Astrological and Astronomical Terminologies Explained (Detailed)

This document provides a comprehensive overview of key astrological and astronomical terms, ranging from the Solar System's components to specific planetary phenomena and timekeeping methods used in astrological calculations. It includes additional details and examples of calculations where applicable.

1. Solar System & Basic Astronomy

In astrology, the "Solar System" primarily refers to the celestial bodies that are considered "planets" or significant points of influence. While modern astronomy defines planets differently, astrology includes the Sun, Moon, and the classical planets visible to the naked eye, along with two mathematical points (Rahu and Ketu).

Planets (Grahas)

In Vedic astrology, the term "Graha" (planet) is used more broadly than in modern astronomy. It refers to celestial bodies and mathematical points that are believed to exert influence on Earth and its inhabitants. There are nine primary Grahas:

• Sun (Surya): Represents the soul, ego, father, authority, vitality, and general health. Astronomically, it's the star at the center of our solar system. Its position defines the zodiac sign for "Sun sign" astrology.

• Moon (Chandra): Represents the mind, emotions, mother, nurturing, and public perception. Astronomically, it's Earth's natural satellite. The Moon's phase (New Moon, Full Moon) is determined by its angular relationship with the Sun.

• Mars (Mangal): Represents energy, courage, aggression, siblings, property, and drive. Governs ambition and physical strength.

• Mercury (Budha): Represents intellect, communication, logic, education, and business. Influences speech, writing, and analytical skills.

• Jupiter (Brihaspati): Represents wisdom, knowledge, fortune, spirituality, children, and expansion. It is considered the "Great Benefic" and signifies growth and prosperity.

• Venus (Shukra): Represents love, relationships, beauty, luxury, arts, and comforts. It is considered the "Lesser Benefic" and governs harmony and pleasure.

• Saturn (Shani): Represents discipline, hard work, limitations, karma, longevity, and responsibilities. It is often seen as a "malefic" but teaches valuable lessons through challenges and delays.

• Rahu (North Lunar Node): A shadowy planet (mathematical point) representing desires, ambition, illusion, foreign elements, and unconventional paths. It amplifies the qualities of the planet it conjuncts or the house it occupies.

• Ketu (South Lunar Node): A shadowy planet (mathematical point) representing detachment, spirituality, liberation, past life karma, and sudden events. It tends to diminish the qualities of the planet it conjuncts or the house it occupies, leading to a sense of completion or disinterest.

Ecliptic and Zodiac

• Ecliptic: This is the apparent path of the Sun across the celestial sphere over the course of a year, as seen from Earth. It is essentially the projection of Earth's orbital plane onto the celestial sphere. All major planets also orbit close to this plane, so their paths generally stay near the ecliptic. The ecliptic is the fundamental reference plane for astrological calculations of planetary longitudes.

• Zodiac: The zodiac is a band of the celestial sphere extending approximately 8 degrees north or south of the ecliptic, within which the paths of the Sun, Moon, and principal planets are confined. It is divided into 12 equal segments of each, forming the 12 zodiac signs. In Vedic astrology, the sidereal zodiac is used, which is fixed against the background stars, unlike the tropical zodiac used in Western astrology which is based on the vernal equinox.

Signs (Rashis) and Nakshatras

• Signs (Rashis): The 12 zodiac signs (Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces) are $30^{\circ }$ divisions of the zodiac belt. Each sign is associated with specific characteristics, elements (Fire, Earth, Air, Water), modalities (Cardinal, Fixed, Mutable), and ruling planets. They represent different energies and influences that planets express when transiting through them.

  • Aries starts at $0^{\circ }$ of the sidereal zodiac.

• Nakshatras (Lunar Mansions): These are $27$ divisions of the zodiac, each approximately $13^{\circ }20^{\prime }$ in arc. They are based on the Moon's daily movement and represent specific constellations or star groups. Nakshatras are considered more granular and precise than signs in Vedic astrology, providing deeper insights into personality, destiny, and timing of events. Each Nakshatra has its own ruling planet, deity, and characteristics. There are $27$ Nakshatras, starting with Ashwini at $0^{\circ }$ Aries. Each sign contains $2.25$ Nakshatras.

2. Time Concepts

Accurate timekeeping is crucial for astrological calculations, especially for casting precise birth charts (horoscopes).

• Standard Time: This is the uniform time adopted by a country or region, usually based on the mean solar time of a specific meridian (longitude). It helps in coordinating activities across a large geographical area, avoiding the confusion of each locality having its own "local time." For example, Indian Standard Time (IST) is based on the longitude $82.5^{\circ }$ East.

