Siddhantic Udaya and Asta of Planets (Heliacal Risings and Settings)
This phenomenon is also known as Combustion by moderners, although planets do not get burnt because they never actually go near the Sun. If their angular distance from Sun as viewed from the Earth is below a certain limit, planets are said to be Asta or Heliacally Set (or Combust), otherwise they are Udita.
This phenomenonhas great importance in Astrology, but in physical astronomy there is no significance of this phenomenon because planets actually do not go near the Sun and therefore have no PHYSICAL impact of the Sun on account of this phenomenon. In spite of modern science having nothing to do with it, many "modernisers" of Vedic Astrology" are misusing the name of modern science to change the degrees (Kaalaamshas) of Asta, although the original proponents of such modernisation never produced a single horoscope because they had no faith in Astrology. The most notable person in this regard was Late N C Lahiri, who was appointed by Jawaharlal Nehru to mislead Hindus into adopting an unscientific, irreligious and imaginary panchaanga as the National Panchaanga of India. These fellows tampered with many key concepts of Vedic Astrology, and due to backing by secular government of Nehru Ji their wrong views were popularised by media &c. Among other major astrological concepts deliberately distorted by such fellows were Ayanamsha and Udayaasta-kaalaamshas.
Suryasiddhanta is the earliest source of Kaalaamshas. There is a separate chapter on it in Suryasiddhanta, titled Udayaasta-adhikaara. There we find the following Kalaamshas of planets for Udaya and Asta (in degrees) in verses 6-8 :
Saturn = 15
Jupiter = 11
Mars = 17
8 deg setting in West and 8 deg Rising in East when it is retrograde with large disc,,
and 10 deg Setting in East and 10 deg Rising in West.
12 deg setting in West and 12 deg Rising in East when it is retrograde with large disc,
and 14 deg Setting in East and 14 deg Rising in West.
In same chapter of Suryasiddhanta, Udaya-Asta degrees of all Nakshatras and seven extra star-clusters are given, but Moon's heliacal rising and setting are not called Udaya and Asta due to a technical reason : drik-karma correction is added to the average Kaalaamsha of udaya and asta (= 12 deg) of Moon, after which Moon's phenomena are called Moon's Shringonnati instead of Udayasta, and the final degrees are rarely exactly equal to 12 degrees.
The only utility of Udaya-Asta is for determination of certain religious and related phenomena and activities ; modern physical sciences have no use of Heliacal Udaya-Asta.
Lahiri's Udaya and Asta
In the book "Advance Ephemeris' by N C Lahiri, Suryasiddhantic figures are changed to following figures without giving any proof :
Saturn = 12 deg and 18 deg (instead of siddhantic 15)
Jupiter = 9 deg and 13 deg (instead of siddhantic 11)
Mars = 14 deg and 20 deg (instead of siddhantic 17)
Venus = 6 deg and 9 deg (instead of siddhantic 8 and 10)
Mercury = 11 deg and 15 deg (instead of siddhantic 12 and 14)
Defects in Lahiri's Udaya-Asta and related Ideas
It is clear that Lahiri took Suryasiddhantic value as the average value in the case of Superior planets Mars, Jupiter and Saturn, but changed the average values in the case of both Inferior planets Venus and Mercury. Anyone having some knowledge of elementary astronomy will easily notice that Lahiri's values have nothing to do with modern astronomy or mathamatics, and the only purpose was to destroy Vedic Astrology by means of creating confusion and doubts against ancient classics of astrology. For instance, use Google Search to find out "heliacal rising in modern astronomy", and you will find only ancient topics, because heliacal risings or settings have no use in modern astronomy. Lahiri did not explain why Suryasiddhantic values were discarded by him in the case of Venus and Mercury, and if their Suryasiddhantic Kalaamshas were wrong, then were average Suryasiddhantic Kaalaamshas correct in the case of Mars, Jupiter and Saturn ? Did he use observations to find out his values, or did he rely on his Divya Drishti ? **
The basic defect in the viewpoint of Lahiri and persons similar to him is that they regard Astrology and its Astrological-Astronomy as an Observational Science fundamentally deduced from observed positions of physical (i.e., material or sensorily observed) planets, but as a matter of fact this view is unscientific. Modern Science regards sensorily observed data as the only permissible facts, known as **positive facts in modern science, and any discipline not conforming to this basic tenet of positivism is deemed as pseudo-science. Therefore, Astrology is a pseudo-science according to Modern Science, and things like God, Soul, etc also come under pseudo-science. Astrological properties of planets have no relevance in modern science because astrological properties cannot be related to sensorily observed planets. Hence, either keep entire physical science completely separate from astrology and similar supernatural disciplines which come under Divine Knowledge known as Veda, or forget Veda and Vedaangas completely and make your valuable contributions to modern science instead of wasting your energies on Updating Astrology if you have no regard for the supernatural disciplines of rishis.
