Indian mariners had first use of magnetic navigational compasses.

Indian mariners had first use of magnetic navigational compasses.

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. 163).

The magnetic navigational compasses may have been first used by Indian people and may not have been first invented by Chinese people as often claimed.

#compass, #navigation, #lodestone, #Chinese compass, #Olmec magnetic, #Indian, #yantra, #matsya yantra, #maccha yantra,

Indian mariners had first use of magnetic navigational compasses.

1. Claims that China invented the compasses.

Wikipedia said that

“The first compasses were made of lodestone, a naturally magnetized ore of iron, in Han dynasty China between 300 and 200 BC.”[1]

The entry on Han Dynasty said that

“The Han dynasty (/hɑːn/; Chinese: 漢朝; pinyin: Hàn cháo) was the second imperial dynasty of China (206 BC–220 AD).” [2]

Figure: Han Dynasy, from https://commons.m.wikimedia.org/wiki/File:Han_Dynasty_Plain_map.PNG#mw-jump-to-license

So the compasses are used in China after 206 BC, but it was initially only for geomancy.

“The magnetic compass was not, at first, used for navigation, but for geomancy and fortune-telling by the Chinese. The earliest Chinese magnetic compasses were possibly used to order and harmonize buildings in accordance with the geomantic principles of feng shui.” [1]

“The compass was later used for navigation by the Song Dynasty”[1]. (Song Dynasty: Chinese: 宋朝; pinyin: Sòng cháo; 960–1279)

So the written records on the use of compasses for navigation in China are made after year 960 CE.

Note that there were South-pointing chariots used in ancient China before year 235 CE [2b, 2c, 2d] but their operation was not based on magnetism. Their operation relied on the differential between the numbers of rotations of the left and right wheels (of same size) of each chariot to give its total yawing angle since departure.

Those chariots may have even been “first constructed by the Duke of Zhou (beginning of the 1st millennium BC) as a means of conducting homewards certain envoys who had arrived from a great distance beyond the frontiers.” [2b].

Figure: Model of a Chinese South Pointing Chariot, an early navigational device using a differential gear. Original file from
https://commons.m.wikimedia.org/wiki/File:South-pointing_chariot_(Science_Museum_model).jpg#mw-jump-to-license
by Author Andy Dingley, licensed under the Creative Commons Attribution 3.0 Unported license.

2. Appropriate places to look for records.

Many people look for easily read records. China certainly has many records which have been translated into English and are easily understood by readers in the World.

However, China is a land conquering empire, requiring little use of compasses while India is a sea faring trading empire which may benefit a lot from compasses. The logical place to look for records of first use of navigational compasses should therefore be India, an outreaching seafaring trading empire (as necessity is the mother of inventions). Indian influence is obvious over the vast area of Indian Ocean, Polynesian nations and (mostly South) Pacific Ocean [2e].

Any discovery of earlier use of magnetic navigational compass predating Chinese use should not surprise/disappoint investigators as the people of the trading Olmec nation (on the side of the Gulf of Mexico) has even used lodestones, hematite, magnetite since 1500 BC, one thousand year before any record of Chinese first use of lodestones [3], [4].

It is to be noted that China is on the East of India while Arab countries, Spain, Olmec are spread to its West.

3. Many evidences pointing to ancient use of compasses by Indian people .

The literature of the out reaching, sea faring nation India have many evidence to support its first use of the magnetic navigation compass.

“The compass was first used in India, around 1800 BC, for Navigational purposes and was known as “Matsya yantra” (which roughly translates to fish machine) because of the placement of a metallic fish in a cup of oil.” [5]

However, no evidence have been given in [5] to support the claim of “around 1800 BC”.

Reference [6] stated that
“In the Tamil nautical books, the use of compass is mentioned in the fourth century BC”,

4. Evidence on knowledge of magnetic attraction by Indian people since 500BC.

K. V. Ramakrishna Rao [7] pointed out that:

In Vedas, there is reference to “ayas” implying Iron and “Akarshan” attaction, thus, pointing to Iron-magnet relationship.[7]

Kanada (c.550 BCE) mentions about a needle that moves towards a magnet as –

“Manigamanam sucyabhi sarpanam drastakaranam” (Kanadasutra.V.I.15). In the commentary called the Upaskara, the passage has been clearly explained to signify that the needle goes towards the magnet.[7]. (Wikipedia [8] stated that Kanada was estimated to live between 6th and 2nd century BC.)

Kalidasa (c.500 BCE) records: “Siva’s mind has been fixed steadily because of penance. And therefore, now try to distract his attention just like an iron piece is attracted or drawn towards a magnet (ayaskantena lohavat akarshtum)” (Kumarasambavam.II.59).“[7]

The date of 500 BCE assigned for Kalidasa quoted by [7] may be in error. Wikipedia [9] stated that Kalidasa’s works cannot be dated with precision, but they were most likely authored within the 4th-5th century CE. In any event, it is not important, only the date of 550BCE assigned to Kanada is pivotal to the thesis of this article.

5. Evidence on compass use by Indian people since 500CE.

Milindapanho (VII.2.16) composed during 4th-5th centuries CE, mentions about an instrument used by the pilot of a ship for steering the ship.

“And again, O King, as the pilot put a seal on the steering apparatus, lest any one should touch it”.
“[7]

Rhys Davis translates the term as “steering apparatus” and it Sanskrit it is “yantra”, a mechanical devise, just like “matsya yantra” working on mechanical and accompanied with other principles.[7]

Mookerji points out a compass on one of the ships in which Hindus of the early Christian era sailed out to colonize Java and other islands in the Indian ocean. The Hindu compass was an iron fish (called in Sanskrit matsya-yantra or fish machine). It floated in a vessel of oil and point to the north (History of Indian Shipping, London, 1912) [7].

The following is what Mr. J.L. Reid, who was a member of the Institute of Naval Architects and Shipbuilders in England, has said in the Bombay Gazetteer, vol. xiii., Part ii., Appendix A.

“The early Hindu astrologers are said to have used the magnet, in fixing the North and East, in laying foundations, and other religious ceremonies. The Hindu compass was an iron fish that floated in a vessel of oil and pointed to the North. The fact of this older Hindu compass seems placed beyond doubt by the Sanskrit word Maccha Yantra, or fish machine, which Molesworth gives as a name for the mariner’s compass”. [10]

6. Conclusions

The thesis of this article is Indian mariners have already used magnetic navigation compass at least since 500 CE while Chinese had recorded usage of them only after 900 CE, a long four hundred years later.

