A point of reference plays a very vital role within the ambit of a horoscope. When measuring distances or ascertaining directions, we always assimilate the same based on a central point and do the evaluation. Likewise when viewing the position of planets in the sky, it is imperative to know where they are located and their co-ordinates from a particular reference point. Without a reference object, it wouldn't really matter how further they are positioned in the sky or make any sense as to the impact effected by them.
In the parlance of a horoscope, it is always the Earth which acts as the central pivot based on which planetary longitudes and latitudes are computed and the impact caused by them based on their placement in different signs and houses. This is in effect the main reason we do not see the 'Earth' being marked in any horoscope is because it's always from the Earth that the effect of other planets are deduced. If of course one wants to know the position of Earth, it would be located exactly 180 degrees from the Sun's position in a particular horoscope.
Reference Centric Models
There are different theories and models circulated for estimating the position of planets from a particular reference point. Lets briefly look at the different reference centric models
- Geocentric Model
This is an Earth centric model. As per this model, it is assumed that earth is at the center of the universe and all the planets including the Sun revolve around it. In this model, geo centric positions are calculated with respect to the center of the earth. Geo is alternatively used as a term to describe Earth.
This is an Earth centric model. As per this model, it is assumed that earth is at the center of the universe and all the planets including the Sun revolve around it. In this model, geo centric positions are calculated with respect to the center of the earth. Geo is alternatively used as a term to describe Earth.
- Topocentric Model
This is an Earth centric model. In this model also, it is assumed that earth is at the center of the universe and all the planets including the Sun revolves around it. However in this model, the positions of planets including Sun are calculated with respect to the observers location which can be the actual place of birth of an individual or at the epicentre of where an event has taken place.
- Heliocentric Model
This is a Sun centric model. In this model, it is assumed that the Sun is at the center of the universe and all the other planets including the Earth revolves around it. Helios is another name for Sun and hence appropriately named so.
- Planetocentric Model
This is a planet centric model. In this model, a particular planet is assumed as the reference point with other planets including the Earth and Sun revolving around it. This is mostly adopted with the planet Mars being the source of reference and deducing the position of all other planets including Sun and Earth.
- Barycentric Model
This is a solar system centric model. Barycenter is defined as the center of a mass. In this model, a point in the solar system is considered as the reference and establishes the coordinates of all the other planets including Sun and Earth.
There has been a perennial debate whether its the Earth that revolves around the Sun or whether it's the Sun that revolves around the Earth. Astronomers after numerous research and evidence have finally concluded that it's the latter which holds true. Hence the real picture that takes place in the skies is the Heliocentric model where all planets including the Earth revolves around the Sun.
However we cannot overlook the fact that human beings are born on earth and major events take place on Earth. So it is prudent and makes extra sense to view it with reference to the point of view of Earth. Planetocentric and Barycentric models are basically documented for academic purposes and Heliocentric though it accounts for the real perspective of keeping Sun at the center, it doesn't hold ground at least from an horoscopic angle as all things concerned are looked at with respect to the Earth as the base point.
Thus, while looking at it from a horoscope standpoint, it is the Geocentric or Topocentric model which is used when computing planetary coordinates. In all the astrology software's and even almanacs, it is the Geocentric position that is used at vogue which is the methodology of accounting for planetary coordinates keeping the center of the Earth as the base point. The center of the Earth falls at the Royal Observatory in Greenwich, United Kingdom which falls at a longitude of 0 degrees. Greenwich was universally chosen to be the Prime Meridien of the World in 1884. The Royal Observatory is the source of the Prime Meridian of the world with Longitude of 0° 0' 0''. The prime meridian marks the divide between the eastern and western hemispheres.
Thus irrespective of where one takes birth whether it happens to be east of Greenwich say India or the western side of Greenwich say United States, planetary coordinates will not differ as they are all determined using Greenwich as the central reference point. However there is one important position in a horoscope which is used as the starting reference point known as the Ascendant and this is obtained as the point that is rising on the eastern horizon based on the observers location. Hence lets say person A was born in India at 3PM and person B is born in the United States also at 3PM. Though the planetary positions will remain more or less the same as in both cases as they are determined using Greenwich as the central location, however the Ascendant will undergo a change as the point rising in the Eastern horizon in India will be different from that of the United States. The House counting system is usually done by taking the Ascendant as the base and this will have a major say in the referencing of a Horoscope.
