In Jyotiṣa or Indian astrology, the term Upagrāha (Sanskrit: उपग्रह) refers to the so-called "shadow planets" (Sanskrit: छायाग्राह, chāyāgrāha) that are actually mathematical points, that are used for astrological evaluation. Upagrāha is a generic term used for two distinct and different calculations. One type of Upagrāha called Aprakāśa (अप्रकाश) is calculated from the degree of the Sun. Another type is more generally called Upagrāha or Kālavelā (कालवेला) is calculated by dividing duration of diurnal sky (from sunrise to sunset) or the duration of the nocturnal sky (from sunset to sunrise) into eight parts. The classic writers like Parāśara, Varāhamihira and later writers like Vankatesa Śarma, author of Sarvartha Chintamani, all classify the Upagrāhas in various ways. Overview The Vedic astrology is primarily based on the calculation of mathematical points. For instance, the Yoga, also referred to as the fifth part of Panchangam, is the sum of the combined longitudes of the Sun and Moon. Specifically, Upagraha is based on the longitude of the Sun so that astrological insights involving it needs the calculation of the sun's path in relation to other planets. For example, Rāhu and Ketu are determined according to the intersection of the sun and moon's paths in the sky. This serves a number of purposes and one of the most important of these is the determination of the power wielded by the upagraha to provide benefit or harm. For example, an upagrāha's interaction with Dhūma will result in excessive heat, risks of fire, and mental anguish. Mantreśvara in the 25th chapter of his Phaladīpika deals with the nine traditional upagrāhas; the nine upagrāhas are – Māndi (मान्दि), Yamakaṇṭaka (यमकण्टक), Ardhaprahāra (अर्द्धप्रहार), Kāla (काल), Dhūma (धूम), Vyatipāta (व्यतीपात), Paridhi (परिधि), Indradhanu (इन्द्रधनु) and Upaketu (उपकेतु). Gopsh Kumar Ojha clarifies that Māndi is Gulika (गुलिक). With the exception of Yamakantaka the rest eight upagrahas are malefics and produce bad results. Yamakantaka is powerful in conferring benefits same as Jupiter but the other eight have evil influences in the bhavas (houses) they are found to occupy. Aprakāśa Upagrāha calculation The resulting calculations will always leave Dhūma in opposition (180°) to Indracāpa and Vyatīpāta in opposition to Pariveṣa. All the Aprakāśa Upagrāhas are always in a fixed distance from the Sun. Kālavelā Upagrāha calculation Daytime 8 part division Nighttime 8 part division Mapping the Kālavelā Upagrāha by Graha The table below shows how the five Kālavelās correlate to five of the