The Moon is considered as a Devata in Hinduism.
It is reckoned as a Planet in Indian Astrology.
Moon rules the mind and is responsible for the soundness of mind.
If the Moon sign is not favorable, one is assailed by doubts,indecision, confusion ans depression.
Moon waxes and wanes.
From the New Moon day(Amavasya), it waxes.
This period of waxing till the Full Moon (Poornima) is called the Shukla Paksha, Shulka means white.
Waning from the Full Moon to New Moon is Krishna Paksha, Krisha mans black
There are 1 5 Days in between Poornima and Amavasya.
Each day, the Moon’s effulgence(Kala) is ruled by a Devi
They are sixteen .
They Kalas are,
The sixteenth Kala is invisible.
Each of these Kalas is ruled by a Devi.
These ae Shodasa(16) Nithyas,
1.Maha Tripura Sundari,
The first one, Maha Tripura Sundari is the Devi Para Shakti herself, and hence the kala ruled by her is not visible to the normal mortals.
In the Sri Chakra these 15 nityas are present in the innermost circle, and the Devi is in the central Bindu.
These 15 Nityas rule the famous 15 letters Devi mantra known as Panchadasakshari Mantra.
Ka E Aie La Hreem Ha Sa Ka Ha La Hreem Sa Ka La Hreem
These 15 Nityas in the form of the 15 Tithis (Phases) have two aspects each – Prakashamsa, which rules the day portion of the Tithi, and Vimarshamsa,
which rules the night part of the Tithi. At night they collect the divine nectar and during the day they release it.
On Poornima or full moon day all the 15 Nityas are in the moon and the moon is shining brightly. On the 1st Thithi after the Poornima, i.e., Pratipada,
one Nitya leaves the moon and goes to the sun and the moon is reduced slightly in size.
This goes on till New Moon.
After Amavasya they return one by one on each Tithi and the moon starts shining again till its full on the Poornima when the last Nitya returns to it.
This is called Shukla Paksha. Kameswari to Chitra are the Nityas ruling the Krishna Paksha Tithis from Pratipada to Amavasya.
In Shukla Paksha the order of the Nityas is reversed, i.e., Chitra to Kameswari.
The Nitya of the Asthami or 8th Tithi, Twarita, is common and constant to both the Pakshas. Hence she adorns the crown of Devi.
The inner triangle of Sri Chakra is known as the Sarva Siddhiprada Chakra and the Nityas are next only to Tripura Sundari in importance.
Kameswari is Goddess Parvati, Vajreswari is Maha Lakshmi and Bhagamalini is Goddess Saraswati.
One Year has 360 days and 360 nights(720)
There are 720 aspects of Devi in a Year.
Each Devi rules 100 Nadis in our body.
Our Body has 72, 000 Nadis.
The Nityas or Eternities of Lalita represent the fifteen lunar days or tithis of the waxing Moon.
Each has her own yantra, mantra, tantra and prayogas or ritual applications.
The full circle of the Nityas also represents the 21,600 breaths a human being takes in a full day and night.
As such, the Nityas are the Kalachakra, or Wheel of Time.
The 15 Nityas are modifications of Lalita with her three gunas and her five elements of aether, air, fire, water and earth.
As the moon remains itself, though appearing differently according to phase, so too does Lalita.
Lalita or Tripurasundari is the 16th day or full moon, with her 15 digits.
Each of the Nityas has a certain number of arms, the totality of arms (= rays) of the whole circle being 108.
Because any unit of time is taken as a microcosm or parallel of any other valid unit, each of the fifteen Nityas thus has 1,440 breaths.
This identity between space, time, Tripurasundari and the individual is elaborated at great length in the Tantraraja Tantra.
The Nityas are the vowels of the Sanskrit alphabet and are identical with both time and space.
For example, if the number of tattvas or consonants (36) are multiplied by the 16 Nityas the number of letters is 576
The multiples of this number provide the number of years in the different Yugas. So the circle of the matrikas and the Nityas is identical with the sidereal zodiac as well as mantra.
This is the primary reason why Poornima Pooja is performed for Devi.
Pooja performed on a Full Moon Day will yield thousand fold effects.