As per Vedic Astrology texts, there are two types of Yajnas / rituals or tasks - the daily ones and the occasional ones. The daily Yajnas / rituals are those which a person accomplishes on a daily basis. In addition, daily prayers to "Your Deity" also come within the purview of the above. While the occasional ones are often done for fulfilling a particular wish. This wish may be as diverse as the desire for having a child, the desire for wealth in times of financial constraints, having a long term romantic affair / stability in a love relationship, success on the business front or getting rid of certain diseases. In this way, the basis for performance of occasional duties may be anything related to a person or collective welfare. In such a situation, a person seeks the help of astrology when the desires are not completely fulfilled.
A learned Astrologer arrives at a decision after collectively analyzing the placement of various planets in a person's Horoscope chart. Accordingly, the Astrology prediction is given and Astrology remedies in the form of Yajnas / rituals are prescribed for fulfilling the particular desire.
The relationship between astrology and Vedic Yajnas / rituals is one and important. This is because the auspicious time cannot be found without the help of astrology whereas Vedic Yajnas / rituals cannot be performed without the help of any auspicious time.