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Standard Time or Local Mean Time - Which one is used while casting horoscopes
Let's clear confusion on this basic ingredient for casting horoscopes
Which one is used in casting horoscopes- Standard Time (ST) or Local Mean Time (LMT)? Will the horoscope created using either of them would be significantly different? This short article would be relevant for beginners in learning Astrology. But, it will also make us aware whether Astrologer making our horoscope knows the basics or not.
Converting Standard Time to Local Time
While casting horoscopes, we use Local Mean Time (LMT) only. We convert the Indian Standard Time (IST) or Standard Time (ST) to the Local Mean Time of that place. While casting a horoscope, we first change the ST to LMT based on the latitude and longitude of a location. Earlier we used to do tedious manual calculations while casting horoscopes. But, now, it is effortless as the software does all the calculations in seconds.
Importance of Lagna or Lagnam
We practice the Nirayan Jyotish (फ़लित ज्योतिष) system of Vedic Astorlogy in India. It is different from the Western Astrology system called as the Sayan Jyotish. In Nirayan Jyotish, we give high importance to the concept of Lagna or lagnam. Lagna is the point on the easternmost horizon which rises each day at the time of sunrise.
To calculate Lagna, we need to find the Sidereal Time of that place where the person is born. Sidereal time is crucial to compute lagna. It is the time taken by Earth to make one full rotation around its axis such that a particular fixed star is found at the same place each subsequent day.
During earlier days, there was no concept of a time zone. So, people used to note the time of a local place through shadows in the day time and position of stars in the night time. But, in the current times, there is hardly anyone who sets the watch as per the local time. We all live in the standard time Zones. The clocks/watches today are set according to the respective standard time zones. For instance, India is 5 hrs. 30 mins east of Greenwich Mean Time (GMT).
How do we use this conversion?
Let us say we have a given Indian Standard Time (IST). When we start constructing horoscope, we first take the vernal equinox adjustments. This is 4 minutes for each one degree. Then we calculate the LMT of that place and further calculate the sidereal time. Using the sidereal time, we finally find lagna and longitude cusps of other planets. If we have Local Mean Time of birth instead of IST, we take that local time and proceed to find lagna straight away.
It's LMT only
In a nutshell, while casting horoscopes, we start from IST but convert this to LMT of that place. Then we find sidereal time to calculate lagna and house cusps. In other words, LMT is already taken care of while casting horoscopes. Without converting the Standard Time to the Local Mean Time, we can't make horoscopes. We should never read charts based on standard time, as they would be faulty. Reading such inaccurate horoscopes would not be fruitful.
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