It is clear from Lahiri's so-called udaya-asta data which are actually his wild imaginations that he changed siddhantic values upto a maximum extent of 3 degrees. When Varaha Mihira wrote in Panchasiddhantikaa that Suryasiddhanta was the best siddhanta and it was given by the Vedic deity Savitaa which is the deity of most important Vedic mantra Gaayatri, should we deduce that Varah Mihira was a fool to have erred by 3 degrees in observing planetary positions ? Or did Varaha Mihira meant that anything given by deities or rishis should not be tampered (or updated) by common mortals ? These modernisers of Jyotisha did greater crime in the field of Ayanaamsha, which is a completely astrological concept and no scientist has anything to do with it : they changed the very definition of Ayanaamsha and a new definition was invented by 19th century officials of East India Company interested in so-called Indology, which is now used by all supporters of Drik ("observed") in Astrology. These Drik astrologers do not ponder over the fact that astrological traits of planets are quite foreign to physical traits of planets. Thus, these Drik Astrologers are following Lahiri who was guilty of Double Standards : they mix a materialistic physics with a spiritual discipline, which is an unscientific venture. It must be remembered that no real scientist has ever wasted his/her time in updating astrology, they devote their energies and talents to modern science.
Updating Astrology in the name of modern science is a venture of those pseudo-scientists like Lahiri who never made any genuine contribution to modern science, and their only qualification was merely obtaining university degrees and then fame gained by means of following the orders of Jawaharlal Nehru who wanted to destroy Hindu Calendar in the name of science. Nehru, Saha and Lahiri invented a National Calendar which is actually neither national nor scientific, it is a mixture of many strange and unrelated things. For stance, it uses Tropical Sun's year, which is the basis of modern Christian Year, as the basis of India's National Calendar. Is Sidereal Astronomy anti-national or unscientific ? There are nine type of Kaala-maanas recognized in Hindu classics, and tropical year has never been recognized among any Indian system. Moreover, is the year based on Shaka era "national" or anti-national"? It is clear that the real intentions of these atheists was to destroy Hinduism. Why Nehru reformed only Hindu Marriage Act and left untouched the mediaeval Islamic laws of marriage which are degrading and harmful for women ? Why Nehru allowed capturing of properties and income of Hindu temples and spared Islamic and Christian institutions ? Why Nehru and his stooges tried to "reform" Hindu Calendar which is basis of Hindu religious festivals and astrology, sparing Islamic calendar ? And what is the rationale behind the superstition that Christian Year is "scientific" and Sidereal Year of Hindus is unscientific ? Sidereal System is based on the assumptions that positions of planets and starts should be measured with reference to relatively fixed things, while Tropical Syatem is based on a false assumption that Equinoxes of Earth's orbit round the Sun should be the Fixed Reference Point for measuring every motion of everything in the universe, although these equinoxes are actually not fixed points and keep on moving. Any idea which is based on mutually incompatible sets of ideologies cannot be called Scientific" ; actually it is dishonesty and having double standards and is therefore fraud if practised deliberately, or schizophenia if done honestly. Lahiri had obtained a degree in Siddhantic Jyotisha also, hence whatever he did was deliberate dishonesty with the sole aim of selling his annual publications to religious and astrological communities of India in the name of serving modern science !! He made no contribution in any field of modern science.
Those who have real interest in deeper ideas of modern science should study Shroedinger, Einstein, etc, which will remove the false assumption that sensorily perceived phenomena are Absolute Facts. According to Einstein's theory, the perceived position of Sun is merely an Apparent Sun, real Sun lying at infinite distance in a perpendicular direction of the solar pseudo-sphere on whose vortex planetary orbits are situated !! And according to Shroedinger's Wave Mechanics (he was a staunch believer in Vedaanta Philosophy) every "sensorily-perceived" thing or phenomenon is actually wave and perceived things are merely sensory hallucinations. Wave presupposes some Medium, and that Medium is the Cosmic Mind. These apparently unscientific ideas are the basic foundations of modern physics. The fundamental problem of modern physics is Unification of Quantum and Wave theories, termed as the cherished Unified Field Theory, for which Quantum and Wave theories must be unified into a single theory, but these two basic theories of Physics negate each other ever since they were born ! There was a Copenhagen School of physicists led by Neils Bohr which argued that there must be a role of superhuman Consciousness due to which any Wave Packet COLLAPSED at certain limits in order to give rise to Quantum, but Einstein opposed the idea of any role of Consciousness element in Physics. But after atom bombs were dropped on Japan as a result of Einstein's letter to Roosevelt requesting manufacturing of atop bombs by USA in order to restraint Hitler, Einstein was changed : he started visiting synagoes (Jewish temples) regularly for begging pardon for his sin in proposing that Atom Bomb should be made, and prayed that God should stop sending more science to the undeserving human race. God listened his prayer, and since then no theoretical progress has been made in modern physical science, all progress is mere technological. Scientists will never be able to find out the so-called Unified Field Theory, because that theory already lies with humans but can be used only by the devout : the siddhantic theory of the Sun-God Savitaa which allows lesser mortals like us to see into the real nature of things through the Eye of Veda known as Jyotisha.