It appears that the out reaching Indian seafarers had the first use of magnetic navigational compasses. Since necessity is the mother of inventions, it is natural to expect this as India had been an ancient seafaring trading nation.

References:

[1]. https://en.m.wikipedia.org/wiki/History_of_the_compass

[2]. https://en.m.wikipedia.org/wiki/Han_dynasty

[2b]. Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 2. Taipei: Caves Books, Ltd., pages 286, 289, 291, 298.

[2c]. https://en.m.wikipedia.org/wiki/South-pointing_chariot

[2d]. https://vi.m.wikipedia.org/wiki/Xe_ch%E1%BB%89_nam

[2e]. https://en.m.wikipedia.org/wiki/Tamils

OLMEC LODESTONES

[3]. https://en.m.wikipedia.org/wiki/Olmecs

[4]. https://misfitsandheroes.wordpress.com/2018/01/15/fat-boys-magnetism-and-magic/

INDIAN COMPASSES

[5]. .https://knowledge4civil.wordpress.com/2017/07/23/types-and-uses-of-compass/

[6]. http://www.whoinvent.com/who-invented-the-compass/

[7]. http://archive.worldhistoria.com/compass-in-india_topic17077.html

[6b]. https://en.wikipedia.org/wiki/Kanada_(philosopher)

[6c]. https://en.wikipedia.org/wiki/K%C4%81lid%C4%81sa

[10]. http://www.crystalinks.com/indiaships.html

[11]. http://bharatuntoldstory.tumblr.com/post/73862258619/maccha-yantra-the-ancient-indian-mariners

Added after 2019 Dec 24:

[12]. https://sea.mashable.com/science/8195/singapore-was-possibly-ruled-by-the-indian-chola-dynasty-1000-years-ago-australian-researcher-says

 

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Finding accurate direction by a watch

Method for finding accurate directions by a common analogue watch.

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.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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Finding North direction and time using the hidden Sun via the Moon . Posted on July 6, 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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The Southern Cross Pointer stars

 

The Southern Cross Pointer 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.111).

by tonytran2015 (Melbourne, Australia).

#find North, #finding North, #navigation, #alpha Centauri, #Agena, #Southern Cross, #pointers, #constellation, #Scorpius,

The Southern Cross Pointer Stars.

Celestial navigators who do not use declination and right ascension begin their navigation by learning the various bright, easily unmistakable constellations in the sky (There are no more than 10 to learn beginning with Orion constellation. and Scorpius constellation.). In the Southern Hemisphere, the Pointers to Southern Cross constellation are next to be learnt as they are very bright and most easy to identify.

The two Pointer stars are two very bright stars (alpha Centauri and Agena) in the Southern Celestial hemisphere. They are very useful as they help identifying nearby navigational stars and consequently finding Southern Celestial pole for navigation.

These two bright stars are circumpolar and are both 30 degrees from to the Southern Celestial pole. They are seen late night in February, all night in May, early night in September.

Inhabitants of Southern hemisphere need only to identify Alpha Centauri (brighter star of the pair), Agena (dimmer star of the pair), and Achernar in the clockwise direction (all at 60° South declination) to find the Southern Celestial pole which is at the center of the circle of 30 degrees in radius through these three stars. Achernar is almost 60 degree from the Pointers (alpha Centauri, Agena) and is opposite them across the Southern Celestial Pole.

Figure: Pointer stars pointing to the Southern Cross on a Polar Skymap for Southern hemisphere.

Extending the line alpha Centauri-Agena (from brighter to dimmer Pointer) by 8 degrees takes us to the Southern Cross Constellation. Then turning clockwise by 50 degrees and extending by an additional 50 degrees takes us to the very bright Canopus star which is nearly 40 degrees from the Southern Celestial pole.

In the opposite direction, extending the line Agena-alpha Centauri (from dimmer Pointer to brighter Pointer) by about 30 degrees takes us to the stinger tail of the large, distinctive Scorpius constellation (this line goes on for another 40 degrees to reach the bright tropical star Altair). From the direction of the line Agena-alpha Centauri (from dimmer to brighter Pointer) turn clockwise by 50 degrees and travel by about 45 degrees from alpha Centauri takes us to the moderately bright star Antares at the heart of the Scorpion.

Figure: Locating an individual star in a crowded area is easily carried out using a folded piece of cardboard: The folding line is aimed at the first known star, one cardboard flap is aligned to contain the second known star. The other flap is then opened to the required angle (marked 1) and the angle to the target star (marked 2) can be read.

2. The Southern Cross.

The Southern Cross is a useful navigational constellation. Its long axis goes through the Southern Celestial pole (which is also nearly on the bisector of the Pointer Stars and is also nearly on the line through Sirius and Canopus) in one direction and goes through the Northern Celestial pole in the opposite direction.

Turning slightly by 20 degrees anticlockwise toward the trailing’ side (Eastern side) from this direction to the Northern Celestial pole and travel by a distance of about 50 degrees from the Southern Cross takes us to the bright star Spica. Turning more anticlockwise towards the Eastern side by an additional 15 degrees from that direction and traveling an additional distance of about 30 degrees takes us next to the very bright star Bootes Arcturus (The direction from Spica to Bootes Arcturus is pointing about 25 degrees to the trailing side, Eastward, from the direction of a great circle arc toward the Northern Celestial pole.).

3. The dates of Pointers to Southern Cross.

Figure 1: The dates of Agena and alpha Centauri from the table of star dates.

The Pointer stars are seen in late night in February, all night in May, and in early night in September.

4. Taking photos of the Pointers.

Figure 1: The Pointers and Southern Cross Constellation are in the lower right quarter of this phpto taken with a Samsung Galaxy Note 2. The original photo has been digitally enhanced.

The Pointers and Southern Cross constellation are adequately bright and their photos can be taken using a smart phone such as a Samsung Galaxy Note 2 with no extra attachment.

The Pointers and 3 corner stars of the vertical Southern Cross are seen on the bottom right of the above two pictures. The dimmer fourth stars of the Southern Cross can be seen in the second photo. Antares is the bright star near the middle of the left border of the second picture. Antares and the front part of the Scorpius constellation are located near the center of the left border of the second picture (The very bright dot near the upper left corner of the picture is a planet.).

