropical stars.

Figure 1: The Mercator map 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.

An Earth bound observer in Southern hemisphere or on the tropical zone can identify the forward swept broom (or a duck foot (?), a bird foot (?) or a tree with 3 upper branches (?)). formed by the brightest star Sirius and four surrounding bright stars Canopus, Orion-Rigel, Betelgeuse and Procyon. The line Canopus to Sirius make the 35 degrees long broomstick handle and three lines from Sirius to each of the other three stars form three branches of the forward swept broom head (see the star maps). Sirius to Procyon is the trailing branch of the (three branched) broom head.
Doubling the travel from Sirius to Procyon takes us to another bright star named Pollux.

Two thirds of the line from Procyon to Pollux is a point on the Ecliptic (the great circle containing the.Sun and all planets). Turning anticlockwise 100 degrees at this point and traveling by a distance of 40 degrees takes us to a less bright star Leo Regulus. Keeping the direction from that two thirds point to Leo Regulus and travel for another 50 degrees takes us to a brighter star Spica. Spica is 90 degree in distance from the that two thirds point. (Observers from the Southern Hemisphere may also see that the great circle arc going through the long axis of the Southern Cross goes by 50 degrees to get very close to Spica. Draw the line from Southern Cross to Spica and then turns 30 degrees anticlockwise and continue for another 30 degrees to reach Bootes Arcturus.)

Turning clockwise by 90 degrees at Spica to leave the Ecliptic and traveling by 30 degrees takes us to a much brighter unmistakable star Bootes Arcturus.

Instead of turning right toward Bootes Arcturus, traveling along the Ecliptic for another 50 degrees take us to a bright star Antares in the Scorpius (Observers from the Southern Hemisphere may also see that Antares is 45 degrees clockwise and 45 degrees distance from the direction of dim Pointer to bright Pointer.).

Figure: Antares is the bright star in the Scorpius constellation which has the shape of a declawed scorpion. Two bright objects on the third top of the photo are planets traveling on the Ecliptic. Northern Celestial pole is from the top left (11 o’clock) direction of the photo.

The stars Spica, Bootes Arcturus, Antares form an arrow-head pointing North.

The midpoint of the great circle arc from Spica to Bootes Arcturus is almost on the Celestial equator. Rotating this arc clockwise by 30 degrees makes its extension goes through both Celestial poles. Northern Celestial pole is 90 degrees from the midpoint and on the side of Bootes Arcturus. Southern Celestial pole is 90 degrees from the midpoint and on the side of Spica.

The internal bisector of the angle formed by (Spica, Bootes Arcturus, Antares) points to the Southern Celestial pole while its rearward extension points to the Northern Celestial pole.

Figure: Photograph of Spica (near the bottom edge), Bootes Arcturus (near the right edge) and Antares (1/8 of the width from the left edge) forming a triangle. Celestial North is at 01 o’clock position (30 degree clockwise from vertical) in this photo. There is a very bright planet (1/2 from left edge, 1/3 from bottom) traveling on the Ecliptic in this photo.

Bright Stars 20 Plus 2

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

5. Visibility of the stars.
Orion constellation, Sirius and its surrounding stars are visible after Sunset. Spica, Bootes Arcturus and Antares are all visible for nearly the whole night in April.

Figure 1: Azimuth and elevation angles of stars for equatorial observers.

Figure 2: Azimuth and elevation angles of stars for observers on 30 degrees North latitude.

Figure 3: Azimuth and elevation angles of stars for observers on 30 degrees South latitude.

6. CAUTION with planets
The Moon and planets travel on the Ecliptic. Observers should take care not to mistake any planet for a navigational bright star.
A planet is always brighter than any star, including Sirius, moves from night to night, and does not twinkle in clear sky.

References.

[1]. tonytran2015, Finding North from unclear sky around New Year, survivaltricks.wordpress.com, Finding North from unclear sky around New Year, posted on 2018, April 05.

[2]. tonytran2015, Finding North and time by stars, survivaltricks.wordpress.com, Finding North and time by stars, posted on August 28, 2015

[3]. , posted on

[4]. The Orion constellation., posted December 26, 2016

[5].The Scorpius constellation., posted January 8, 2017

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Caution in finding North by bisector line of a horizontal watch. Posted on October 28, 2015

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Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015

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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.

RELATED SURVIVAL BLOGS (Added in December 2016)

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Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015

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Finding North direction and time using the Moon surface features. Posted on July 1, 2015.

