Navagrahas do not face each other. They will not see each other. What is the religious reason for this? Any specifics in puranas?
It is only in south India Navagrahas face 8 different direction, with Sun in the middle.
As per Hindu legend, Sage Kalava was suffering from serious ailments along with leprosy. He prayed to the Navagrahas, the nine planet deities. The planets were pleased by his devotion and offered cure to the sage. Brahma, the Hindu god of creation, was angered as he felt that the planets have no powers to provide boons to humans. He cursed the nine planets to suffer from leprosy and were sent down to earth in Vellurukku Vanam, the white wild flower jungle - the modern time Suryanar Kovil. The planets prayed to Shiva to relieve them off the curse. Shiva appeared to them and said that the place belonged to them and they would have to grace the devotees worshipping them from the place. This is the only temple where there are separate shrines for each of the planet deities.
In Bihar a temple of 1910 consist navagrahas in a row. Devotees can have a darshan of navagraha planets in the same side.
- Since Sun is at the center and other eight are around him in eight directions, they have to be placed
NOT facing each other so that people can easily pray to any particular graham/ grahams.
Please read this info: Source - Navagraha placement in a temple and how to worship
In Agama Pradishta, Surya occupies the central place, Chandra on Surya’s east, Budha on his south,
Brihaspati on his west, Shukra on his north, Mangala on his south-east, Shani on his south-west, Rahu on
north-west and Ketu in the north-east. Temples such as Suryanar temple, Tiruvidadaimarudur, Tiruvaiyaru
and Tirucchirappalli follow this system.
In Vaidika Pradishta, Surya is still in the centre, but Shukra is in the east, Mangala in the south, Shani
in the west, Brihaspati in the north, Chandra in the south-east, Rahu in the south-west, Ketu in the north
-west and Budha in the north-east.
Extracted from Navagraha Puranam