Parallax Correction – One of the basic principles of Vimsottari dasa system in vedic astrology is division of time into Dasa Bhukthi, which is further driven by moon’s placement in a birth chart. Maharishi Parasarar divided and assigned different time periods in a specific order as Maha Dasas across nine different planets used in vedic astrology, considering 120 years as the total life span for a human. These maha dasas are further subdivided into Bhukthis, Antharams and so on (with same ratio of time distribution as used in dasa division).
In vedic astrology, the zodiac band (360 degrees of a circle) consists of twelve constellations from Mesham (Aries) to Meenam (Pisces). This is further divided into 27 Nakshatras/stars. Each successive nakshatra is assigned a Nakshatra Lord (planet) in a specific order, beginning with Ketu (south node). This assignment will yield an equal distance of 13° 20’ per star in zodiac (360° / 27 = 13° 20’). Each Rasi/house consist of 30° distance (360/12 = 30°). The zodiac can be further divided into 3 equal parts / Mandalams of 120° each, with 4 rasis each per Mandalam. The assignment of nakshatra lord to a nakshatra is very similar from Mesham (Aries) to Kadakam (Cancer), Simmam (Leo) to Vrichigam (Scorpio), and from Dhanusu (Sagittarius) to Meenam (Pisces).
When a birth horoscope is cast, the nakshatra degree range in which moon get placed in that chart will be the Janma Nakshatra (birth star) of that person and the corresponding nakshatra lord’s maha dasa will be the beginning dasa for that person. Maha dasas are assumed to have full bearing on the sequence and timeline of different events in a native’s life.
The table below identifies these different starting points that vary based on the Janma Nakshatra of a horoscope. The moon orbits around earth roughly in less than a day and will pass through one Nakshatra distance of 13° 20’ in a lunar day. That’s why it is said that even one day of difference in birth could affect the sequence of life events for two people differently.
Even when two children were born on the same day and under the same Nakshatra, the degree of moon on which they are born will decide the rest of the maha dasa period and this would have impact on the Bhukthi or other sub period calculations. Since moon travels almost one Nakshatra in a day and different nakshatra lords have been assigned different magnitudes of dasa time, difference of moon placement by a degree will have different timing impact for different nakshatras. Except for Ketu and Mars that have same dasa period times, the impact of this 1-degree difference will be varying for rest of the planets. The table below provides the summary of this impact.
The difference in dasa bhukthi periods will be more for two people born on same day of Bharani or Poosam (Pushya) or similar nakshatras compared to the difference in the dasa balance of people born on Karthigai (Krittika) or Asuvini (Ashwini) or similar Nakshatras. If a person’s Janma Nakshatra lord is Sun, the difference in placement of moon by a degree will alter his dasa calendar by 164 days. If someone is born on Nakshatras where Venus in the Nakshatra lord of the Moon, difference of 1-degree can alter dasa balance period by a whooping one and a half years (548 days)!
Most of the chart reading, predictions, and timing of events in vedic astrology are based on the dasa-bhukthi periods. Nakshatra, its Padam (one nakshatra will have 4 Padham/Padas of 3° 20’ distance), navamsa of moon, general predictions for the dasa-bhukthi period, star matching for marriage, dasa-santhi balance and so many other calculations and derivations used in vedic astrology will be impacted by a change of moon’s degree in a horoscope. Lot of people, who believe in vedic astrology assign significant importance to these timing calculations and won’t even attempt at few things, if they find the dasa bhukthi periods to be unfavorable. I am aware of some friends, who procrastinate from taking important decisions in life, based on their faith in the dasa-bhukthi system. Lot of people awaiting to get married, are denied the opportunity to become couples because they had a dasa-santhi problem.
When too many critical decisions are having dependency on moon’s placement in a chart, shouldn’t the calculation of moon’s position be very precise and scientific in the calculations? This article seeks to investigate the accuracy of the existing system of calculations from moon’s perspective.