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Finding North and time by stars. Posted on August 28, 2015 .

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Finding North and time with unclear sky. Posted on October 17, 2015.

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Click here for my other blogs on divider43.jpgSURVIVAL

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Finding accurate direction by a watch

Method for finding accurate directions by a common analogue watch.

by tonytran2015 (Melbourne, Australia).

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(Blog No.120).

WatchCompass_22NL

#find North, #finding North, #compass, #direction, #by Sun, #bisector, #using watch, #with watch, #tilted watch, #inclined watch, #navigation, #without compass

This method uses a common 12-hour watch with analogue face for finding directions. Unlike the traditional method of using the hour hand of a flat lying watch, my method uses a watch tilted from the vertical and gives better accuracy for both North and South hemispheres including tropical zones. When applied to the arctic and antarctic regions, the watch is tilted by more than 67 degrees and lies almost flat on the ground; it becomes the traditional method using flat lying watch.
This method use the position of the Sun, time and known latitude angle to determine directions and Sun declination (therefore estimation of current month of the year).
The method for Northern latitudes is described below.

Method for Northern latitudes.

DirectionBySun_12N

The red line is the bisector. The line CB is drawn on a card representing the half-plane to enable accurate alignment to the Sun

WatchCompass_22NL

The bisector is in the opposite direction of a corresponding 24 hr hand on a 24 hr dial

watchcompassJ

Figure: Summary of finding North by a watch. Red hand is the bisector of 0 hr direction and the hour hand; green hand is its reflection across the (6-12) axis. Axis C-BN for Northern hemisphere is parallel to red hand at equinox days and is (raised above)/(dipped below) the watch dial by 23 degrees at local summer/winter solstice. Axis C-BS for Southern hemisphere is parallel to green hand at equinox days and is (raised above)/(dipped below) the watch dial by 23 degrees at local summer/winter solstice. Green drawing marks are for Southern hemisphere and are the mirror reflection of red drawing marks.

Method for Southern latitudes.

Red hand is the bisector of 0 hr direction and the hour hand; green hand is the reflection of red hand across the (6-12) axis.

In the southern hemisphere points the green hand instead of the red hand.
No ambiguity in equatorial latitudes.
The watch is placed almost vertically in equatorial latitudes by both methods. Methods for both Northern and Southern latitudes gives exactly the same outcomes.

Extension application for both hemispheres.

Figure: Summary of finding North by a watch.

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find North by the Sun

Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015

Finding North direction and time accurately from the horn line of the Moon. Posted on August 12, 2015. This is my novel technique.

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Finding North direction and time using the Moon surface features. Posted on July 1, 2015.

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, posted on Circumpolar Stars Nth

Finding North and time by stars. Posted on August 28, 2015

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, posted July 22, 2016

NorthByKnownStar

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Identifying moderately bright navigational stars.

Identifying moderately bright navigational stars

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. 27).

#find north, #navigation, #survival, #moderate stars, #bright star, #Antares, #Fomalhaut, #direction, #distance, #great circle, #navigation, #stars, #neighbour stars, #sky map

Introduction.

Some navigational stars are only moderately bright although they are in the top 20 brightest stars. Antares and Fomalhaut are two such stars. They are used for navigation from September to November but are not easy to identify among their nearly as bright neighbours. The method for identifying them is to relate them to brighter neighbours which have been identified in previous periods of the year.
(GPS navigation cannot be relied on during periods of uncertainty. Traditional methods of navigation is still a necessary skill.)

Using an identifying map.
Knowing the date or even only the month of a star help locating parts of the sky where it may be found. The map giving distances and angles to its more distinctive neighbours then help its identification.

The maps are to be held such that its shown Celestial pole is pointing close to that actual Celestial pole whether it is in the sky or below the ground. The map is thus to be held in the star direction but oriented either upright or up-side-down.

Examples:

Figure 1: Antares in Scorpii with its neighbours. The centering mark is the Southern Celestial pole.

Figure 2: Fomalhaut with Alpha, Beta Grus and their neighbours. The centering mark is the Southern Celestial pole.

ariessmallc30.jpg

Figure 3: Hamal in Aries and its brighter neighbours. The tail of the inverted Little Dipper in the North is the North pole.

The first two maps make easy the confusing identification process of these two Southern navigational stars for October.

The third map makes easy the identification process of the dim Northern star Hamal in Aries for November.

References.

[1]. 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

[2]. tonytran2015, Finding North 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.