• Local Time (LMT - Local Mean Time): This is the time at a specific geographical location, determined by the Sun's actual position relative to that longitude. When the Sun is directly overhead (culminating) at a particular longitude, it's local noon for that longitude. Local time varies with longitude. For every $1^{\circ }$ of longitude, the local time changes by 4 minutes ($360^{\circ }$ in 24 hours = $15^{\circ }$ in 1 hour = $1^{\circ }$ in 4 minutes).

• Sidereal Time: This is time measured by the apparent motion of the stars, specifically the vernal equinox (the point where the Sun crosses the celestial equator from south to north). One sidereal day is the time it takes for the Earth to complete one rotation relative to the distant stars, which is approximately 23 hours, 56 minutes, and 4 seconds of mean solar time. Sidereal time is essential for astrological calculations as it directly relates to the rising sign (Ascendant) and the positions of houses in a birth chart. The Ascendant is the zodiac sign rising on the eastern horizon at the moment of birth, and it is directly calculated using Local Sidereal Time (LST).

• Greenwich Mean Time (GMT) / Universal Time Coordinated (UTC):

  • GMT: The mean solar time at the Royal Observatory in Greenwich, London ($0^{\circ }$ longitude). Historically, it was the international standard for time.

  • UTC: The primary time standard by which the world regulates clocks and time. It is essentially the modern successor to GMT, though for practical purposes, they are often considered the same. UTC is based on atomic clocks and is more precise than GMT. Astrological software often uses UTC as a reference for time conversions to ensure consistency regardless of the birth location's time zone.

• Time Zones: Regions of the Earth that observe a uniform standard time for legal, commercial, and social purposes. They are typically offset from UTC by a whole number of hours or half-hours (e.g., UTC+5:30 for India, UTC-5 for Eastern Standard Time in North America).

• Time Conversion: The process of converting local time to UTC (or GMT) and vice-versa, or converting between different time zones. This is critical for astrology because birth charts are calculated based on the precise moment of birth, which needs to be converted to a universal time standard before astrological ephemerides (tables of planetary positions) can be used.

  Calculation Example: Time Zone Conversion

  • Scenario 1: Convert Local Time to UTC Suppose you are in Kolkata, India (Time Zone: UTC+5:30). It is 10:00 AM IST on July 22, 2025. To find UTC: $UTC=\text{Local Time}-\text{Time Zone Offset}$ $UTC=10:00\text{ AM}-5\text{ hours }30\text{ minutes}=4:30\text{ AM UTC on July 22, 2025}$
    

  • Scenario 2: Convert UTC to Local Time Suppose it is 1:00 PM UTC on July 22, 2025. You want to find the local time in New York (Time Zone: UTC-4, assuming EDT in summer). To find Local Time: $LocalTime=UTC+\text{Time Zone Offset}$ (Note: for negative offsets, this becomes subtraction) $LocalTime=1:00\text{ PM}-4\text{ hours}=9:00\text{ AM EDT on July 22, 2025}$
    

  Calculation Example: Local Mean Time (LMT) Adjustment

  If a city's longitude is not exactly on the standard time meridian, there's a difference between its LMT and the Standard Time.

  • Formula: $LMT=\text{Standard Time}+(\text{Local Longitude}-\text{Standard Meridian Longitude})\times 4\text{ minutes/degree}$
    

  • Example: Kolkata's longitude is approximately $88.36^{\circ }$ E. Indian Standard Time (IST) is based on $82.5^{\circ }$ E. Difference in longitude = $88.36^{\circ }-82.5^{\circ }=5.86^{\circ }$ East Time difference = $5.86\times 4=23.44$ minutes. So, LMT in Kolkata is approximately 23 minutes and 26 seconds ahead of IST. If it's 10:00 AM IST, it's approximately 10:23 AM LMT in Kolkata.

  Concept of Local Sidereal Time (LST) Calculation

  Calculating LST precisely involves complex astronomical algorithms and reference to a specific epoch (e.g., J2000.0). However, the general principle is:

  $LST=\text{Greenwich Sidereal Time (GST) at 0h UTC}+\text{Time Elapsed from 0h UTC (converted to sidereal hours)}+\text{Longitude (in sidereal hours)}$
  

  • GST at 0h UTC: This value changes daily and is obtained from astronomical almanacs or ephemeris tables.