Figure 2: Photos of the Pointers and Southern Cross Constellation taken with a Samsung Galaxy Note 2. The original photos have been digitally enhanced.

The two bright Pointers are seen on the bottom right of this picture 2. The two brightest spots on the left half of this picture are two planets traveling on the Ecliptic. Antares is the bright star near the middle of the half left of this picture. Vertically above Antares is the front part of the Scorpius constellation. Vertically below Antares is the bright stinging tail of the Scorpius.

Figures 3: Photo of the Scorpius Constellation taken with a Samsung Galaxy Note 2 at the same time. The original photos have been digitally enhanced.

The Scorpius constellation just mentioned is captured in the center of the third photo. There are four brightest dots on the top of the picture. The far right and far left dots are very bright and are two planets traveling on the ecliptic. The planets on the ecliptic sometimes make confusing the identification of the stars at the front of this constellation.

References.

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

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

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

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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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Adding Longitude and Latitude Lines to a map

Adding Longitude and Latitude Lines to a map

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.78).

#find North, #GPS, #navigation, #off grid, #adding, #longitude, #latitude, #coordinate, #lines, #map,

Adding Longitude and Latitude Lines to a map.

Locating where you are using the internet is great but there are times when you have no mean to connect to the internet and you have to use GPS for positioning without any assistance via the internet. Such a situation may arise when you have no internet coverage or when going hiking.

If you want to use your GPS off-grid with any map, you need to draw on top of the map an accurate system of regularly spaced longitude and latitude coordinate lines.

This posting shows how to add the lines.

1. Making a map graduated with Longitude and Latitude Lines.

1. Choose a map with your required resolution and range. The resolution differs for different application: For city street maps resolution should be better than 2m, for country town maps, resolurion only need to be better than 5m as houses are widely separated, for touring, exploring maps, resolution can be upto the (1/10) of the visual range, etc…

2. Make sure that the top of the map points to true North. (In some countries, maps are deliberately oriented at angle to true North, probably for security reasons.)

Figure: Openstreetmap for Melbourne with 3 airport landmarks. Map is used under Open License from Open Street Map, the data are owned by Open Street Map Contributors.

3. On that map, find some unmistakable features such as a well known Airport or Helipad, a Light House, a TV Transmission Tower, a Town Hall, Churches, Schools, Cottages in a forrest, sharply defined mountain peaks, trail intersections… with known longitudes and latitudes. Their coordinates are usually given on the Internet or or easily extracted from Google Map or Navigating Apps.
Find two to four such fearures located near the four extreme corners of your map. They will be used as land marks.

Ecample:

The 3 landmarks that can be used here are:

a. Melbourne Tullamarine airport, Elevation AMSL 434 ft / 132 m, Coordinates 37°40′24″S 144°50′36″E

b. Melbourne Moorabin airport, Elevation AMSL 50 ft / 15 m, Coordinates 37°58′33″S 145°06′08″E

c. Melbourne Essendon airport, Elevation AMSL 282 ft / 86 m, Coordinates 37°43′41″S 144°54′07″E

4. On a separate fresh sheet of paper make a coordinate grid of longitude and latitude covering your range.
On this sheet with grid but no map, mark the coordinates of your land marks.

Figure: Melbourne Tullamarine and Moorabin airports on a grid map.

5. Check that the shape of the figures formed by the land marks are similar in both the grid sheet and the map. You may have to stretch or shrink the grid vertically and then horizontally to have a fit. The figures should be similar if no mistakes have been made. If the shapes are similar you can proceed to the next step.

6a, If the map and grid are both digital, they can be superimposed in the computer to produce the following map with added coordinate lines:

Figure: Openstreetmap for Melbourne with added cooodinates. Map has been modified from original map used under Open License from Open Street Map, the data are owned by Open Street Map Contributors.

The added lines are on round figure coordinates and are 2 minutes of arc apart. The intersection nearest to the NW of Tullamarine airport has coordinate (144°50′E, 37°40′S ).

6b. If you are using printed map: Join two distant landmarks on the coordinate sheet and notice where the lines of “minute of longititude” and of “minute of latitude” intersect it

7. If you are using printed map: Reproduce that line, with all its intersecting points, on the actual paper map.

8. If you are using printed map: From these intersecting points project corresponding vertical lines to make the “minute of longititude” lines and horizontal lines to make “minute of latitude” lines.

9. The map is now graduated with longitude and laritude lines.

10. Its grid can now be used as a base to draw finer grids for detail maps with higher resolutions.

2. Using GPS with maps.

You can download a (preferably topological) map of your area to practice drawing the coordinate lines, the constant altitude lines and learn about the accuracy of the values of longitude, latitude and altitude given by your GPS apps.

It is preferable to use topographic maps with old fashioned land marks (such as churches, tall towers …). Topographic maps give the additional constant ground altitude contours (relative to some mean sea level surface). Constant altitude curves are the faint brown curves on the map illustrated here. The height of each contour is given by a small number. The altitude values of 20m and 10m have been highlighted in this example map by two red circles.

Figure: Opentopomap for the area in my test. Map is used under Open License from Open Street Map, the data are owned by Open Street Map Contributors.

References

[1]. tonytran2015, Using GPS in off-grid situations., posted December 6, 2016

[2]. tonytran2015, Measuring angles and distances for outdoor survival, survivaltricks.wordpress.com,

https://survivaltricks.wordpress.com/2016/06/29/measuring-angles-and-distances-for-outdoor-survival/, posted 29/6/2016.

[3]. tonytran2015, Selecting and using magnetic compasses, survivaltricks.wordpress.com,

https://survivaltricks.wordpress.com/2016/07/09/selecting-and-using-magnetic-compasses/, posted 09/7/2016.

[4]. , BBC News, UK radio disturbance caused by satellite network bug, http://www.bbc.com/news/technology-35463347, 2 February 2016.

Added after 2018 Nov 26:

The Thors’ son urged people travelling to remote locations without mobile coverage to download a GPS application to their phones ahead of their journey, as well as an offline map for their destination.

[5]. https://mobile.abc.net.au/news/2018-11-26/german-tourists-died-central-australia-walked-17km-heat-stress/10554408

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Finding North in the polar zones using Equatorial Stars and the Sun.