Current system of calculation:
Date, time and place of birth (Latitude and Longitude) are the 3 data points required to calculate a birth horoscope. Out of these, latitude and longitude are used only to estimate the Lagna point (ascendant), which indicates the point/rasi that is arising on the east horizon at the specific time of birth. All other planetary position calculations are geocentric by design. One may ask what’s the problem here. Let us get a bit deeper into it, to understand the nuances involved.
The fundamental principle used to determine the placement of a planet in a constellation and nakshatra position is the point of view. The 27 Nakshatras, which are located several light years distances are used as a solid background / screen to ensure the 9 planetary positions are correctly measured and placed in the birth horoscope.
To simply put, when we look at a planet in space from one point on the earth, we consider the nakshatra behind the planet to ensure accurate placement of the planet in question. Based on latituide and longitude used, we could also ascertain lagna / ascendant for the specific time and place. This is how birth horoscopes are cast using astrology softwares and Panchang.
The latitude and longitudes are not used beyond calculation of ascendant point. The lagna point indicates the beginning point of a head portion in a horoscope. All other calculations consider geo-center as the point of view. This mathematical method may be suitable to all 6 major planets from the Sun to Saturn, which are very far from the Earth. However, moon presents a special case that worth detailed study.
The moon lies remarkably close to earth compared to other planets used in vedic astrology. Check out the table below. In this table, the average distance of the planets from the Earth, the time taken for light to reach the earth, and the planetary diameter are provided. A close observation will reveal how closer the moon is to us than other planets.
Let us consider you are at point X and looking at a distant object at point Y. If another object comes in between point X and point Y, based on the closeness of the intermediary object to point X vs point Y, the view may appear differently. When the intermediary object in very closer to middle of your eyes, you might see different views and angle of distant object based on which of your eyes are used for viewing These views will be different compared to viewing by both eyes. We call this small difference in viewing as parallax correction.
When we see a nakshatra from the stationary earth (assumed) through the moon at a specific moment from two locations on earth (locations that are on the same latitude and 180 degree apart in terms of longitude), the perspectives of moon and nakshatra from those two points will be slightly different. In one of the places, the moon may appear to the right of the star. When viewed from other location, the moon will appear slightly to the left of the nakshatra behind. From the geo-center, the nakshatra may be exactly behind moon in this case. The reader is suggested to read more about parallax and more specifically moon parallax for more technical details on this. I have also provided my explanation through a diagram below.
The parallax of the moon
Let us look at the image above. In this picture, a view of earth from top of the north pole is provided (topocentric view). Earth is shown on the left side of picture, a Nakshatra is shown on the right with moon placed in the middle (picture not to scale).
In this topocentric view of earth, two points of the earth’s surface, which lie at the same latitude and 180 degrees longitude apart, are denoted by the two points A and B, respectively (red and green pin drops). The geocentric viewpoint at Earth’s surface is marked with point O (yellow colored pin drop).
You need to assume a static earth and an orbiting moon to understand the different perspectives. Let us assume that on geocentric view the nakshatra lies exactly behind moon’s center (orange colored dotted line). However, at the same time, when viewed from point A, the moon would appear to have moved past the nakshatra. If you view moon from point B, the moon would appear to be approaching nakshatra (not crossed yet).
Which view is correct among the three positions we saw? Each position is correct and should be treated differently. While the view from these 3 points are different, in the current system we are calculating the moon position using geo-centric view only. Further the difference between geo-center (point O) vs point of observation (point A or B), higher would be amount of correction that needs to be accounted for in moon’s position in a birth chart.
Quantum of impact:
It has been estimated that this lunar parallax correction that needs to be applied for moon’s position can range up to ± 1 degree (max of 2-degree difference between point A and B). If your janma nakshatra lord is one among Sukran (Venus), Sani (Saturn), Rahu (north node), Bhudhan (Mercury) or Guru (Jupiter), then this parallax correction can have a significant shift in your existing dasa-bhukthi-antharam calculations.
