There are many Chakras in the Antah-Karana and each chakra has a sphere of light. Therefore in Brahmanda the light is not uniform, more at some places and less at some places. At places there are points of light, at places it is in form of flames and at places it has the shape of Diving Visions. In order to make this light glow uniform there are six Richas and twelve Tyachas. These keep on bridging the gaps of light. These constitute an order of particles of light and the Sadhaka can easily reach his goal the point of Brahma Randhra.
The six Richas perform the job of making the light of the first seven chakras uniform, while the twelve Tyachas mix the light of the twelve chakras up to Brahmanda and establish a uniformity in light. Each chakra acts like a step for the attainment of yoga, and itself acts as a complete step. Thus in order to reach the top one has to go step by step.
Each Richa and tycha has its own attributes. These provide sustenance to the Antah-karana and the chita goes on becoming gradually stable for longer periods. The stability of chita bestows the boon of Samadhi and the duration of the practice goes on increasing gradually.
It is by Samadhi alone that each object merges back into its own cause; such a state of unison is termed yoga equalibrium Samrasya. It is therefore concluded that the experience of Brahma is through the knowledge of Samadhi.
Trataka of the Richas and Tyachas should only be done after the practice of external Trataka, other wise full light can not be activated. The following is the practice for external trataka :-
1) To Gaze on a circle or Dot on a wall.
2) To visualize a flame of a burning lamp and keep the gaze steady.
3) To visualize many flames of many burning lamps and then to see them as one.
All these can be easily practised. Gradually increase the time period of the practice. The body must be kept straight. Do nectar drinking when ever necessary.
After the practices of external Trataka the internal Trataka practice is done by making any internal organ as the aim or target. The light becomes uniform as an effect of internal Trataka. The intensity of light is of great magnitude and is uncomparable. This light is utilized for visualizing and contacting the Brahma-Randhra in daily life. Gradually this light decreases in its intensity and is replaced by a pure unblemished glow. It can be compared to the light of the stars litting the sky on a dark Amavasya night. It is neither light nor darkness. It has been designated as Brahma - Prakasha or the light of Brahma.
Nothing is visible here and the chit cease to function therefore an automatic state of Samadhi develops.
For the realization of this light do the practice of Samadhi according to one's convenience. With practice the Samadhi period goes on increasing and at the time of death the Sadhaka is established in his own form or true self and realizes God. There is not the least doubt about it.

Aum Shantih, Shantih, Shantih
The Mother Gayatri and
Yogi Raja the Master