Finding North in the polar zones using Equatorial Stars and the Sun

by tonytran2015 (Melbourne, Australia).

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(Blog No.66).

#find North, #finding North, #polar zone, #arctic zone, #Equatorial stars, #Sun, #Viking, #navigation .

Finding North in polar regions using Equatorial Stars and the Sun.

The general principles in Finding North still apply for each familiar method. However Finding North direction in polar regions has its own problems and it is not as simple as for temperate zones due to difficulties caused by steep magnetic lines not pointing to rotational poles, by the closeness of the upper Celestial pole to the zenith, by long extended day time, by aurora light, by aurora interference with radio wave receivers in GPS units.

When those familiar methods encounter problems the method of Finding North by Tropical stars and the Sun can still work and maintain its precision. The Viking may had used this technique in their long sea voyages many centuries ago.

1. The two polar zones

The two polar zones cover any area with absolute value of latitude higher than 66°33′. That is all their points are less than 23°27′ from one of the two poles. The Northern polar (arctic) zone covers parts of Greenland, Iceland, Sweden, Norway, Finland, Russia, U.S. Alaska, Canada with many of their cities. The Southern polar (antarctic) zone covers parts of Antarctica continent (with Argentinian stations, UK Rother station, etc …).
The ratio of the lengths of Day versus Night varies with a yearly cycle on any point of the Earth. In Arctic zone, it reaches 0-100 for some period centered on Winter solstice (on 21 December ) when the Solar path is totally below the horizon. The ratio then varies from 1-99 to 99-1. It then reaches 100-0 for some other period centered on Summer solstice (on 21 June ) when the Solar path is totally above the horizon. The ratio then varies from 99-1 to 1-99 and reaches 0-100 again.
It is similar for Antarctic zone except for the 6 months time difference between the two polar zones.

2. Finding North by GPS.

Find North by a GPS

Figure: A GPS screen.

The easiest way to find North in a polar region is to use the GPS apps on smart phones or on purpose made GPS units.

GPS compass directions are calculated from the change in terrestrial coordinates when you move. The minimum movement distance is only about 5m.

GPS compass directions are true directions and are different from and independent of magnetic compass directions.

However, GPS units may run out of battery, be non-operational during war times, be under heavy interference from polar aurora storms. A non-GPS back up method is still necessary.

3. Finding North by a magnetic compass.

Find North by a compass

Figure: A magnetic compass.

3a. The magnetic poles are not exactly at the North and South poles of the Earth. They are currently in Canada and near to New Zealand respectively. Users of magnetic compasses should know how to compensate for this.

3b. Magnetic lines are also nearly vertically inclined in polar regions making normal compasses sticky with their needles and they may have to be replaced by cruder magnetic rods hung on wire threaded through holes near to their mid-points.

3c. Aurora in the sky changes very slowly and can be used as overhead navigational marks juat like permanent clouds.

4. Finding North using Polaris.

mercator8fx1.6polarc30.jpg

Figure: The Northern and Southern Polar skymaps are represented by two circular discs here.

A real dipper versus Big and Little Dipper constellations

Figure: Photo of a real dipper. Inset: The Big Dipper and Little Dipper constellations.

4a. Polaris in the Little Dipper is right on the North Celestial pole. The North Celestial pole is in the Northern direction of all vertical plumb lines. If the star can be obscured by any plumb line then you eye is exactly on the South of the line. Near to the pole, Polaris is close to the upper extension of any vertical plumb line and it is hard to obscure it by some vertical plumb line.

4b. The altitude of Polaris is most easily read with a Bubble Sextant (Aircraft Sextant) or with a Theodelite (for higher accuracy). The direction with smallest value of altitude of Polaris is Northern direction.
The method is easily applicable at night time but Polaris cannot be seen during day time and during aurora storms.

5. Basis of finding North by Tropical stars.

Find North with Orion Equatorial starsFigure: Panoramic view of the Celestial Equator and the Tropical band from the Arctic zone in December. Stars travel from Front Left to Front Right. The directions and Solar times corresponding to the scale on the bottom of the picture are N(0hr)-E(06hr)-S(12hr)-W(18hr)-N(24hr).

5a. Any point on the Earth sees exactly half of the Celestial Equator above its horizon. The angle between the plane of this half circle and the horizontal one is equal to (90°- latitude).
The Celestial Equator is inclined to the ground and is below the horizon in the North direction in the Northern hemisphere.

5b. Equatorial stars such as the Central Belt Star of the Orion travel along this circle once every day. They rise and set exactly in the exact East and exact West directions respectively.

Find North with Scorpius Equatorial starsFigure: Panoramic view of the Celestial Equator and the Tropical band from the Antarctic zone in June. Stars travel from Front Right to Front Left. The directions and Solar times corresponding to the scale on the bottom of the picture are S(24hr)-W(18hr)-N(12hr)-E(06hr)-S(0hr).



5c. Any tropical star (any star which is no further than 23°27′ from the Celestial Equator) travels along one large (but not great) circle in the sky every day. The circle is “parallel” to the Celestial Equator.

5d. The elevation/altitude of the star varies daily with an amplitude equal to (90°-observer’s latitude) about its daily mean (which is nearly equal to its Declination multiplied by the sine of observer’s latitude)

5e. The North Souih line is the bisector of two directions pointing to any two positions having equal elevations of the same star. The common elevation can be conveniently chosen to be the mean of its 24hr values.

6. Solar trajectory on the Celestial Sphere

The Sun travels along one large (but not great) circle in the sky every day. The circle is “parallel” to the Celestial Equator. The circular Solar path drifts to its most Northern position at 23°27′ latitude on 21 June solstice then drifts to its most Southern position at 23°27′ latitude on 21 December.

At equinox times, the Sun is exactly on the Celestial Equator and rises and sets exactly like an equatorial star.

Locating the hidden Sun by polarized lightFigure: Locating the hidden Sun by polarized light from bright patches of the sky.

Knowing the trajectory of the Sun, you can locate it using polarizing sunglasses even when it is hidden and under the horizon (see ref. [5], Using polarized light to locate the Sun when it is hidden from view).

7. Measuring solar altitude with a stretched hand on an extended arm.

A hand with stretched out fingers hold on its extended arm sustains an angle of about 12 degrees and is a very convenient mean for measuring Solar elevation (altitude) angle in polar regions.

