Vedic astrology based marriage match, also called melapak, is one of the most important criteria for Hindu marriages. There are various criteria an astrologer need to look while matching the horoscope. These are some of the important points that needs to be considered in horoscope matching -
Ashtakoot (36 points) or Porutham
Porutham is the term used almost in the same sense in South India as 'Ashtakoot Guna Milap' (36 point match) in North Indian. Generally in south India, it is divided into 10 sub items, whereas in North India, it is divided in 8 items viz. Varna, Vasya, Tara, Yoni, Gana, Nadi, Rashi lord, and Bhakoot. The 36 points match is primarily a matching of Janma Nakshatra (birth constellation) of bride and Janma Nakshatra of groom. Generally Nadi match is considered the most important one followed by Bhakoot match. It is the reason Nadi dosha has given 8 out of 36 points and Bhakoot dosha is given 7 out of 36 points. Especially if there is no nadi matching, the marriage is not regarded good. You can use http://www.astrosage.com/ to figure out your 36 points matching. You can also find a table in most of the popular Hindu panchang and Jantri from where you can find the matching points obtained. Only information you need to have ready is Janma Nakshatra (constellation), as the ashtakoot milan is calculated using Janma Nakshatra only.
Generally there is a misconception that the married life should be good if number of points obtained are good in Ashtakook Guna Milap. We need to understand that ashtakoot guna milap is just for compatibility between husband and wife. It doesn't not tell about the overall quality of the married life. For example, even if there are 36 out of 36 match, but the other factors of marriages are spoiled in the birth chart, the married life will not be good. Some of the very important houses are 2nd (family), 5th (progeny/ child birth), 7th (husband/wife), 8th (sex life), 11 (overall happiness) and should be good in horoscope. Also good position of Venus and Jupiter is very important for happy married life. It is said that the marriage match between Rama and Sita was 36 out of 36 match. Though we all know that their marriage was no cakewalk. On the other side, we know the understanding and compatibility between both of them was excellent and I believe it was due to this 36 point ashtakoot match.
Manglik dosha is another important criteria for marriage matching in Hindu astrology. Manglik Dosha (also called Mangal Dosha) is said to be exist in a birth chart if Mars is 1,4,7,8, and 12th house. Few astrologer suggest to use Lagna Chart (rasi chart), Moon chart, Venus chart and Navamsa chart for checking Mangal dosha. The more time it repeats in one's chart, higher the intensity of mangal . For example, if the dosha exists in all the above mentioned charts, it is considered 'high level' of mangal dosha. If it exists, for example, only in one of the above mentioned charts, it is considered 'low managal' dosha. The exact definition of Mangal dosha is somewhat disputed among astrologers, and that is the reason astrologers apply their own modifications as well. Lack of common creates lots of confusion in general public. One astrologer may tell you that there is mangal dosha and other may tell that it is not there. If we go by above definition of Mangal dosha, almost all the charts have mangal dosha to some extent though the intensity may vary.
I personally consider Mangal dosha only if Mangal (Mars) is malefic in the birth chart based on the Vedic astrology principles. If Mars is well places, even if it is in 1,4,7,8,12, I don't consider it Mangal dosha.
The third one is shadashtak. In other words, the moon sign (rashi) or bride and moon sign or groom should not be 6-8 to each other. The 6-8 placement is called shadashtak and is not considered good for marriage. Few people also consider 2-12 placement as malefic.
How much weightage should be given to each of above criteria is again disputed among astrologers. For example, few astrologers don't pay attention to shadashtak whereas other astrologers believes that the Shadashtak match is very important. Similar case is with Mangal dosha and Ashtakoot Matching.
As as astrologer, I consider another parameter very important which is the individual birth chart. The first thing that an astrologer should judge is the chart from the aspects like family, health, childbirth, and finance perspective. Which of these aspects are important is up to you. If individual chart is not good, in my opinion, even the perfectly matched chart with 36 out of 36 guna doesn't make any sense to me.
1. Manglik Dosha Remedies
2. Free Online Marriage Matching