Vedic astrologers are well aware that nothing in the universe is stationary. Therefore it is irrelevant to consider the movements of earth and other heavenly bodies in relation to an arbitrary fixed point, such as the sun. It is far more convenient and practical to simply consider the surface of the earth as the central point, and calculate the motions of the bodies of the universe from their actual observed positions in the sky.
In other words, Vedic astronomy considers the position and movement of all heavenly bodies in relation to the earth. Vedic astronomy and astrology consider the earth as the center, and all other heavenly bodies move around it. Vedic astronomy and astrology are thus geocentric, and not heliocentric (considering the Sun as the reference point) like Western astronomy and astrology.
The Vedic sages certainly were not ignorant of Earths motion around the Sun. Vedic astronomy understands quite well that the Sun is the center of the solar system. But the Earth, the other planets, the Sun and even the Galaxy are all in constant relative motion. From which point do we measure all this movement? We live on the Earth and see the universe from this vantage point; so for Vedic astronomy, the most practical and convenient fixed point is the pole star, currently Polaris or Dhruva-loka in Sanskrit.