8. Variation of Solar altitude/elevation during the day.

Solar elevation/altitude varies daily with an amplitude equal to (90-latitude) about its daily mean (which is nearly equal to Solar Declination of the day multiplied by sine of local latitude).

You can tell where is the Sun on its daily cycle by measuring its altitude with a stretched hand on an extended arm.

As the Sun travels on a known wavy line its altitude gives both its compass direction and the corresponding time of the day.

The directions and times corresponding to the scale on the bottom of the first panoramic picture (for Arctic regions) are N(0hr)-E(06hr)-S(12hr)-W(18hr)-N(24hr).

For Antarctic regions the directions and times corresponding to the scale on the bottom of the second panoramic picture are S(24hr)-W(18hr)-N(12hr)-E(06hr)-S(0hr).

9. Time estimation from Solar altitude

Solar altitude may give a better time estimation near to Sunrise and Sunset.

The time is 6hr or 18hr when the altitude of the Sun crosses its mean value.

10. Distinguishing AM from PM

When using the Sun for navigation, it is important to know whether the Sun is ascending (AM) or descending (PM).

10a.A 24hr sub-dial on a clock face is certainly useful in telling AM and PM.

10b. Ambient air temperature after receiving daylight radiation is also usually higher in PM time than in AM time.

10c. There are different sets of stars in the sky for AM and PM in the night.

10d. Birds activities are different in AM and PM.

10e. Your biological clock (circadian rhythm) may help distinguishing AM and PM.

11. Finding North with a watch in a polar region

Finding North with a watch

Figures: Finding North with a watch for antarctic and arctic zones.

Finding North with a watch needs a modification: If you can travel to the nearest pole in 2hr, you have to remember that the 6-12 line on the watch points along the meridian line of your home city, not toward the Pole of the Earth. Indeed, you can travel around the pole but that 6-12 line keeps its direction along the meridian of your home city.

The watch face can be simply laid horizontally as in the original “Scout method” without generating any noticeable directional error.

Figure: A map of the arctic from National Oceanic and Atmospheric Administration (https://www.pmel.noaa.gov/rediscover/resources). All meridional lines converge at the pole.

12. Finding North with a divider in a polar region

solar declination from a watch face

Figure: Estimating Solar declination by drawing a watch face with a subdial.

Finding North by a divider

Figure: Finding North by a divider.

The divider method is still applicable for finding direction and time but requires high accuracy in Solar declination and latitude angle for setting the divider.

A small plumb line hanging from the stem of the divider can improve the accuracy for its latitude angle setting.

With the above additional plumb line, the divider can measure the altitude of the Sun to give a good estimate of time.

13. Finding North with an AM Broadcast radio receiver in a polar region

AM radio usable for Finding North direction

Figure: An AM Broadcasting radio receiver wirh an internal ferrite rod antenna.

The method of finding direction using an AM radio receiver tuned to nearby broadcasting ([8]) is useful near to cities with AM broadcasts in polar regions. The transmission is not effected by low visibility from bad weather. You need a map of the region with AM transmitters as landmarks.

References.

[1]. tonytran2015, Using GPS in off-grid situations., https://survivaltricks.wordpress.com/2016/12/06/using-gps-in-off-grid-situations/, posted December 6, 2016

[2]. tonytran2015, Selecting and using magnetic compasses, survivaltricks.wordpress.com, https://survivaltricks.wordpress.com/2016/07/09/selecting-and-using-magnetic-compasses/, posted 09/7/2016.

[3]. 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.

[4]. 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

[5]. tonytran2015, Using polarized light to locate the Sun when it is hidden from view, https://survivaltricks.wordpress.com/2015/05/09/using-polarized-light-to-locate-the-sun-hidden-behind-clouds/, posted on May 9, 2015

[6]. 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

[7]. 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.

[8]. Navigating with an AM MW radio receiver.

[9]. https://www.pmel.noaa.gov/rediscover/resources.

RELATED SURVIVAL blogs:

Using polarized light to locate the Sun when it is hidden from view. . Posted on May 9, 2015. This is a useful technique.

Using GPS in off-grid situations., posted December 6, 2016

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

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Navigating with an AM MW radio receiver

Navigating with an AM MW radio receiver

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.48).

#AM, #broadcast, #emergency, #radio, #radio direction finding, #find North, #Medium Wave, #radio navigation.

Every natural disaster emergency kit is recommended by authorities to include a battery operated Amplitude Modulation Medium Wave (AM MW, also called AM Broadcast) radio receiver to receive critical information and instructions.

The radio receiver can actually do much more than receiving information and instructions. It can find the direction to nearby AM broadcasting stations and even find your location on any map showing the stations.

Figure: Map of Melbourne with 2 nearby AM broadcasting stations shown as red dots. Map has been modified from original map used under Open License from Open Street Map, the data are owned by Open Street Map Contributors.

The technique is applicable when there are nearby (closer than 100km) AM broadcast stations. It is useful to regions near the terrestrial magnetic poles where magnetic compasses do not work well, to desert crossing and to coastal boat travel when visibility is very poor and other modes of navigation are not available (such as when in bad or extreme weather, during volcanic emergency and without any working magnetic compass).

1. Basis of Radio-direction-finding.

An AM broadcasting station in Medium Wave sends electromagnetic waves out from its antenna at the speed of light. The invisible EM waves propagate outwards from the broadcast station’s vertical antenna. The antenna continuously releases consecutive, expanding circular magnetic lines of alternating (clockwise then anti-clockwise) orientations. The circles spread out in all directions. When a receiver receives the signal, the alternating magnetic field is at right angle to both the spreading (propagation) direction and the alternating electrical field which is almost in the direction of the broadcasting antenna.

Most AM radio receiving Medium Waves (0.5MHz to 1.6MHz) use ferrite rod antennas to capture these magnetic field lines. The ferrite rod of an AM MW receiver is usually placed inside and along the top edge of the (usually flat) receiver. Figure 4 shows the ferrite rod antenna inside a Sony radio of a common design.

sharp radio

Figure 1: A battery operated multi-band AM radio that can be used in emergency. This battery operated multi-band AM radio with a fair sized signal strength indicator in a small window on the left of the dial was made in the 1960’s. Its pulled out rod antenna is only for Short Wave reception, an internal long ferrite rod antenna is used for Medium Wave reception.

radiosony

Figure 2: A compact radio receiver WITH an AM internal ferrite rod antenna that can be best for emergency use. This compact AM/FM receiver has an internal ferrite rod antenna for AM MW reception and can properly receive AM signals even without using any earphone.