RELEVANT SURVIVAL blogs (Added after February, 2017)

, posted on May 06, 2015 .

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find North by the Sun

Finding accurate directions using a watch, posted on May 19, 2015

Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 2015

Finding North direction and time accurately from the horn line of the Moon. Posted on August 12, 2015. This is my novel technique.

wpid-wp-1439376905855.jpeg

Finding North direction and time using the Moon surface features. Posted on July 1, 2015.

wpid-wp-1435755781395.jpeg

Finding North and time by stars. Posted on August 28, 2015

Finding North and time with unclear sky. Posted on October 17, 2015.

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, posted July 22, 2016

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Slide Sky-Map for displaying tropical stars.

Slide Sky-Map for displaying tropical stars

by tonytran2015 (Melbourne, Australia).

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

#find North, #finding North, #direction, #time, #by stars, #Mercator, #sky map, #star map, #slide sky map, #navigation, #tropic, #declination, #right ascension.

slide sky map

Figure 1: Illustration of the Slide Sky-Map using the mask for 15 degree North latitude.
Slide Sky-Map for displaying tropical stars (blog No. 26).

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It is an advantage to know the arrangement of stars for the nights before engaging in nightly activities such as going to the country side or navigating your way by stars. It is difficult to have a good display of the tropical night sky with current commercially available circular star maps as they have a lot of distortion for tropical visualization whereas easy visualization requires that groups of stars should appears with the same shape as actually observed in the sky and the constant altitude curve should be nearly circular around the zenith point.

The device given in this posting gives the desired displays with low distortion for the tropical night sky and has been designed for use with latitudes between the two tropical lines. I give it the name Slide Sky-Map (which is similar to the name Slide Rules of similar looking mathematical devices before the age of calculators).

It is made of Mercator map of stars and of the viewing grids to give elevation and azimuth angles of stars to observers located near to 0 degree, 15 degree North and 15 degree South in latitude.

It will be useful to tropical people who want to learn the stars by themselves or need to refresh their nightly knowledge of the sky before going out. It is inexpensive, light weight, small, flexible, durable and quite portable. If made from waterproof materials, it may also be used as a low cost standby star map for travelers, hikers and seamen traveling in the tropic (my is made from waterproof sheets).

The device is made by following instructions in the next 4 steps. PLEASE READ THROUGH ALL STEPS BEFORE STARTING ANY CONSTRUCTION.

1. Making the maps for the core.

mercatorx1p6

Figures 1a: The Mercator map for the front of the core of the Slide Sky-Map.
star map mercatorx1p6

Figures 1b: An alternative Mercator map with star names for the front of the core of the Slide Sky-Map

mercator8fx1.6polarc30.jpg

Figures 2: The map on the reverse side of the core.

The map on the front of the core of the slide sky-map is a Mercator map with continuation by its repeat copy. The map here wraps around the Celestial equator by 600 degrees, meaning that it has about 1.7 times the width of the minimal Mercator map. The extra length allows the slider covering 180 degree in the East-West direction to be centered on any given longitude.

The two inversion maps of the North and South polar regions of the Celestial sphere are overlaid at the two ends of the same Mercator map and the combined map is placed on the reverse side of the core. The two insets represent the two polar regions of the Celestial sphere not displayed on the Mercator map. They help visualizing the two polar zones of the Celestial sphere, they can be easily joined to the polar sides of the Mercator map using shared common constellations present in both types of maps as stitching guides.

The core maps are to be printed on both sides of a thick sheet of A4 waterproof paper. This thick sheet of paper forms the core fitting inside the sleeves of next few steps. Alternatively the core maps can be printed on waterproof A4 papers and glued onto the opposite sides of a piece of thick waterproof board used as the core.

 

2. Making azimuth and elevation masks for the slider

mercator grid 00deg mask

Figure 1: The grid mask for 0 degree latitude.

mercator grid15d N.jpg

Figure 2: The grid mask 15 degree North latitude.

mercator grid 15d S.jpg

Figure 3: The grid masks for 15 degree South latitude.

A grid mask is placed on top of the core map to read the azimuth and the elevation of the stars drawn on the map. An observer must use the mask drawn for his latitude.

