Vedic astrology is believed to be originated in India between 5000 B.C to 8500 B.C. The Surya Siddantha, the ancient book of Indian astronomy was also developed during same period of time. It is always surprising to note the knowledge of ancient Indians and without any scientific tools they were able to find the distant objects, its natures and its influence on human lives.
Indian ancient seers first confirmed the existence of planets and their influence on human life through Divya Drishti. Later, Indian astronomers(Bhaskara, Varahamihra, Aryabhatta) developed mathematical correlations to find distant objects. Varahamihra developed Surya Siddhanta that becomes the pioneer text of Indian astronomy. The below answer is a bit philosophical concept, but trust me it will really inspire you.
What are the tool of confirmation
According to Indian philosophy, the confirmation can be done in 3 ways
Katchi pramana - Visual confirmation
Anumana pramana - Confirmation by logics
Agama pramana - Confirmation by seers through Divya Drishti or Yoga katchi
Katchi pramana - Visual confirmation
The visual confirmation may give literal meaning as confirmation through eyes, but visual confirmation actually means that confirmation through sensory organs. Humans have 5 sensory organs viz eyes(seeing), ears(hearing), nose(smelling), tongue (tasting) and body(touching) and we use one or more than one of the sensory organs at a time to confirm the object or a situation. For example, the shape and the color of an object can be confirmed by seeing.
The process of Visual confirmation
We may generally think that our sensory organs will do the confirmation by itself. But the five sensory organs are just an instrument to capture the data and send it to another source to confirm. There are 4 more inner instruments that will help in the process of confirmation. They are
The sensory organs are external instruments and these four(Manas, Buddhi, Cittam and Ahankara) are termed as inner instruments.
The process of visual confirmation
When the sensory organs capture the data(through eyes or ears etc), it will send them to Manas. The Manas is the silo of memory. These memories are from various sources such as Karmic memory(memories from our past birth), evolutionary memory - memory gain through evolution (for ex: calf immediately after birth know how to suck the milk), sensory memory, etc. So the mind will process the data sent by sensory organs and list out the options from its memory. For example, if you see an object(say a table). The sensory organ(in this case eyes) will capture the solid form and will send it to Manas. The Manas will list down the options(table, chair, door etc) from its memory. The buddhi will collect the information from Manas, and it will confirm the object using intellect.
What is the limitation of this process?
This process may look flawless, but there is a huge limitation in this process. The limitation of buddhi is that it will use the intellect according to the ahankara(identity) ie; if you have an identity or belief about something then your intellect will work according to your belief. For example, if you believe in God then your intellect will filter out the information that is supportive to the belief of God.
Secondly, each of these sensory organs has certain limitations. Our eyes can physically see only up to a certain distance, ears can hear the sound with certain frequency. So the visual confirmation is not the best source of confirmation.
Anumana pramana - confirmation by logics
There are certain things that we can confirm through logic. Say if you see lightning then you can confirm that you will hear thunder in few secs. If you see a smoke then you can confirm there was a fire. This logical conclusion will not give correct results in all the situation and hence this confirmation is also not the best source of confirmation.
Who is the true seeker?
The 5 external sensory organs and 4 internal instruments we discussed so far are just instruments, who is the real seeker of the information from the outside world? The answer is Atma or soul.
The soul gets the data from the external world through 5 sensory organs and it is processed and confirmed through 4 internal instruments.
What if the seeker is able to seek without instruments? - Divya Drishti
We just said that the true seeker is the soul and these internal and external sensory organs are just instruments in collecting and processing the data similar to what a computer does it for us.
Our ancient seers with the power of deep meditation were able to directly interact with the universe without the internal and external sensory organs and that is called Divya Drishti. The Divya Drishti don’t have any physical limitation, and hence the soul can visualize the distance objects(planets) and its influence without any internal and external sensory organs.
The distinction of faraway objects
With the power of Divya Drishti, our ancient seers were clearly able to visualize the distant objects including its proximity to Earth. Thus there were able to clearly identify the objects that can influence life on Earth and the objects that have negligible influence in life on Earth. Thus the Indian astrology ignored the distant planet Uranus, Neptune, and Pluto but they included the north and south nodes ie; Rahu and Ketu.