When an AM MW (also called broadcast band) radio receiver has been tuned to a station, you can notice the signal strength varies when its ferrite rod antenna is rotated on the horizontal plane: The received signal is weakest when either end of the rod is pointed directly at the transmitting station, and it is strongest when the rod is at right angle to the line of sight to the station. The technique has been widely used for ships until the advent of low cost GPS. Reference [1] gives a really interesting long list with pictures of AM radio receivers specially built for the application of this technique on ships.

Figure 3: A 3 band Sony transistor radio with a retractable short wave rod antenna (radio model 838, assembled in South Vietnam in 1970, under license from SONY, as shown on the label on the back of the radio).

direction by ferrite rod antenna

Figure 4: The interior of the Sony transistor radio showing a long ferrite rod antenna of grey colour on the top and parallel to the top edge. (Sony radio model 838, assembled in South Vietnam in 1970, under license from SONY, as shown on the label on the back of the radio.)

CAUTION: Many compact AM MW radio receivers do NOT have ferrite rod antennas, they use their earphone wires to receive the electrical component of the broadcast waves. This method of finding directions does NOT work with such receivers.

2. Finding direction by a radio.

Rotate the top edge (with the ferrite antenna) of the receiver by a full horizontal turn and notice the two opposite directions where signal receptions are weakest. When this happens, one of the ends of the ferrite rod is pointing exactly at the station and the station lies on the line through the top edge of the receiver. Additional information from somewhere else is needed to tell in which of the opposite directions the station may lie.

Figure: Openstreetmap for Melbourne with added cooodinates and the locations of Delahey and Lower Plenty. Map has been modified from original map used under Open License from Open Street Map, the data are owned by Open Street Map Contributor.

Examples:

a. “ABC Radio Melbourne ‘s 774 kHz transmitter is located in Delahey (the left red dot in the map), 20 km north-west of Melbourne’s central business district. … at a power of 50,000 watts,… one of two transmitters using the callsign 3LO” [2].

When an AM radio is tuned to 3LO on 774kHz it receives the broadcast with call sign 3LO. When its ferrite antenna is pointed at the left red dot on the map, the signal will be weakest and the reception most noisy.

b. ABC NEWS on radio ABC NEWS on radio Frequency 1026 AM Callsign 3PB Sound Mode Mono Polarisation Vertical Broadcast Pattern OmniDirectional Transmitter Location Bonds Road LOWER PLENTY (the right red dot on the map)” [3].

When an AM radio is tuned to 3PB on 1026kHz it receives the broadcast with call sign 3PB. When its ferrite antenna is pointed at the right red dot on the map, the signal will be weakest and the reception most noisy.

You may be able to find the frequencies and transmitter locations of the AM broadcasts for your area from the useful sites [4] www.dxing.info, [5] wiki List of European medium wave transmitters

3. Finding location by a line through the station.

If the direction of the top edge of the receiver relative to true North is known, the locus of the receiver on the map is a straight line through the broadcasting station.

Your location can be found using the intersection of two such locus lines through two broadcasting stations shown on a map. (The intersection R of the lines RS1 and RS2).

4. Finding location by a circle through two stations.

If two stations S1 and S2 are shown on a map and A is a directed (signed) angle from the line to S1 to the line to S2 then the locus of the radio receiver is the circle through S1 and S2 bearing that directed angle A.

For example, if the angle from R-S1 to R-S2 is 40 degrees (an example value) in the anti-clockwise direction, the receiver must be on the red circle drawn through S1 and S2 on the map. The example circle is called the circle bearing the angle of 40 degree in the anti-clockwise direction for viewing the (direcred) line segment S1-S2.

5. Finding location by three circles through three stations shown on a map.

arc bearing

Figure 1: Finding your location using intersecting angle bearing circles.

Any map showing the locations of the broadcasting stations S1, S2, S3,… can be used to locate the position R of the radio receiver. Any receiver with the angle from R-S1 to R-S2 being 40 degrees clockwise (an example value) in the clockwise direction must be on the circle drawn through S1 and S2 for that example value of 40 degrees. The example circle is called the circle bearing the angle of 40 degree in the clockwise direction for viewing the line S1-S2.

If three stations S1, S2 and S3 are shown on a map as in the figure of the last section and the directed (signed) angles between the directions to S1, S2, S3 are all known, the receiver is on the intersection of all three circles through each pair of S1, S2 and S3 bearing the respective directed angles between them. Usually, only two circles are needed to draw the intersection point, which is the location of the radio receiver R.

6. Limitation of the method.

a. The method works well if there are non-interfering AM broadcast stations within 100km of the navigator and the terrain is nearly flat.

b. When there are high atmospheric electrical activities it may be hard to find the direction for weakest reception by the ferrite rod of the broadcasting signals.

c. Many compact AM MW radio receivers do NOT have ferrite rod antennas, they use their earphone wires to receive the electrical component of the broadcast waves. This method of finding directions does NOT work with such receivers.

d. The method does NOT work with Shortwaves as shortwave signals are not received through ferrite rod antennas.

e. Note that Philips from Holland had a famous radio model, L4X00T, with a fold up/fold down rectangular antenna loop for shortwaves, which can also be used to find out the direction of the incoming shortwaves in the same way as described in preceding sections. However shortwaves bounce and they do not accurately show the directions to the stations.

f. For the method to be useful after an Electro-Magnetic-Pulse event, the receiver and the broadcasting stations should all survive the event. You may have to wrap your radio receiver in many layers of Aluminium foils and the broadcasting stations must know how to protect themselves against EMP events.

Reference.

[1]. Radio Direction Finders, angelfire.com, http://www.angelfire.com/space/proto57/rdf.html, accessed 06 Feb 2017.

[2]. https://en.m.wikipedia.org/wiki/ABC_Radio_Melbourne

[3]. http://www2b.abc.net.au/reception/frequencyfinder/asp/details.asp?transmissionid=2956.