Description:
The smallest circle of each grid is graduated into 12 intervals of 30 degrees each to show the azimuth angle of the star or direction from True North. The curves radiating from the center represent the great circles from the zenith to the terrestrial points of 0 degree (North), 30, 60, 90 degree (East) , 120, 150, 180 degree (South), 210, 240, 270 degree (West), 300, 330. The concentric nearly circular curves represent the constant elevation circles in the sky. They are placed at 30, 60 and 90 degrees from the zenith. The curve at 90 degrees from the zenith represents the horizon on flat locations. The graduation can also be read from the horizon circle toward the center to show the elevation angle of the star. The position of any star in the sky can be read against the grid.

There are 3 grid masks given for this design. Select one that is based on a latitude nearest to your current latitude.

For latitude between 8 degree North and 8 degree South select the mask based on 0 degree latitude.

For latitude between 7 degree North and 23 degree North select the mask based on 15 degree latitude North.

For latitude between 7 degree South and 23 degree South select the mask based on 15 degree latitude South.

You can make all three masks as each can be easily fit into and removed from the device as you move to a location with a different latitude.

Make each mask with the CORRECT size and print it at the CENTER of an uncut A4 transparent sheet. Print the selected grid on a waterproof transparent film by a photocopier. If this cannot be done you may have to print the mask on an ordinary piece of paper, place a transparent film on top of it and trace the grid lines onto the waterproof transparent film using a pen with waterproof ink.

3. Making the slider (improved design, 2017, August 31).

slideskymap00

Figure 1: Photograph of an actual Slide Sky-Map fitted with the mask for the equator.

BrightStars20Plus2

Figure 2: Table of bright stars for the back side of the double layered slider sleeve.

Figure : The Mercator map of the sky for inhabitants of Tropical Zone. North direction is on its top. 24hr of R.A. is near the right side and R.A. increases towards the left (East) of the map.

The slider consists of a double layer white sleeve fitted with a transparent rectangular strip carried between its front layers.

Wrap a waterproof, white, thick sheet around the rectangular core map to make a white sleeve of no less than 360 degree along the East West direction of the core map (that is wrapping no less than two third of the length of the core map). The core should fit snugly inside the white sleeve and should be able to slide smoothly along its East West direction inside the white sleeve.

Cut a rectangular window on the front center of this white sleeve to reveal 180 degree width of the core map. The back of this white sleeve should be glued or taped to make it a proper sleeve.

Wrap another layer of the same waterproof, white material around the inner sleeve just made to make a white outer sleeve that fits snugly on the inner sleeve. The sleeve has now two layers.

Make sure that there is SUFFICIENT GAP between the two sleeves so that the core map can also be inserted into and can also slide in the GAP between the two front layers of the double layered slider.

Make the two layers stick together on their back sides by tapes or glue. Then cut the window through the outer layer so that the core map can be observed through the front window as if the slider sleeve was made of only a single layer.

Figure: The sleeve has two layers.

You may like to add the table of bright stars (Fig. 3) to the (uncut) back side of the double layered white sleeve to facilitate calling star names.

Choose the transparent sheet with the printed mask for your latitude. Cut it into a rectangular shape with 2 long arms extending from the East and West sides of the transparent grid mask. The rectangular transparent sheet has its width slightly wider than the width of the core map.

Insert the rectangular transparent sheet BETWEEN the two FRONT LAYERS of the double layered slider sleeve. Align the printed window of the transparent sheet to the cut window of the double layered sleeve. The East-West arms of the mask should be trimmed so that they only protrude slightly out of the double layered sleeve just enough to make easy insertion and removal of the mask.

In this way, any of the transparent mask can be fitted into or removed from the double layered sleeve whenever the user requires a new mask for his new latitude.

4. Final assemblage.

slideskymap15s

Figure 1: Front view of a Slide Sky-Map fitted with the mask for 15 degree South latitude.

slideskymap2backc100.jpg

Figure 2: Back view of a Slide Sky-Map.
Slip the core map into the inside of the double layered sleeve. The core map is now behind the transparent grid mask.

5. Usage.

The sky at night is represented by the core map going toward its west under the transparent window (that is it goes from left to right under the viewing window).

1/- Check that the center cross of the grid is on the declination line corresponding to your required latitude.

2/- The four vertical lines for equinoxes and solstices are printed on the core map. Other date lines are interpolated from them.

Place the center of the sliding window on the current date to see the mid-night sky for the date.

3/- Then slide the core map by half a division (15 degree on the equator or half a month) to the east or to the west for every hour ahead of or after midnight.

