Shani Yantra should be installed and worshipped to appease planet Saturn. As per Ancient Vedic Texts, Saturn is a Cruel planet. Astrologically, Saturn is the Lord of Zodiac sign Capricorn and Aquarius. It is Exalted in zodiac sign Libra and Debilitated in zodiac sign Aries. It is said that planet Saturn is a judge of our past deeds. The planet Saturn is a natural benefactor of jobs and services, metals, industries, age, poverty, hardships, diseases, all kinds of obstacles and selfishness. A person having weak or a malefic Saturn in his horoscope has to undergo sufferings in all his life and his progress is very slow even with a very hard work. However, if the planet Saturn is favourable in a person's horoscope then he can get very good Success, Name and Fame in his Business / Career especially in those areas that are governed by Saturn like industries. When Saturn is adverse, it causes many problems, accidents, conflicts, poor financial position, sorrow, sadness, depression, poverty etc. Under such circumstances, a Shani yantra can bring peace and comfort.
If the planet Saturn is in conjunction with planet Rahu, then it forms a bad yoga known as " Shani Rahu Shrapit Dosha " which adversely affects almost all the areas of life and the person's life is full of hardships. Similarly, if the planet Saturn is in conjunction with planet Moon, then it forms another bad yoga known as "Shani Chandra Vish Yoga". Such a person is very intelligent, yet at times he can fall prey to extreme negativity and depression. In all such cases, worshipping a Shani Yantra can be extremely beneficial.
A person is said to be under the major affliction of Saturn known as "Saturn Sade Sati" when the planet Saturn is transiting through the 12th, 1st and 2nd house from the Natal Chart Moon, each transit being of approximately two and a half years. A person has to undergo all kinds of hardships during this period including stress, anxiety, tensions, loss of mental peace as well as financial losses. These problems are more profound if the planet Saturn is malefic in his horoscope.
Similarly, a person is said to be under the minor affliction of Saturn known as "Small Panoti" when the planet Saturn is transiting through the 4th or 8th house from his Natal Chart Moon. The adverse effects of Small Panoti are also similar to Saturn Sade Sati. In both these afflictions also, establishing and worshipping a Shani Yantra can provide a immense relief by the blessings of Lord Saturn.