[4]. http://www.dxing.info/lists/

[5]. https://en.m.wikipedia.org/wiki/List_of_European_medium_wave_transmitters

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The Scorpius constellation

The Scorpius constellation

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.45).

#find North, #finding North, #direction, #by stars, #Scorpius, #Antares, #Sagittarius, #Ara, #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 Scorpius is usually chosen to be the second constellation to be learned since it is as large as Orion and is useful when Orion is out of sight.

The Scorpius is a crowded, large Southern constellation of June. Part of it is always seen in the sky of June for the whole night, attains its highest elevation (or altitude) about midnight and is immediately South of the most Southern point of the Ecliptic. Scorpius can be seen on the rising side before sunrise in January, seen for the whole night in May and seen on the setting side after sunset in November.

It has the size of 30 degree (in angle) and has the shape of a hook oriented 55 degree clockwise from the great circle arc through the Celestial poles. Arabian sky watchers see a resembling to the body and tail of a (now declawed) scorpion and gave it the name Scorpius.

The brightest star of Scorpius is Antares but it is so close to the ecliptic that it is often outshone by the Moon and bright planets traveling on the ecliptic. Antares often requires extra care for proper identification. Identifying Antares give a good practice to star identifying.

1. The Scorpius on a Mercator sky-map.

mercator8gc30.jpg

Figure 1: The Scorpio constellation is in the shape of a hook, is close to the ecliptic and one third from the left edge of this Mercator sky-map.

Figure 2: A common Asian scorpion.

The Scorpius has too many stars and its brightest star Antares can even be over-shone by planets wandering near to it. Therefore its identification often requires additional care.

An observer in the Southern hemisphere can check that the hook shaped stinging tail of the Scorpius is just touching the great circle arc (drawn in yellow) through the two Pointers to the Southern Cross.

Figure 3: The Scorpius is seen as a hook in the top left quadrant of this Polar Inversion map of the Southern hemisphere. Its hook shaped stinging tail is just touching the great circle arc (drawn in yellow) through the two Pointers to the Southern Cross.

2. An alternative method of recognizing stars in the Scorpius

Figure 1: Scorpius Sagittarius and Ara are easily recognized together.

I found that it is easier to recognize the bright stars of three constellations Scorpius, Sagittarius and Ara together. They resemble a tree with two side roots rising at right angle from a ground line.

The two brightest stars of all three constellations are Antares and Shaula in the Scorpius.They are separated by 17 degrees in angle. They line up with two other dim stars to form a straight line (delta Scorpius, Antares, Shaula and kappa Scorpius) which is slightly longer.

The South-trailing end of this line continues to be the bisector of a right angle line formed by five stars zeta Sagittarius, Kaus Australis, Shaula, theta Scorpius, alpha Ara.

The line of two brightest stars looks like a tree sticking up at right angle to the ground line formed by dimmer stars in line with alpha and epsilon Ara. The tree has two side roots (Shaula-Kaus Australis. and Shaula-theta Scorpius-alpha Ara) originating from Shaula and each is at 45 degree from the tree trunk.

After the bright stars have been identified, each constellation can be identified using its conventional map as given in [1] and [2].

3. Taking photos of the Scorpius.

The Scorpius is adequately bright and its photos can be taken using a smart phone such as a Samsung Galaxy Note 2 with no extra attachment.

Figure 1: A photo of the Scorpius Constellation taken with a Samsung Galaxy Note 2. This photo was added on 2018Feb26 and has been digitally enhanced.

The Scorpius constellation is in the center of this picture. There are four brightest dots on the top half of this picture. The far right and far left dots are very bright and are two planets traveling on the ecliptic. The planets on the ecliptic sometimes make it hard to identify this constellation. (This added photo was taken on 2018 Feb 26).

Scorpius

Figure 2: Photo of the Scorpius Constellation taken with a Samsung Galaxy Note 2. The original photo was taken prior to 2017Jan09 and has been digitally enhanced.

Scorpius

Figure 2: Another photo of the Scorpius Constellation taken with Samsung Galaxy Note 2. The original photo was taken prior to 2017Jan09 and has been digitally enhanced. There are three bright dots in a straight line at the top of the first photo. The two on the left are two planets on the ecliptic. The third one on the right is delta Scorpius. Antares is the bright dot under the three in line.

4. Easy identification of Scorpius by a slide sky map.

starmap18april0130c.jpg

Figure 1: The Scorpius position by the Mercator slide sky map, with an altitude grid for an observer on 10 deg North (South of India, Thailand, Malaysia, South of Vietnam, the Phillipines, Central America) .

Observers who are not quite familiar with the Scorpius constellation can use the slide sky map described in reference [2] to confirm its identity. The latitude of the observer, time, and North direction are required for identification using a slide sky map. The figure here gives its altitude (elevation) and its orientation at the time of the first photo of the preceding section.

References.

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

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

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

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

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The Orion constellation.

​The Orion constellation

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.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.

mercator8gc30.jpg

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.

References.

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

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

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

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Slide Sky-Disks with grid masks showing azimuths and altitudes.

Slide Sky-Disks with grid masks showing azimuths and altitudes

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.28)

#find North, #finding North, #direction, #time, #slide, #sky, #star, #map, #disc, #disk, #star disk, #slide sky map, #slide sky disk, #slide star disk, #navigation, #declination, #right ascension.
Feature Figure: Illustration of a rotatable Sky map with an overlaid grid mask showing azimuths and latitudes of stars for a user at 40 degree latitude.

(Note: There was a software error which initially set the publication date wrongly on October 19th, 2016. The true publication date is Nov 3rd, 2016.)

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 night sky with current commercially available circular star maps as they are equidistant-azimuthal and have a lot of distortion for 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 curves should be nearly circular around the zenith point.

The device given in this posting gives the desired displays with low distortion for the night sky. I give it the name Slide Sky-Disk (which is similar to the name Circular Slide Rules of similar looking mathematical devices used before the age of calculators).

It is made of two maps of stars and of interchangeable viewing grids to give elevation and azimuth angles of stars to observers located near to 0 degree, 20 degrees, 40 degrees and 60 degrees in latitude.

It will be useful to people who want to learn the stars by themselves or need to refresh their nightly detailed knowledge of the sky before going out. It is low cost, light weight, small, flexible, durable and quite portable. If made from waterproof materials, it may also be used as a low cost standby star maps for pilots, travelers, hikers and seamen (My is made from CD discs, flexible CD cases and plastic films, they are all waterproof).