  • Time Elapsed Conversion: Since a sidereal day is shorter than a solar day, solar time needs to be converted to sidereal time by multiplying by a factor of approximately $1.00273790935$.

  • Longitude Conversion: Convert longitude from degrees to hours ($15^{\circ }=1$ hour). East longitudes are added, West longitudes are subtracted.

  Simplified Example (Conceptual): Let's say on a particular day, GST at 0h UTC is 10:00:00. Birth time is 06:00 AM UTC. Location is $75^{\circ }$ East longitude.

  1. Time Elapsed from 0h UTC: 6 hours.

  2. Convert to Sidereal Time: $6\text{ hours}\times 1.00273790935\approx 6.0164\text{ sidereal hours}$ (or 6 hours 0 minutes 59 seconds).

  3. Longitude in Sidereal Hours: $75^{\circ }\text{ E}/15^{\circ }/\text{hour}=5\text{ hours}$.

  4. LST: $10:00:00({\text{GST}}_0)+06:00:59(\text{converted elapsed time})+05:00:00(\text{longitude})=21:00:59\text{ LST}$.

  This LST value is then used to determine the exact degree of the Ascendant (Lagna) and the cusp of other houses in the birth chart.

3. Daily Phenomena

• Sunrise (Suryodaya): The moment when the upper limb of the Sun appears above the horizon in the morning. Astrologically, this marks the beginning of the day and is a crucial reference point for traditional calculations like Ishtkal.

• Sunset (Suryast): The moment when the upper limb of the Sun disappears below the horizon in the evening. This marks the end of the astrological day.

• Duration of Day and Night (Dinmaan and Ratrimaan):

  • Dinmaan: The duration of daylight, from sunrise to sunset.

  • Ratrimaan: The duration of night, from sunset to the next sunrise. These durations vary significantly throughout the year depending on the latitude and the season. At the equator, day and night are roughly equal (12 hours each). Towards the poles, the variation is extreme. These durations influence the length of various astrological "muhurtas" (auspicious time segments) and the strength of planets ruling day or night.

• Ishtkal: This is the precise time of birth or an event, expressed in terms of the time elapsed from local sunrise. It is a traditional Vedic astrological time unit, calculated by subtracting the time of sunrise from the time of birth/event. It is crucial for determining the Ascendant (Lagna) and house divisions in a birth chart, as the Ascendant changes approximately $1^{\circ }$ every 4 minutes.

  Calculation Example: Ishtkal

  • Scenario: A person is born at 10:30 AM Local Mean Time (LMT) in a location where the local sunrise was at 6:00 AM LMT on the same day.

  • Calculation: $Ishtkal=\text{Time of Birth (LMT)}-\text{Time of Local Sunrise (LMT)}$ $Ishtkal=10:30\text{ AM}-6:00\text{ AM}=4\text{ hours }30\text{ minutes}$
    

  This Ishtkal value (4 hours 30 minutes after sunrise) is then converted into degrees of celestial longitude to determine the Ascendant.

4. Rahu and Ketu & Eclipses

Concept of Rahu and Ketu (Lunar Nodes)

Rahu and Ketu are not physical planets but are mathematical points in space. They are the lunar nodes, specifically the points where the Moon's orbit intersects the ecliptic (the Sun's apparent path).

• Rahu (North Node): The ascending node, where the Moon crosses the ecliptic from south to north.

• Ketu (South Node): The descending node, where the Moon crosses the ecliptic from north to south.

These nodes are always $180^{\circ }$ apart from each other. They move backward (retrograde) through the zodiac at an average rate of about $19^{\circ }20^{\prime }$ per year, completing a full cycle in approximately 18.6 years. In astrology, they are considered powerful "shadow planets" that represent karmic influences, desires, obsessions (Rahu), and liberation, detachment, or past life residue (Ketu). They are crucial for understanding life's purpose and challenges.

Eclipses (Solar and Lunar)

Eclipses occur when the Sun, Earth, and Moon align in a specific way, and the lunar nodes play a direct role in this alignment.

• Solar Eclipse: Occurs when the Moon passes directly between the Sun and Earth, casting a shadow on Earth and obscuring the Sun. This can only happen during a New Moon (when the Sun and Moon are conjunct, i.e., at the same longitude) and when this conjunction occurs very close to one of the lunar nodes (Rahu or Ketu). If the Sun and Moon are exactly at a node, it's a total eclipse.