How to find if the existing dasa-bhukthi calculations are correct in a chart (Courtesy: Das Goravani)
Please consider following points below and see where does the chart of interest fits.
- In your birth horoscope Bhava chart (not rasi chart), look at the position of moon from Lagna/ascendant. If moon is placed closer to the middle of the 10th or 4th Bhava in your horoscope, then your existing dasa-bhukthi calculations holds good and no correction is required (subject to general accuracy of your software). This is shown by the point O in our image (Mid heaven is denoted by 10th Bhava).
- If moon is in the 1st or 7th bhava of your horoscope, then your moon position is a candidate for correction. Hence, existing dasa bhukthi calculations are likely to change and likely to vary based on the nakshatra lord of moon.
- In your bhava chart, if moon is placed near Lagna (11, 12, 1, 2 and 3rd Bhavas), your existing dasa calculations should be moved forward. Because those dasa period might have started already or even might have ended for you. This is shown by point A on the earth in our image.
- In your bhava chart, if the Moon is near your 7th Bhava (i.e. 5, 6, 7, 8 or 9th Bhavas), your existing dasa bhukthi calculations should be moved backwards as moon has not touched the nakshatra / position within a nakshatra yet. This is shown by point B on the earth in our image.
What to do next as a professional astrologer?
This post is kind of a wake-up call for you. Lunar Parallax correction is one of the highly debated subjects in the western world and generally not accepted by vedic astrologers sticking to traditional calculation methods.
- If you are a professional astrologer and use any commercial vedic astrology software, check if you have an option to include parallax correction for moon, while performing the calculations. If you currently do not have this feature in your software, request your software vendor to include an option to perform this correction. Expect some resistance or ignorance from them. The choice of applying this correction should be given to you and not dictated by your software vendor.
- If you are a traditional astrologer making horoscope charts through Panchang, you may request the publisher of Panchang (Almanac) to include calculations that can help you derive such corrections. It is highly likely that such calculations may not be possible to be made available in Panchang as well.
The calculation to derive lunar parallax corrections should be available somewhere for those, who can search for it seriously. The corrections could be implemented using longitude and latitudes of birth place. It may take some time for this parallax correction feature to become available in mainstream astrology software. Some software already feature this option as well. So, implementing this feature is practically possible.
As far as I know, I have not come across this correction feature in any of the trusted / leading commercial vedic astrology software in vogue in Tamil Nadu and other parts of India. If that is the case, then we can easily assume that other small-time astrology software vendors may not offer this feature at present in India.
When we do not know that something may be wrong in our astrological calculations, then the prediction mistakes coming out of such ignorance may be pardoned. However, sticking to something that has certain known amount of error in its derivation will not constitute good professional ethics and such errors will not be pardoned in the court of god, as these errors are more likely to affect other persons lives.
It is fair for professional astrologer to ask what to do until a solution/fix is made available to you. Below are my suggestions.
- When you read a horoscope, look at placement of moon in the Bhava chart. Please see where that fits with my earlier descriptions and suggested corrections. Assess the need for correction and quantum of impact the correction is likely to create on the existing dasa-balance calculations. When in doubt, you could check with the native about some important life events and validate, if a correction would make more sense.
- For natives born with nakshatra lords having higher duration dasa periods, base your timing predictions considering some approximate corrections. Provide approximate ball-park time estimates for events to begin/happen and do not enforce strict timeline estimates for predictions. Handle this carefully, when horoscope matching is involved. Don’t attach too much of importance to Dasa-sandhi mismatch. You can be approximately correct than being exactly wrong, to make some good things happen. This approach will be good for you as an astrologer and incredibly good for the native of a horoscope.
Thanks for your time. Feel welcome to share your comments below.
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P.S: This article is a translated version of my article in Tamil. As you might have noticed so far, I try to be more original in my contents. However, after I had published my article in Tamil, I came across more content on this topic for the first time (link below). My article has lot of similarities with this one. I want to acknowledge this article and suggest the interested readers to explore this one for some additional content in this topic.