4/- The latitude for the grid not being exactly that of the observer and the true time at the location is not being equal to the zonal time causes the stars inside the smallest circle around the zenith to have slightly inaccurate position relative to the grid. However the lines joining these stars still give accurate directions and the stars still help identifying other stars near the horizon. The stars near the horizon have their values of azimuth and elevation angles given more accurately by the Slide Sky Map.

6. Record of a previous design.

(For reference only, do not use this obsolete design).

The slider consists of a white inner sleeve and a transparent outer sleeve tightly fit together.

Wrap a waterproof, white, thick sheet around the core (printed with maps) to make a white sleeve of no less than 360 degree along its East West direction (that is wrapping no less than two third of the length of the core map). The core should fit snugly inside the white sleeve and should be able to slide smoothly along its East West direction inside the white sleeve.

Cut a rectangular window on the front center of this white sleeve to reveal 180 degree width of the core map. You may like to add the table of bright stars (Fig. 3) to the (uncut) back side of the white sleeve to facilitate calling star names.

Choose the transparent sheet with the printed mask for your latitude. Cut it into the shape of a cross with 4 long arms extending from 4 sides of the transparent grid rectangle window. Each arm has its width equal to the size of the corresponding side of the adjoining window. Its North and South arms will be joined together to make a second, transparent sleeve fitting tightly outside the white sleeve, its long East and West arms will be slipped into the inside of the white, inner sleeve to anchor it on the white, inner sleeve. The East-West arms should protrude slightly out of the inner sleeve to make easy insertion of the sliding core into the white sleeve.

Wrap the transparent sheet tightly outside the inner sleeve and tape its North and South arms together to form a transparent sleeve with its grid right on the cut window of the inner sleeve. The East and West arms of the transparent sheet are slipped into the inside of the inner sleeve to lie along the East West direction underneath the white layer to anchor the transparent sheet on the white, inner sleeve.

In this way, any of the transparent outer sleeve can be fit into or removed from the inner sleeve whenever the user requires a new mask for his new latitude.

Slip the core map into the inside of the cardboard sleeve. Make sure that it goes behind the two transparent arms inside the sleeve so that it can travel fully from East to West.

Reference.

[1]. 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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Navigating with an AM MW radio receiver, posted January 17, 2017, The Scorpius constellation, posted January 8, 2017, The Orion constellation., posted December 26, 2016, Rice as emergency food., Using GPS in off-grid situations, Shadow Stick Navigation, posted on 19 Aug 2016

, posted on

Circumpolar Stars Nth

. Posted on May 25, 2016

star map Mercator

Slide Sky-Disks with grid masks showing azimuths and altitudes, posted on 03 Nov 2016 ,

, posted July 22, 2016DirectionTimeByStars

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Shadow stick navigation and graph of Solar paths

Shadow stick navigation and graph of Solar paths

by tonytran2015 (Melbourne, Australia).

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

#find North, #finding North, #direction, #time, #shadow stick, #Sun shadow, #Solar declination, #graph, #Solar path,

Shadow stick navigation and graph of Solar paths.

In the 1950’s some maps have their graphs of Solar paths printed next to the compass roses. A graph of Solar paths helps the users of that map (for some certain small area) in orientating it correctly using only the direction of the Sun and the approximate time (month) in the year. It also help people visualize the direction of the Sun at each time of the year relative to a building. For some unknown reasons, graphs of Solar paths are all replaced by compass roses in modern maps. The roses take up nearly the same areas while give less information,.

A graph of Solar paths can also be used on its own with a vertical stick in the center to tell (local) time and direction. This application is suitable to day time navigation of vehicles as it relies only on the Sun and needs no battery. The application devices can be left on the vehicles as they are of very low-cost and are burglary resistant.

This posting shows how to construct and use a graph of Solar paths for your own map or for use on its own.

1. Description of the basic graph of Solar paths.

Solargraph10N

Figure: A typical graph of Solar path. This particular graph is made for 10 degrees North, for an example use in Saigon (around Tan Son Nhat International Airport).

The graph of Solar paths is a circular disc with concentric circles and radial lines bearing division marks to represent the elevation and azimuth angles of the Sun at different times of principal days.

The perimeter circle of the graph is graduated into 360 degrees to show the azimuth angle of the Sun from True North. It can also be used as a protractor for measuring angles. The concentric circles are the constant elevation circles.The radial lines are graduated 0 to 90 to show the angle from zenith to the Sun. The circle 90 degrees from the zenith represents the horizon in flat locations. The graduation can also be read from the horizon circle toward the center to show the elevation angle of the Sun.

