Uttara Kalamrita : Section IV Sloka 3(a): RajYoga (Auspicious Yoga)

The Yoga describes the good effects of relationship between 9th and 10th Lords

1) 9th Lord in 9th house and 10th Lord in 10th house (own houses)
2) 9th Lord in 10th House, 10th Lord in 9th House (Interchange)
3) 9th Lord and 10th Lord in either the 9th house or 10th house together
4) 9th Lord and 10th Lord Aspecting each other
5) If the 9th, 10th Lords are in conjunction with 1st, 4th, 5th, 7th house lords
6) If 9th , 10th Lords occupy 1st, 4th, 5th, 7th Houses

The above yogas bring wealth and hapiness to the native provided the 9th Lord or 10th Lord are not the lords of 8th or 11th House as well.

Here four type of relationship mentioned elsewhere in classical texts are important. For predictions the strength of the planets, houses and the strength of the relationship is important.

The following are listed in the decreasing order of strength, hence Interchange is the strongest yoga.

1) Interchange
2) Mutual Aspect
3) Lord of the Rasi aspecting a planet in its Rasi
4) Posited Together

Explanation: The 10th being the strongest kendra and 9th being the strongest trikona, the relationship of these two lords is auspicious in these houses.

Houses 1,4,7 being Kendra Houes are considered good for placement of 9th, 10th Lord, and bring auspicious results.
House 5 being the other Trikona house is also a good placement for 9th /10th Lord.

8th and 11th houses being inauspicious houses will result in nullification of the good results if the 9th and 10th lords are also lords of these inauspicious houses.

Impact:
1) Aries Lagna: 9th Lord: Jupiter, 10th Lord Saturn (Also 11th Lord hence ruled out)
2) Taurus Lagna: 9th Lord and 10th Lord Saturn
3) Gemini Lagna: 9th Lord: Saturn(also 8th lord hence ruled out), 10th Lord: Jupiter
4) Cancer Lagna: 9th Lord: Jupiter, 10th Lord: Mars
5) Leo Lagna: 9th Lord: Mars, 10th Lord: Venus
6) Virgo Lagna: 9th Lord: Venus, 10th Lord: Mercury
7) Libra: 9th Lord: Mercury, 10th Lord: Moon
8) Scorpio:9th Lord: Moon, 10th Lord: Sun
9) Saggitarius:9th Lord: Sun, 10th Lord: Mercury
10) Capricorn: 9th Lord: Mercury, 10th Lord: Venus
11) Aquarius:9th Lord: venus, 10th Lord: Mars
12) Pisces: 9th Lord: Mars, 10th Lord: Jupiter

Places where Jupiter, Mars, Venus, Mercury are involved in Yoga: 4

Places where Sun and Moon involved in Yoga: 2

Places where Saturn involved in Yoga : 2

Note: This indicates Saturn is only in the above auspicious yogas for all lagnas only once for Taurus Lagna (Both 9th and 10th Lord)