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

Step 1: Making the base maps for the Slide Sky-Disks.

Sky-disk for Celestial Northern 3/4-sphere

Sky-disk for Celestial Southern 3/4-sphere

Figures 1, 2: Two base maps.

The two maps of the North and South regions of the Celestial sphere made by Inversion Projection (Stereoscopic Projection) are used for the Northern and Southern hemispheres respectively.

The maps are to be printed on both sides of a thick sheet of A4 paper to make a base disc. Alternatively they can be printed on ordinary A4 papers and pasted on the opposite sides of a thick disk used as the base disc. I used 2 CD discs and print the maps as their labels.

Step 2: Making rotatable overlaying masks giving azimuth and elevation on the Slide-Sky-Disks.

altitude azimuth grid mask for 00 degrees of latitude

altitude azimuth grid mask for 20 degrees of latitude

altitude azimuth grid mask for 40 degrees of latitude

altitude azimuth grid mask for 60 degrees of latitude

Figures 1, 2, 3, 4: The grid masks for observers at 0 degree, 20 degrees, 40 degrees and 60 degrees in latitude.

A grid mask is placed on top of the base map to read the azimuth and the elevation of the stars drawn on the map. The grid masks must match the type of coordinates used for drawing the Celestial sphere. An observer must use the mask drawn for his latitude.

Description of curves on grid masks:

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 (or True South for Southern latitudes). 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 North line points toward the map’s center in Northern hemisphere and away from it in Southern hemisphere.). The red circular arcs represent the constant elevation circles in the sky. They are placed at 30, 60 and 90 degrees from the zenith. The circle 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.

Four grid masks are given here for use with both Celestial spheres. You have to select one that is based on a latitude nearest to your current latitude.

For latitude between 0 degree and 10 degree select the mask based on 0 degree latitude.

For latitude between 10 degree North and 30 degree select the mask based on 20 degree latitude.

For latitude between 30 degree North and 50 degree select the mask based on 40 degree latitude.

For latitude between 50 degree North and 70 degree select the mask based on 60 degree latitude.
You can make all four 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 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.

Step 3: Making the grid holder for a Slide-Sky-Disk.

Figure: The grids holder is made from a flexible CD case.

The grid holder is made from a flexible plastic CD box. The front circular window has been cut for viewing the map. A small rear window is cut for moving the map. A grid is drawn onto a square transparent film and fitted to the front cover. It is to be held in place by the four plastic lugs (visible in the picture). The base map will be fitted on to the holding stub on the back cover and it can be rotated relative to the case and the grid on the front cover.

Step 4: Final assemblage of a Slide-Sky-Disk.
slide-sky-disk

Figure 1: Photograph of an actual Slide Sky-Disk fitted with a mask for 40 degree.

slide sky disc rotated

Figure 2: Photograph with Sky-Disk rotated anti-clockwise by about 25 degrees.
Push the CD with the picture of the chosen hemisphere onto the holding stub of the CD case. Make sure that it can be easily rotated inside the holder. Close the case and the Slide Sky-Disk is ready for use. The disc is rotated by access through the small window on the back cover.

Step 5: Using the Slide-Sky-Disks.

The sky at night is represented by the circular sky map centered on the corresponding Celestial pole under the transparent window carrying the grid showing azimuth and altitude (that is the disc rotates under the viewing window).

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

2/- Rotate the map to place the current date on the opposite side of the window. The map and the grid gives the view of the mid-night sky for the date.

3/- Then rotate the core map by half a division (15 degree on the equator or half a month) to decrease or increase the Right Ascension for every hour ahead of or after midnight. R.A. increases in the clockwise direction for Northern and counter-clockwise for Southern hemisphere.

4/- As the latitude for the grid is not being exactly that of the observer and the true time at the location is not being equal to the zonal time the slide star disk may not give very accurate values of elevation and azimuth angle for the stars within 30 degree of the zenith. However the lines joining these stars still give accurate directions and they help identifying other stars near the horizon. The stars near the horizon can be read from the Slide Sky-Disk with more accurate values of azimuth and elevation angles.

Examples:

The sky of December 21st can be visualized for any latitude using these Slide Sky-Disks in combination with a Slide Sky Map [3] .The view is CORRECTLY ORIENTED WHEN its December marking ON EACH DISK IS AT THE BOTTOM. You may have to click on each image to have a clearer view.

Sky map for Dec 21st at latitude of 60°N

 Sky map for Dec 21st at latitude of 40°N

Figures 1,2: Night sky on Dec 21st at latitudes of 60°N, 40°N, up side down view. The view is CORRECTLY ORIENTED WHEN its December marking ON EACH DISK IS AT THE BOTTOM.

 Sky map for Dec 21st at latitude of 20°N

 Sky map for Dec 21st at latitude of 20°N

Figures 3,4: Night sky on Dec 21st at latitudes of 20°N, upside down view. The view is CORRECTLY ORIENTED WHEN its December marking is AT THE BOTTOM ON THE DISK.

 Sky map for Dec 21st at latitude of 0°

 Sky map for Dec 21st at latitude of 0°

 Sky map for Dec 21st at latitude of 0°

Figures 5,6,7: Night sky on Dec 21st at latitude of 0°N. The view of Figure 5 is CORRECTLY ORIENTED WHEN its December marking is AT THE BOTTOM ON THE DISK.

 Sky map for Dec 21st at latitude of 20°S

 Sky map for Dec 21st at latitude of 20°S

Figures 8,9: Night sky on Dec 21st at latitudes of 20°S.

 Sky map for Dec 21st at latitude of 40°S

 Sky map for Dec 21st at latitude of 60°S

Figures 10,11: Night sky on Dec 21st at latitudes of 40°S and 60°S.



References.

[1]. tonytran2015, Finding North and time by stars. Posted on August 28, 2015

[2]. tonytran2015, . Posted on May 25, 2016

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

RELATED SURVIVAL blogs

, posted on Circumpolar Stars Nth
, posted July 22, 2016

NorthByKnownStar

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, Slide Sky-Disks with grid masks showing azimuths and altitudes, Slide Sky-Map for displaying tropical stars.

Click here for my other blogs on divider43.jpgSURVIVAL

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