☼ The pathway of the Navagraha traversing in a Raasi Chakra is divided into 27 parts and is described by 27 Nakshatras.

☼ Each Nakshatra comes under the rule of one of the Navagrahas.

☼ Nakshatras are 27 and the Navagraha are 9. While all the 27 Nakshatras are equally distributed into the 12 Raasis.

☼ Thus each Raasi comprises two and a quarter Nakshatra. Each Nakshatra is assigned to a Graha.

☼ Thus all the 27 Nakshatras are equally assigned to all the (9) Navagraha.

☼ The order of Navagraha ruling its 3 Nakshatras is as follows. This means that the particular Graha owns the three Nakshatra.

☼ Maha Dasas are the periods of Navagrahas for prescribed periods, which governs the individual horoscope for the time period prescribed for the Dasa Period of the Graha. A child may be born at any time - not necessarily right in the beginning of a Nakshatra in a day. A child could be born during the course of a running Nakshatra. By that time part of the running Nakshatra would be gone before the child is actually born and the remaining period of the Nakshatra will have to be spend after the child is born.

☼ Some part of the running Nakshatra is already gone by the time the child is born. The remaining portion of the period of Nakshatra is taken into account in proportion to the over all time period of the Nakshatra on the day's sequence, for arriving at the period of the first Maha Dasa period. A Nakshatra may end another Nakshatra commences - not exactly on the close of the day - but at any time during the course of a day. If a Nakshatra commences somewhere in the middle of a day, it will run across the two successive days and will end sometime in the middle of the next day.

☼ The overall length of time that a Nakshatra is running from its commencement to completion, is called "Aadiyandam Param Nazhigai" in Tamil Astro terminologies. Aaadi means the 'beginning' and Antham means the 'end'. The toal duration of a Nakshatra from its commencement to completion is called as "Aadiantham Parama Naazhigai". When a child is born in the middle of a running Nakshatra, the duration of Nakshatra spent prior to its birth time is not counted. The duration of Nakshatra remaining from the time of birth is taken for calculation in relation to the overall duration of that particular Nakshatra on the particular day(s).

☼ For example, if the overall duration of the Nakshatra is 24 hours and 24 minutes (61 Naazhigai in Tamil calendar) and if the child was born when 15 hours are already gone in the duration of the overall Nakshatra, the child is running the Maha Dasa of the Nakshatra Graha, proportionate to the remaining duration of the the Nakshatra in relation to the overall duration of the Nakshatra. During the Maha Dasa of a Graha (Planet), it will render such benefits, results, happenings, sufferings as the case may be. This will be consistent with several other factors such as;

☼ the characteristics of the Graha, its position in the horoscope; its relationship with the Graha which rules the Nakshatra on which it stands in the Horoscope (while traversing through the pathway of 27 Nakshatras by the birth time);

☼ its relationship with the house and Lord Graha of the house in which it stands for the time-being; its status in relation to the Lagna of the horoscope;

☼ the extent to which it has traversed in the Raasi at the time of birth (which almost determines the strength of the Graha) - and several such other parameters.Each Navagraha's time duration varies from one another. The Maha Dasa Periods of the Navagraga in general and as a whole are as follows:Sooriyan: 6 Years, Chandran: 10 Years, Sevvai (Angaragan): 7 Years, Raahu: 18 Years, Guru (Prahaspathy): 16 Years, Sani: 19 Years, Budhan: 17 years, Kethu: 7 Years and Sukran: 20 Years.The Maha Dasa Period of each Graha is divided into 9 parts, commencing from the part of the Dasa Lord (Dasa Nathan) and ruled by all the Navagraha in sequence of the Dasa Order. This is called the Bukthi period of the Maha Dasa. Each Bukthi Period in each Maha Dasa Period is further divided into 9 parts, which is called the "Anthram".

☼ A further sub-division is also calculated down the Anthram period which is called "Sootchumam". While arriving at basic conclusions, the Astrologers take into account, which Maha Dasa period the Horoscope is running at the point of time and make their predictions, along with other parameters influencing consideration.

☼ In the heppenings in one life-span, the periods of Maha Dasa are vital indicators. The period would render such results as are consistent with the characteristics of the Graha, whose Maha Dasa is running at the particular time period.

☼ This can not be considered in isolation - but should be read with other parameters influencing the respective Horoscope. The Maha Dasa period is an important factor which indicates the line and nature of happenings to an individual during a particular time.

☼ When concluding what kind of effects may take place in the life of an individual during certain Maha Dasa, it should be seen on which Nakshatra the Graha for the Maha Dasa stands in the Horoscope. It should also be seen if the Lord of the Nakshatra on which the Maha Dasa Graha stands is a Subha Graha or Yoga Graha to the Horoscope.

☼ Other considerations about the effect of the Maha Dasa as stated above will then be followed to arrive at a near correct conclusion. There is a general belief that some Maha Dasa good and some Maha Dasas are bad. There is nothing like that. A Maha Dasa by itself can not be good or bad.

☼ What the Lord Graha of the Maha Dasa is to the Horoscope and what is his status in the Horoscope are the factors with which we can conclude whether a Maha Dasa is good or not good for a person. There is nothing like good Maha Dasa or bad Maha Dasa, in general.