According to prevalent definition of Amal Yoga in Vedic astrology; if in a horoscope, there are planets in the 10th house from ascendant or Moon, Amal Yoga is formed in the horoscope. This Yoga can bless the native with good results related to profession, authority, fame, reputation and many other things.
In real practice, Amal Yoga is not seen producing such results when only the aforementioned condition is 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, the planets placed in the tenth house should be benefic in such horoscope. Apart from that, placements of planets in the tenth house from Moon may not form Amal Yoga, in most cases.
Hence only benefic planets placed in the tenth house from ascendant should be considered for the formation of this yoga. Let’s see how this yoga may be formed when planets are placed in the tenth house from Moon. In case Moon is benefic in a horoscope, the planet/planets placed in the tenth house from it are also benefic and Moon as well as such planet/planets are placed in comfortable houses; Adhi Yoga may be formed in the horoscope.
Taking an example, suppose Mars is placed in the tenth house of a horoscope in Aquarius. Taurus rises in the ascendant and Mars is malefic in the horoscope. Hence Amal Yoga may not be formed in the horoscope.
Taking another example, suppose Mars is placed in the tenth house of a horoscope in Aries. Cancer rises in the ascendant and Mars is benefic in the horoscope. Hence Amal Yoga as well as Ruchaka Yoga may be formed in the horoscope.
Once the formation of Amal 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, suppose benefic Jupiter is placed in the tenth house of a horoscope in Gemini, in Capricorn navamsha of Ardra nakshatra. Jupiter is not strong in Gemini and it is debilitated in navamsha. Hence weak yoga may be formed.
Taking another example, suppose benefic Jupiter is placed in the tenth house of a horoscope in Sagittarius, in Cancer navamsha of Moola nakshatra. Jupiter is strong in Sagittarius and it is exalted in navamsha. Hence strong yoga may be formed in this case.
Let’s look at influences of malefic planets on this yoga. Suppose benefic Jupiter is placed in the tenth house of a horoscope in Sagittarius along with malefic Sun and malefic Saturn. Both Sun and Saturn may cause serious damage to Jupiter. Hence the strength of Amal Yoga may reduce a lot. Accordingly, the native may not benefit much from this yoga.
Looking at the running times; when Mahadashas (planetary periods) of malefic planets are in effect; benefic effects of Amal Yoga may reduce. When Mahadashas of benefic planets other than the ones involved in the formation of this yoga are in effect; benefic effects of this yoga may increase. When Mahadashas of the planets involved in the formation of Amal Yoga are in effect; the native may witness maximum benefits through this yoga. For instance; in the recent example, the native may benefit the most during Jupiter Mahadasha.