Also one of the major basis for the Geocentric system is that all planetary positions need to be calculated based on a fixed reference point on Earth and it's center position happens to be the only fixed point on the Earth's surface. If we take any other point based on observer's location, it cannot hold to be a fixed common point as the Earth's surface is always moving due to it's rotational movement around it's axis. Planetary coordinates don't really change taking either of Geocentric or Topocentric positions sans the Moon alone. In the case of the Moon, there tends to be a difference by about a degree and this can change the outcome of a horoscope in a major way. The deviation tends to be maximum when Moon is placed near to the Ascendant or in the opposite 7th house and is minimum when positioned near to the 4th or 10th house. Moon's position is especially used while computing Dasa Balance at birth and this could alter proceedings in a major way. However the general norm is that Moon's position is also calculated based on Geocentric position since Moon revolves around the center of the Earth and not just any point on the Earth's surface. However this point should be kept in mind in determining the analysis of a horoscope since it can end up having quite a major impact.
When it comes to determining the Ascendant, it is important to reference the latitude and longitude of the place on earth where an individual is born or an event has taken place. The Latitude and Longitudes combine to form grids which are key for locating places on the earth and arriving at the coordinate position. These are certain imaginary lines drawn on the earth that enables to precisely decode selective places located on planet Earth. The Earth as such is defined as a 'Geoid' meaning that it is slightly flattened at the North & South pole and bulged in the middle. This makes the earth's equatorial diameter as 12756 kms (West to East) whereas it's polar diameter is 12714 kms (North to South). Let's look at a few important snippets with respect to the imaginary lines that are drawn on the earth namely the Latitude and Longitude.
Latitudes:
- Latitudes also called 'Parallels' are horizontal lines that run from the West to the East across the Earth
- The most important Latitude line is the Equator which divides the Earth equally into two halves viz the Northern Hemisphere and the Southern Hemisphere
- The Northern most point of the Earth is termed as the North Pole and the Southern most point of the Earth is called as the South Pole. The lines drawn above the equator are called North Latitudes and lines below the equator are called South Latitudes. It should however be noted that the Latitude lines are not of equal length.
- Latitudes measure the distances in degrees starting with the equator at 0 degrees. They go up the equator marked from 1 to 90 degrees all the way to the North Pole and likewise go down the equator marked from -1 to -90 degrees all the way to the South Pole. The numbers in positive indicate that they are part of the Northern Hemisphere and the numbers in negative indicate they belong to the Southern Hemisphere. Alternatively they can also be coded with the acronym as North and South. Eg +30 degrees in North can be written as 30°N and -30 degrees in South can be denoted as 30°S.
- The other important Latitude lines are the Tropic of Cancer & Arctic Circle located in the Northern Hemisphere and the Tropic of Capricorn & Antarctic Circle located in the Southern Hemisphere. These help to define climatic zones based on the different quotients of sunlight received throughout the year. The Tropic of Cancer is at 23° 26' N and the Arctic Circle is at 66° 34' N whereas the Tropic of Capricorn is at 23° 26' S and the Arctic Circle is at 66° 34' S. Generally they are stated as being 23 and a half and 66 and a half degrees North and South respectively.
- The portion from Equator to Tropic of Cancer in the Northern Hemisphere and Equator to Tropic of Capricorn in the Southern Hemisphere are called 'Torrid Zones'. This is the place where maximum sunlight gets received. The portion from the Tropic of Cancer to Arctic Circle in Northern Hemisphere and from Tropic of Capricorn to Antarctic Circle in Southern Hemisphere are termed 'Temperate Zones'.They are of moderate climate and experience 4 different seasons. The portion from Arctic Circle to the North Pole in Northern Hemisphere and between the Antarctic Circle to the South Pole in Southern Hemisphere is known as the 'Frigid Zone'. These usually experience cold climate as they are placed in an angle that receives very less sunlight.
Longitudes:
- Longitudes also called 'Meridians' are vertical lines that run from the North to the South across the Earth
- The most important Longitude line is the Prime Meridian which divides the Earth equally into two halves viz the Western Hemisphere and the Eastern Hemisphere
- Longitudes measure the distances in degrees starting with the Prime Meridien at 0 degrees. The lines to the right of the Prime Meridian are marked from 1 to 180 degrees all the way to the East and the lines to the left of the Prime Meridian are marked from -1 to -180 degrees all the way to the West. The numbers in positive indicate that they are part of the Eastern Hemisphere and the numbers in negative indicate they belong to the Western Hemisphere. Alternatively they can also be coded with the acronym as East and West. Eg +120 degrees in East can be written as 120°E and -120 degrees in West can be denoted as 120°W.
