According to prevalent definition of Mahabhagya Yoga in Vedic astrology; if a male native is born during daytime and in his horoscope; ascendant, Sun and Moon are all placed in odd signs, Mahabhagya Yoga is formed in the horoscope. Likewise, if a female native is born during nighttime and in her horoscope; ascendant, Sun and Moon are all placed in even signs, Mahabhagya Yoga is formed in the horoscope. This yoga can bless the native with good results related to profession, fortune, authority, fame and a number of other good things.
In real practice, Mahabhagya Yoga is not seen producing such results when only the aforementioned conditions are met. Hence some other conditions should be met in order for this yoga to be formed effectively in a horoscope. Looking at the first condition; both Sun and Moon should be functionally benefic in one such horoscope, for Mahabhagya Yoga to be formed effectively in the horoscope. If one of them is benefic and other one is malefic; weak Yoga may be formed.
Apart from that, the first house should either be vacant or it should be occupied by one or more than one benefic planet. If the first house is occupied by malefic planet/planets; Mahabhagya Yoga may not be formed or it may not do much good; depending on the overall horoscope under consideration.
Taking an example; suppose in the horoscope of a male native (born during daytime), Sun is placed in the sixth house in Gemini and Moon is placed in the first house in Aquarius. Moon is malefic in this horoscope and it afflicts the first house. Hence Mahabhagya Yoga may not be formed. On the contrary; such combination of Sun and Moon may trouble the native a lot.
Taking another example; suppose in the horoscope of a female native (born during nighttime), Sun is placed in the first house in Scorpio and Moon is placed in the ninth house in Cancer. Both Sun and Moon are benefic in this case; and Sun forms Simhasana Yoga which empowers the first house. Hence Mahabhagya Yoga may be formed in this case and the native may benefit a lot from it.
Once the formation of Mahabhagya Yoga is confirmed in a horoscope, the next factor to check is its strength. The strength of this yoga is calculated through the placements of planets involved in its formation in various signs, nakshatras and navamshas; as well as through the influences of other benefic and malefic planets on them. The overall theme of horoscope and running times (Mahadashas) also affect the strength of this Yoga.
Taking an example for male native, suppose benefic exalted Sun is placed in the first house of a horoscope in Aries, in Leo navamsha of Bharani nakshatra; and benefic Moon is placed in the fifth house in Leo, in Taurus navamsha of Magha nakshatra. Sun is strong in its sign of placement as well as in navamsha. Moon may do very well in Taurus navamsha of Magha nakshatra; within Leo. Hence strong Mahabhagya Yoga may be formed in this case.
Looking at the running times; when Mahadashas (planetary periods) of malefic planets are in effect; benefic effects of Mahabhagya Yoga may reduce. When Mahadashas of benefic planets other than Sun and Moon are in effect; benefic effects of this yoga may increase. When Mahadashas of Sun and Moon are in effect; the native may witness maximum benefits through this yoga.