All positions of the Sun at various time on an equinox day are plotted to make a Solar path for that day. The paths for the Sun on two solstice days are similarly plotted. The time for the each Solar position on a path is also given by time marks such as 6hr, 12hr and 18hr.

It is assumed here that the Sun attains its highest elevation at noon of local time everyday (the duration of the day is therefore slightly longer or shorter than 24hr, to discount any effect from the Equation of time).

2. Using a graph of Solar paths.

Be certain that the graph is for your current latitude! If it is printed on a map, it is for the latitude of that area.

The following steps show how to use the graph on an equinox day:

1/- Point your index to the Sun.

2/- Point your middle finger horizontally.

3/- Hold still the two fingers and measure the angle between them by placing those fingers along two radial lines of the Graph of Solar paths. Read the value of the angle. It is called the elevation angle of the Sun.

4/- Follow the Solar path for that day on the graph to its 2 points having that elevation value. The two intersection points give two times (one before and one after noon) and two positions of the Sun.

5/- Choose the one of those two points fitting your half day (either before or after noon-time).

6/- Lay the graph of Solar path horizontally. Rotate the graph until the line from the graph center to the chosen intersection point goes beneath the Sun.

7- The 0 degree azimuth line of the graph is now aligned along the direction of the true terrestrial North.

For any other day of the year, use the particular path for it. A graph supplies at least three paths: for summer solstice day (21 June for Northern Hemisphere), for equinox days (21 March and 23 September), and for winter solstice day (21 December for Northern Hemisphere). The path for any other day can be interpolated from these three.

3. Interpolation for any arbitrary day of the year.

wpid-divider10l.jpg

Figure: Solar declination for various days of the year.

The declination value for any day varies between the principal values for solstice and equinox days and its solar path varies similarly.

The rough graph here allows the estimation of how close the Solar path of any day is to its two neighbouring bounds for the equinox and solstice days.

4. Making a graph of Solar path for your latitude.

SunCelestSphere

Figure: The Celestial sphere directly above a circular disc of the same diameter.

The following steps show how to make your own graph of Solar paths for your arbitrarily chosen latitude.

1/-Draw 9 equidistant concentric circles and 12 (or 36) equally spaced radial lines as the frame for the planar polar coordinate system.

2/- Place this disc (as the frame) on a horizontal plane.

3/-Set the angle between 2 divider legs to be 90 degrees.

4/-Place the hinge of the divider exactly above the center of the disc. It should be at the center of the sphere in the figure.

5/- Hold the first leg of the divider pointing downward, inclined by latitude angle, in the 180 degree or 360 degree direction depending on your Lower Celestial pole being South or North Celestial pole. The first leg point downwards along the Celestial axis in the figure.

6/- The second leg will point at different directions to the Sun for different times of the day when the divider is rotated about the first leg. It uppermost position corresponds to mid-day.

7/- Looking downwards along the first leg of the divider gives the picture of a 24 hour clock with the second leg being the hour hand. The clock dial is clockwise when you are in Northern hemisphere and anticlockwise when Southern.

8a/- Looking at the second leg from the top of the disc gives azimuth angle of the Sun.

8b/- Looking at the second leg from its side gives elevation angle of the Sun.

9/- Record on the polar graph on the disc the direction of the second leg for 6hr, 12hr and 18hr.

10/- Join the curve by a smooth curve. (Additional points may be added for a more precise curve).

11/- The curve is the Solar path for equinox days.

12/- Set the angle between the divider legs to 90+23.5 degrees and repeat steps 4 to 10 to draw Solar path for summer solstice day.

13/- Set the angle between the divider legs to 90-23.5 degrees and repeat steps 4 to 10 to draw Solar path for winter solstice day.

The graph of Solar paths is now COMPLETE. It is usable with only 3 paths for equinox and solstice days. Paths for other days can be interpolated from them.

Manually drawn graphs are accurate enough for normal usage. If all steps are simulated with your computer, the graph will be very accurate.

If you live near to 20 degrees N latitude (20 degrees is only an example value) and need a graph for your personal use but don’t want to spend time drawing it, you can do a Google search for “graph solar path 20 degrees”. The search results will give many ready made graphs and you can select one of them for your own use.

5. Application 1: Shadow stick navigation for vehicles.

ShadowStick

Picture of Application 1: Shadow stick navigation for vehicles.

You can print your graph on a disc for use in your vehicle. You can use only one single disc if the vehicle does not travel more than 5 degrees = 300 nautical miles = 555km in latitude from your base.