- The lines of the Longitude help in determining time zones across the globe because when it's day in one of the hemispheres, it's night in the other hemisphere and vice versa. It should however be noted that unlike Latitude lines, Longitude lines happen to be of equal length.
- The 0° longitude which passes through Greenwich is considered as the historic Prime Meridian of the World and all the time zones across the globe are calculated with reference to this. The 180° longitude line to the West and East of the Prime Meridien is termed as the Anti Meridian or the International Date Line.
- The Earth rotates 360° in about 24 hours which equates to 15° for every hour and 1° for every 4 minutes. Hence if time at Greenwich is 12 noon, a place that is 15° to the East would be one hour ahead which would equate to 1PM and a place that is 15° to the West would be one hour behind which would be 11AM. This is also the basis for AM and PM which translates as Ante Meridiem and Post Meridiem where AM refers to before midday and PM identifies with after midday. Thus the A.M (or morning time) is the time before the sun passed meridian and P.M (or afternoon time) is the time after the sun has passed meridian at noon
- Based on the lines of longitude , 24 of them have been marked as standard meridians. Taking Prime Meridian as 0° longitude, the longitudes at 15° intervals are known as Standard Meridians. Hence on the East of the Prime Meridian there are 12 time zones and on the West of the Prime Meridian there are another 12 time zones (180° divided by 15° standard)
Time is decided according to movement of the Earth. Based on this different places have day and night occurring at varying time periods. If there were no time zones prevalent and if every place adopted the same universal time, it would be 6AM in one part of the world and fully Sunny and yet be 6AM in another part of the world and be completely dark. It is usually perceived that the dawn of Sun to be a signifier of morning activities and accordingly Sunrise time is adopted as the morning time in different places and the setting of Sun is considered as evening time in different places. As the Earth rotates from West to East, the places East of the Prime Meridien are those that receive the light of the Sun first and those places to the West of the Prime Meridien receive the light much later on. That is the reason you would see places like Australia, New Zealand, Japan etc gaining time compared to places in the United States, Canada etc which are losing time.
Though there are countries with places which are spread across different standard meridians, it's not always the case that different places within a country adopt different time zones. One example being India which universally adopts a Standard Meridian of 82°30' East based on the Meridian line which passes through Prayagraj in Uttar Pradesh giving rise to Indian Standard Time being 5 and half hours or 330 minutes ahead of Greenwich (82 degrees*4 minutes per degree + 0.5 degrees*4 minutes per degree =328 + 2 = 330 minutes). Thus time in every place in India will be the same irrespective of whether it's in the West or East of India. India also doesn't adopt the concept of Day Light Savings Time which is the practise of advancing clock time during the warmer months so that darkness falls at a later clock time. There are however countries like USA, Russia etc who make use of different time zones and also rake in the concept of day light savings time.
However from an Ascendant calculation point of view, it is important to know the Longitude and Latitude of a place as it is determined based on the degree which is rising in the eastern horizon. Taking India as an illustration, every place in India will have a latitude in the North since it is located above the equator in the Northern Hemisphere and likewise every place will have a longitude in the East as it is located towards the right side of the Prime Meridien. For instance, the recorded time maybe the same in both Mumbai & Chennai at any point of time but the Sun rises much earlier in Chennai being in the South of India which is located at about 80° East of the Prime Meridian as compared to a Mumbai which is placed in the West of India at about 72° East of the Prime Meridian. Hence this needs to be factored in the determination of Ascendant. Also when it comes to accuracy and precision, knowing the exact longitude and latitude of the place of birth of an individual or occurrence of an event also could have a bearing. For instance every nook and corner within a locality may not be of the same latitude and longitude but in many cases we tend to denote an entire city as having the same coordinates. This could lead to some minor discrepancy when determining the exact degree of the Ascendant. For instance an area like Mylapore in Chennai may have coordinated at a slight alteration to the general coordinate which is adopted for Chennai. It would be ideal and more precise if these little matters also be taken care of in order to attain more pin point precision.
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