• Lunar Eclipse: Occurs when the Earth passes directly between the Sun and Moon, casting a shadow on the Moon and making it appear dim or reddish. This can only happen during a Full Moon (when the Sun and Moon are opposite each other, i.e., $180^{\circ }$ apart) and when this opposition occurs very close to one of the lunar nodes. If the Moon is exactly at a node during opposition to the Sun, it's a total lunar eclipse.

In astrology, eclipses are considered significant celestial events that can bring about major shifts, revelations, or karmic events, often related to the houses and planets they affect in a birth chart. Their effects can be felt for several months before and after the actual event.

5. Planetary States in Astrology

Planets are not static; their apparent motion and relationships with other planets or the Sun lead to specific astrological conditions that modify their influence.

• Combustion (Astangata): A planet is said to be "combust" when it is too close to the Sun. When a planet is combust, its natural significations and ability to give results are believed to be weakened or "burnt up" by the Sun's powerful rays. The closer the planet is to the Sun, the more severe the combustion. The exact orb of combustion varies for each planet:

  • Moon: within $12^{\circ }$ of the Sun

  • Mars: within $17^{\circ }$ of the Sun

  • Mercury: within $13^{\circ }$ of the Sun (when direct), or $11^{\circ }$ (when retrograde)

  • Jupiter: within $11^{\circ }$ of the Sun

  • Venus: within $10^{\circ }$ of the Sun (when direct), or $8^{\circ }$ (when retrograde)

  • Saturn: within $15^{\circ }$ of the Sun

  Calculation Example (Combustion): If the Sun is at $10^{\circ }$ Leo and Mercury is at $18^{\circ }$ Leo, the angular distance between them is $18^{\circ }-10^{\circ }=8^{\circ }$. Since $8^{\circ }$ is less than Mercury's $13^{\circ }$ orb of combustion (when direct), Mercury would be considered combust.

• Retrogression (Vakri): This is an optical illusion where a planet appears to move backward in its orbit from Earth's perspective. This happens due to the relative speeds and orbital paths of Earth and the other planet. For example, when Earth "overtakes" an outer planet (like Mars, Jupiter, Saturn) in its orbit, or when an inner planet (Mercury, Venus) passes between Earth and the Sun. The Sun and Moon are never retrograde. Rahu and Ketu are always retrograde. In astrology, a retrograde planet is believed to cause its significations to manifest in an unconventional, introspective, or delayed manner. It often indicates a need to revisit, re-evaluate, or repeat areas of life represented by that planet and the house it occupies. It can also suggest strong past life connections or unresolved karmic issues related to that planet's domain.

  Calculation (Conceptual): Planetary ephemeris tables list the daily longitudes of planets. When a planet's longitude starts decreasing day after day, it is considered retrograde. For example:

  • Day 1: Mars at $15^{\circ }$ Leo

  • Day 2: Mars at $14^{\circ }50^{\prime }$ Leo

  • Day 3: Mars at $14^{\circ }40^{\prime }$ Leo In this sequence, Mars is retrograde because its longitude is decreasing.

• Planetary War (Graha Yuddha): This occurs when two planets (excluding the Sun, Moon, Rahu, and Ketu) are very close to each other in longitude, typically within one degree. In Vedic astrology, the planet with the higher declination (its angular distance north or south of the celestial equator) is generally considered the "victor" in this war, and its significations are enhanced, while the "defeated" planet's significations may suffer. It signifies a conflict of energies between the two planets, impacting the areas they rule in a chart.

  Calculation (Conceptual):

  1. Check Conjunction: Identify if two qualifying planets (Mars, Mercury, Jupiter, Venus, Saturn) are within $1^{\circ }$ of each other in longitude.

     • Example: Jupiter at $20^{\circ }30^{\prime }$ Virgo and Mars at $20^{\circ }00^{\prime }$ Virgo. Their difference is $30^{\prime }$, which is less than $1^{\circ }$, so a planetary war exists.

  2. Compare Declination: Look up the declination of both planets for that specific date and time from an ephemeris. The planet with the greater absolute declination (further North or South from the celestial equator) is considered the winner.

     • Example: If Jupiter's declination is $2^{\circ }$ North and Mars's declination is $1^{\circ }50^{\prime }$ North, Jupiter would be the victor. If Jupiter's declination was $2^{\circ }$ North and Mars's was $2^{\circ }10^{\prime }$ South, Mars would be the victor (as $2^{\circ }10^{\prime }$ is greater than $2^{\circ }$).

I hope this more detailed explanation, along with the calculation examples, enhances your understanding of these astrological and astronomical terms!