1st House in Vedic Astrology
Bhava 1, Tanu, is the body and the Lagna, the sign rising at your birth, where the exact time matters a great deal.
Tanu, the body: that is the name of bhava 1, the first house of the Vedic chart. It is identified with the Lagna, the sign that was rising over the horizon at the exact time and place of your birth. A sign takes nearly two hours to rise, and a degree about four minutes, varying with latitude. That is why a precise birth time weighs so much.
The house speaks of your build and presence, your vitality, the temperament you were born with, and the way you move through joys and sorrows. Surya is its significator. It is both an angle and a trine, which gives its lord a special standing. Guru and Budha find their directional strength there, and the Lagna is held to be robust when the Lagna lord, or one of these two grahas, sits in it or aspects it.
As for dividing the houses, you can proceed in two ways. You can count by whole signs, starting from the Lagna: one sign per house. You can also calculate bhavas of unequal width according to latitude, with their midpoint as the most powerful spot. Both ways coexist.
Finally, you can read this same house from the sign of Chandra. There are even special Lagnas, for which the chart is recast each time.
The axis of the 1st house
When Rahu occupies the first house, the bhava 1 that holds the lagna, two readings compete, each keeping a different trait. For some, it means strength. For others, a hard character, hardly touched by compassion, at least in the general case. These latter foresee two gentler cases: a benefic aspecting Rahu, or the node sitting in the sign of the Sun. Then life is described as more comfortable. Ketu sits right opposite in the seventh house, bhava 7, and it is linked with the consideration you expect without those around you returning it.
The two lunar nodes always face each other. Yet each is read on its own, house after house, and the houses are counted in whole signs from the sidereal lagna.