First of all, I want to say Happy Birthday to Shri Shani Dev Maharaj as today is “Shani Dev Jayanti.” This is about Shri Shani Dev with a request to Shri Shani Devi that He may bless me at every moment of my life.
Astronomical facts
Saturn is the sixth planet from the Sun and is also the second largest planet, with a radius of 37,366 miles. It is said to have a small core of rock and iron, then a layer of ice and lastly topped by a deep layer of liquid hydrogen.
Saturn is different from other known planets for the rings it has. No planet in this solar system has rings like Saturn does. The rings consist of small pieces of ice and rock, are 62,000 kilometers wide but just 100 meters thick. The rings are actually made of thousands of closely spaced ringlets, looking like a gramophone record disk.
Saturn has 22 known natural satellites, more than any other planet does.
Vedic Astrological view
From the Vedic point of view, the physical Saturn is only a representation of Shani Dev / Shanaischaram (Saturn God). By the movement of the physical Saturn, we understand the intention of Saturn God (Shani) about us. Saturn God is the natural ruler of karma, and to understand our karma, we must first understand Shani.
Shani is one of the three children of Sun and Chaya Devi. From the Vedic texts, we can learn a lot about Shani. Many times the power of his gaze have been mentioned in the classics. We learn that right after Shani was born, his gaze caused Sun's charioteer to fall down and break his thigh; Sun's horses to get blind; and Sun himself caught vitiligo for Shani's powerful gaze on him. They were healed only when Shani moved his gaze away and looked at somewhere else.
This clarifies the power which Shani has in his gaze.
In Jyotish, Shani is considered a very malefic planet. The nine planets are the incarnation of Lord to bestow us the result of our karma - which are the lessons we need to learn. And most of the times, the toughest lessons are taught by Shani. In our school, we always have different teachers for different subjects like Math, Physics, Language etc. Just like that, different planets teach us different kind of lessons, and most of the times the teacher Shani teaches us very painful lessons. This is not something to doubt when we learn from the BPHS that Shani is the natural giver of grief.
In general, Shani is considered the most malefic planet, and the most problematic, painful yogas involve Shani most of the times. When Shani maleficly affect something, he slows the matter down, and causes obstructions and delays in it's fruitfulness. Shani also rules separation, he hurts us by taking things away from us. When we face a painful separation from our parents, spouse, friends or anyone we care for, Shani is always a possibility for that. Ketu also causes separation as he rules non-attachment, but separations and delays are among the main significations of Shani. He's association with Venus / 7th lord causes separation from spouse most of the times. Though the final comment should be made seeing Shani's strength, placement and lordship, as for Taurus and Libra natives Shani is a functional benefic being a Yoga karaka. But even then Shani will not forget to remind his nature sometimes. That is my personal view on this.
Shani is a planet of Tamasic quality. He is a planet of extreme nature. When he favours someone, he gives very favourable effects. Oppositely, when anyone receives his curse, indescribable pain and miseries he or she faces in life. Shani purifies a person by giving immense sorrow and pain, as fire purifies the gold.
Favourable effects of Shani on one's nature include in-depth knowledge, sensibility, wisdom, justice, broadness of mind, honesty, patience, ability to work hard etc. In life, he may give wealth, fortune, long life etc. when auspicious and well placed.
On the other hand, when badly afflicting a person's nature, Shani can make one sadistic, greedy, lazy, dishonest, fearful, irresponsible and even addicted to drugs. Shani causes obstruction, delay, grief, poverty, short life etc. He makes a person totally lonely, helpless and can make one suffer from enmity, theft, lawsuits etc. Shani can also give imprisonment since he rules obstruction, loneliness and grief.
When causing diseases, Shani generally gives chronic diseases as the person suffers for a long time - by this he again shows his nature of slowness and delays.
When badly effecting one's profession, Shani makes one work very hard but does not give the proper reward he deserves. That is why social servants and people who earn their living by physical labour are ruled by Shani. For the same reason Shani rules the Sudras (4th caste) and abodes in filthy places.
For the power of his gaze, Shani has a tremendous afflicting ability by his mere aspects, which he casts on 3rd, 7th and 10th houses from his own position.
Among other planets used in Vedic Astrology, Saturn is the last one counted from Sun's position. That is why Shani Dev rules 'The last' or 'The end' of anything. He is the 'Last Answer' in anything. In our material world, death is the end of everything, and that is why, Shani rules death and longevity issues. He is the natural significator of 8th house in astrology. We know that 8th house deals with sorrows, shock, pains, depressions and also - occult. That is why Shani also deals with Magic, Tantra, Jyotish etc.
Shani was lamed by another son of the Sun, named Yama (God of death) when he hit Shani in his leg. So Shani is always very slow in his movement. One name of Shani, as I already mentioned, is 'Shanaischaram' which means the slow mover. He takes around 2.5 years to pass through a sign, thus he takes around 30 years to complete the travel over the whole zodiac. So he rules slowness and delays; And he teaches us how to tolerate slowness and delays, by patience. He is generally pleased with people having patience.
The great phase (Maha Dasha) of Shani lasts for 19 years. Even than the Maha Dasha, Shani gets the strong hold of a person by his transit over the 12th, 1st and 2nd signs from his or her natal Moon. This is called 'Sade Sati' since it lasts for about 7.5 years.