Lay the rotatable disc horizontally with a vertical stick at its center. When the shadow of the stick is on the opposite side of the chosen point on the graph, the line of 0 degree points exactly at True North. This method of Solar navigation only needs the graph and a vertical stick and is immune to vehicle shocks and stray magnetism.

This method needs the above device and is less general than my other methods given in references [1, 2, 3] but may be easier for users to comprehend.

6. Application 2: As a North direction marker

DirectionMarker

Picture of Application 2: As a North direction marker

Figure: Map of an old citadel overlaid on a modern satellite based map. The graph of Solar paths is given on bottom left corner instead of the compass rose.

The illustration is the map of an old citadel overlaid on a modern satellite based map. The graph of Solar paths is given on bottom left corner instead of the compass rose. The graph of Solar paths gives more useful information than a compass rose occupying same area.

Notes on my composite map: The modern map data are used under Open License from Open Street Map, the data are owned by Open Street Map Contributors. The old area has adjusted and selected data from a 150 year old map with expired Copyright.

7. Additional observations.

The graph of step 1 shows that the Sun can travel on the other side of your zenith when you are in a tropical zone. This explains why the bisector method using a horizontal watch may give you an error of 180 degrees around summer solstice (see reference [2]).

The graph shows that the terrestrial direction (azimuth) angle of the Sun varies quickly with time when the Sun is close to the zenith point. This quick change in direction may be main the reason for the ancient custom of cross-country travelers to take their rest when the Sun is near to their zenith.

You can also use a graph for your EXACT latitude to calculate if and for how long a proposed neighbouring tall building may over-shadow your house. Architects have been using graph of Solar paths and physical sunlight simulator on their scale models even before 1914.

References.

[1]. tonytran2015, Finding directions and time using the Sun and a divider, survivaltricks.wordpress.com, https://survivaltricks.wordpress.com/2015/05/06/finding-directions-and-time-using-the-sun-and-a-dividing-compass/, posted on May 6, 2015.

find North by the Sun

[2]. tonytran2015, Finding accurate directions using a watch, survivaltricks.wordpress.com, https://survivaltricks.wordpress.com/2015/05/19/finding-accurate-directions-using-a-watch/, posted May 19, 2015

[3]. tonytran2015, Caution in finding North by bisector line of a horizontal watch, survivaltricks.wordpress.com, https://survivaltricks.wordpress.com/2015/10/28/caution-in-finding-north-by-bisector-line-of-a-horizontal-watch/, Posted on October 28, 2015.

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image

, posted on

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Finding North direction and time by any bright star.

NorthByKnownStar

Finding North direction and time by any bright star

by tonytran2015 (Melbourne, Australia).

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#find North, #find, #direction, #time, #bright star, #Sun, #divider, #navigation.

Find North Direction and time by any bright star.

Most people living in the Northern temperate and arctic zones know how to find the star Polaris to find North direction and can even tell time by the orientation of the Little Dipper (part of the Little Bear). But Polaris is not an easily seen bright star and may even be hidden from view for people in Tropical zone and in Southern Hemisphere.

This posting shows how to use ANY arbitrarily known star to find North direction and time, and is useful to non-users of Polaris star. The method is similar to that given previously using the Sun [1] and is useful when only one bright star is visible in an unclear sky (affected by thick clouds or pollution).

The divider compass in this posting is only for instructional purpose and is not needed in actual application. The user may use any two of his fingers instead.

1. Requirements by the method.

To apply this method you need:
1. Your current latitude,

2. The current date in the Solar Year,

3. An unmistable bright star,

4. Its Declination and its Right Ascention already converted to Date of that Star in the Solar Year (see the details on the Conversion in the following section).

2. The date of a star.

BrightStars20Plus2

Figure: Table of bright stars with their approximate dates .

The date of a star should be known, even only approximately by the month, if the user wants to tell time from that star.

