MID CUSP in Vedic Astrology
Besides the bhavas (houses), there are certain mid points in very bhava and these mid points have their own importance. The Nakshatra lord (the Lunar constellations) for that mid point is the key planet for giving the effective results of that bhava.
For example, the midpoint or the mid cusp of the tenth house falls in a particular degree which coincides with some Nakshatra. This Nakshatra is very important as the lord of that Nakshatra holds the key to the bhava and its significance. The Nakshatra Lord of the Mid Cusp is the key planet to give Sukham (Happiness) and called the Sukshadhipati in the Vedic Astrology.
MID CUSP CALCULATION
There are two methods for calculating the Mid Cusp.
1) Earlier theoretically, the Lagnodayam (Ascendant) was taken as the Arambha Sthana (starting point) that Rashi (Zodiac sign). On these lines, Bhavas were divided into thirty degress each. Hence the midpoint of any Bhava would be same as that of the Lagna bhava. Thus one can always draw the mid cusp of every bhava and take out the Nakshatra Lord to know the planet responsible for giving the Karaka (Enabler) of that particular Bhava.
2) Later on or parallel to the above methods, astrologers developed another theory where the Lagnodayam (Ascendant) degree was considered to be the mid cusp or midpoint of the Lagna Bhava (the first house of the horoscope).
On this basis, the degrees that are allocated to each bhava differ. Due to these differences, the mid cusp or midpoint may differ for each particular bhava or segment of a bhava.
In order to get more accurate results or predictions the later principle (second method) was adopted more commonly by astrologers. Under this principle, the Mid cusp point and their lordships is taken by the planet which is represented by the Nakshatra at that point.
It is always advisable that whenever one is trying to analyse a horoscope for any particular Bhava and for diluting or enhancing the results of that bhava, one should always keep in mind the mid cusp of that bhava and the lord of that degree.
One has also to see that planets are not placed in Bhava Sandhi or cusps of the houses. Bhava Sandhi planets tend to lose their characteristic strength in a horoscope though they may be exalted or otherwise powerfully placed.
In order to give maximum benefit to its full potential a planet should be placed in Bhava Madhayama (Center of the house).
Results if planets placed in Bhava Sandhi
Bhava Sandhi planets, if malefic and owner of malefic houses will give good results. Bhava Madhayama represented by lagna lord, benefics may not give the required benefic results. It does not mean that they will not give good results. What is meant here is they are empowered to give best of the results in diluted form. They get hampered in some ways. Due to this, they are in capable of giving their maximum potential results.