The first nakshatra, Ashwini, starts at Aries 0-00 and ends at Aries 13-30. The next nakshatra, Bharani, starts at Aries 13-20 and ends at Aries 26-40. Then Krittika starts at Aries 26-40 and ends at Taurus 10-00. Then Rohini from Taurus 10-00 to 23-20, and so on, until Revati, which extends from Pisces 16-40 to Aries 0-00.
Two nakshatras take up 26-40, which is 3-20 short of one full sign. 3-20 is 1/4 of a nakshatra, and is called a nakshatra-pada, or simply a pada. As such, Aries contains Ashwini, Bharani, and the 1st pada of Bharani. Taurus contains padas 2-4 of Krittika, Rohini, and the first 2 padas of Mrgasira. Each nakshatra therefore contains 9 padas (note that 3-20 x 9 = 30 degrees, or one full sign).
The notation Ashwini-1 means the 1st pada of Ashwini, Ashwini-2 the 2nd pada, and so on. Aries then contains Ashwini, Bharani, and Krittika-1, and Taurus contains Krittika-2,3,4, Rohini, and Mgrasira-1,2.
Four signs contain 9 x 4 = 36 padas, or 9 full nakshatras. This happens 3 times, as indicated by the breaks in the nakshatra table below. Aries - Cancer contain Ashwini - Ashlesha, Leo - Scorpio contain Magha - Jyeshta, and Sagittarius - Pisces contain Mula - Revati.
Just like the signs, each nakshatra has a ruler or owner. Unlike the signs, Rahu and Ketu are assigned rulerships. Ashwini is ruled by Ketu, Bharani by Venus, Krittika by Sun, then Mars, Rahu, Jupiter, Saturn, and Mercury. The cycle then repeats in the same order two more times. Note the order of nakshatra rulership is the same as the mahadasa order in the vimshottari dasa scheme, as it must be, since this is how the vimshottari dasa order is defined.
A table summarizing the nakshatras is given below.
| Nakshatra | Ruler | Start |
|--------------------|---------|-----------|
| Ashwini | Ketu | Ari 0-00 |
| Bharani | Venus | Ari 13-20 |
| Krittika | Sun | Ari 26-40 |
| Rohini | Moon | Tau 10-00 |
| Mrgasira | Mars | Tau 23-20 |
| Ardra | Rahu | Gem 6-40 |
| Punarvasu | Jupiter | Gem 20-00 |
| Pushya | Saturn | Can 3-20 |
| Ashlesha | Mercury | Can 16-40 |
|--------------------|---------|-----------|
| Magha | Ketu | Leo 0-00 |
| Poorvaphalguni | Venus | Leo 13-20 |
| Uttaraphalguni | Sun | Leo 26-40 |
| Hasta | Moon | Vir 10-00 |
| Chitra | Mars | Vir 23-20 |
| Svati | Rahu | Lib 6-40 |
| Visakha | Jupiter | Lib 20-00 |
| Anuradha | Saturn | Sco 3-20 |
| Jyeshta | Mercury | Sco 16-40 |
|--------------------| --------| ----------|
| Mula | Ketu | Sag 0-00 |
| Poorvashadha | Venus | Sag 13-20 |
| Uttarashadha | Sun | Sag 26-40 |
| Shravana | Moon | Cap 10-00 |
| Dhanishta | Mars | Cap 23-20 |
| Satabisha | Rahu | Aqu 6-40 |
| Poorva Bhadrapada | Jupiter | Aqu 20-00 |
| Uttara Bhadrapada | Saturn | Pis 3-20 |
| Revati | Mercury | Pis 16-40 |
|--------------------| --------| ----------|
The nakshatras act as a filter through which the grahas act. Take Sun at Aries 10-00; this corresponds to Ashwini, which is ruled by Ketu. Sun therefore has an influence from Ketu, and we need to look at the disposition of Ketu to fully understand the influence of Sun. The situation is analogous to wearing sunglasses; it is still a sunny day, but it is now seen through a green filter. The nakshatras are that filter.
We continually emphasize the word graha here and in other articles in this Web site. The hypertext link in the above paragraph explains the reason for this. It is explained there that the word graha means to grasp, or lay hold of. The entity that the grahas are grasping onto are the nakshatras.
When one graha is in a nakshatra ruled by another graha, it acts to integrate the influences of the two grahas. This integration is often important for providing balance. For example, Jupiter is an expansive graha, and this is taken to be "good". On the other hand, too much expansion can result in obesity, or excessive accumulation. Saturn, on the other hand, indicates constriction, and is often considered "bad". When Jupiter and Saturn balance each other it can provide for a very strong foundation which can result in "healthy growth", or growth (expansion) with balance.
For activities with long-term implications (buying a house, starting a new job), Moon should be in Rohini, Uttarashadha, or Uttarabhadrapada, which are the fixed nakshatras.
For travel and pleasure activities, Moon should occupy Ashwini, Pushya, or Hasta; these are called the light nakshatras.
Dhanishta-3, up to and including Revati-3, is considered unsuitable for all auspicious work. As this covers 5 padas, it is called nakshatra panchaka (panch means 5).
Pushya is considered favorable for all auspicious activities, except marriage.
The above rules are general and universal, as they apply to everyone at the same time, since the nakshatra position of Moon does not depend on geographic location. This obviously means that you need to refer to the birth chart to optimize the best times for a given person, based upon the dasas and transits in effect at any given time. We can therefore view the above rules as fixed, and the indications from the birth chart as temporary. This fixed/temporary duality is repeated many times in Jyotish, and is highlighted a number of times in this Web site.