The date is obtained from the linear conversion:

a. 00:00 hr of R.A. —-> Sep 23 in Date

b. 06:00 hr of R.A. —-> Dec 21 in Date

c. 12:00 hr of R.A. —-> Mar 21 in Date

d. 18:00 hr of R.A. —-> Jun 21 in Date
Any star is visible nightly (either from Sunset to its setting or from its rising to Sunrise) for more than 9 months each year. The visibility cycle for each star begins with the star seen rising near the Eastern horizon few minutes before Sunrise. On subsequent days, the star rises earlier and earlier, it travels gradually towards the West and remains for longer and longer duration in the night sky until one day it stays for the whole night. The star is therefore called a star of that date. After that day, the star is seen setting in the West in the night. On subsequent days, its lead on the Sun gradually increases and it sets on the West at earlier and earlier time. Near the end of the cycle, the star is visible above the Western horizon for only few minutes after Sunset. It then sets on the West. At the end of this cycle, the star is too close to the Sun to be visible in the sky. The cycle then repeats from the beginning.

Example:

Boote Arcturus is a star of April 25th with declination 19 degree N. Step 6 of reference [2] shows how to easily identify it.

It reaches its highest elevation at mid-night of that date and remain visible for that whole night.

In February it rises about 4 hr after Sunset and has not enough time to complete the journey to the West. On April 25th it rises at about Sunset to complete the journey to the West about Sunrise. In June it is seen already high in the sky at Sunset and set on the West 4 hr before Sunrise.

3. Selecting a star for current month in the year.

PolrNorthNC20const8

Figure: Sky map (Inversion type) of the Northern Celestial 3/4-sphere showing only 20 brightest stars and some constellations.

polrsouthq3c60.jpg

Figure: Sky map (Inversion type) of the Northern Celestial 3/4-sphere showing only 20 brightest stars and some constellations.

Select a bright star of a date in the year near to your current date (or month) and read its declination from any source such as the internet, your own tables or the two star maps supplied here. If you use the star maps, its declination is read from the constant declination circles and its date from the rim on the opposite side (that is also the point closest to the Sun on the elliptic circle).

This method requires POSITIVE IDENTIFICATION of your chosen star. To positively identify it, you may need to see

1/- either neighbouring bright stars, their relative distances and orientation

2/- or surrounding dimmer stars making up the constellation containing it.

When that star is the only visible one in the sky you may have to identify it relying on its appearance details in previous nights such as:

1/- Continuity of its characteristics from previous nights (or hours),

2/- its elevation after Sunset,

3/- its relative directions from the setting Sun or the (moving) Moon,

4/- its ranking as the few brightest objects in the sky after Sunset.

Stars near to the elliptic may sometimes be confused with much brighter planets and their use involves extra cares.

If you are away from the two polar zones and always can see an unobstructed sky (nearly half of the Celestial sphere), you only need to find one of the 3 stars Orion Rigel, Boote Arcturus and Altair to apply this method.

4. Rules for turning to lower Celestial pole.

divider43.jpg

Figure: The rule for finding North by any chosen star is similar to the rule illustrated here for the Sun.

Be certain of your hemisphere and whether the star is rising (early star) or setting (late star) to turn the second leg of the divider to the left or to the right. This is similar to the requirement for finding North using the Sun.

Then apply all the steps of the next section.

5. Steps to find North direction and time using a star.

DirectionTimeByStars

Figures: Summary of steps to find North direction and time by any known star.

When any star is used on its date in the year, the Sun leads it by exactly 12 hours. For every month after that, the lead by the Sun is reduced by 2 hours (or every 12 months by 24 hours). The last figure of the illustration shows the Sun leading the star by about 5 hours on the Celestial clock face.

Example 1:

In December, January, February use Sirius if you can see it.

Sirius is a star of Jan 1st with declination 17 degree S. Step 8 of reference [2] shows how to find it.

On Jan 1st the time determined by Sirius is 12 hours behind the time by the Sun.

On April 1st, the time determined by Sirius is 6 (=12-3*2) hours behind the time by the Sun.

Example 2:

In March, April, May use Boote Arcturus if you can see it.

Boote Arcturus is a star of April 25th with declination 19 degree N. Step 6 of reference [2] shows how to identify it.

On April 25th the time determined by Boote Arcturus is 12 hours behind the time by the Sun.

On May 25th, the time determined by Boote Arcturus is 10 (=12-1*2) hours behind the time by the Sun.

On June 25th, the time determined by Boote Arcturus is 8 (=12-2*2) hours behind the time by the Sun.

References.

[1]. tonytran2015, Finding directions and time using the Sun and a divider., survivaltricks.wordpress.com, posted on May 6, 2015.

[2]. tonytran2015, Finding North and time by stars, survivaltricks.wordpress.com, posted on August 28, 2015.

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Click here for my other blogs on divider43.jpgSURVIVAL

Click here for my other blogs on divider43.jpgSURVIVAL

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