Definitions: Jyotish

Jyotish
from jyoti or light, brillance. Jyotish is the science of light, and considerd the eyes of the veda. In mundane terms it is Indian astrology. At a macro level Jyotish is divided into 3 main catagories or skanda's - Hora or predictive, Ganitha or mathmatical and samhita or signs. That said, there are 6 limbs ( or angas) of these 3 divisions, which are the following:
Jataka - pertains to natal horoscopy and the results or predictions of one's kriya and karma
Gola - astronomy and planetary systems
Nimitta - pertains to signs and omens
Prasna - some call this electional astrology - as charts are cast at the time a question or action takes place
Muhurta - calculation of auspicious times for actions
Ganita - mathmatical calculations defining the movement and postions of the planets in the zodiac

Discussion
Jyotish is considered one of the 6 Vedanga's or extentions of the veda: The 6 are:
Jyotish
Shiksha or phonetics
Chandas or meter
Vyakarna or grammar
Nirikta or etmolgogy (the origin and roots of words)
Kalpa or ritual

Jyotish is different then western astrology as it recognizes a total of 9 graha's (that which binds) or planets. Within the 9 are two nodes as they are called, Rahu and Ketu. Jyotish also recognizes 11 mathmatical points called upagraha's.

What makes Jyotish a wealth of knowledge is its varga chakra's or divisional charts, that indicate various parts of one's life. There are 16 divisional charts outlined by sage Parasara-muni. These varga's or divisions address ones present condition during this life, one's past life matters ( called shashtyamsa or the D60 chart ), one's spiritual pursuits , vimsamsa ( D20), one's relationship with spouse and others ( D9), one's career , the dasmasa chart ( D10), etc. etc.

What is unique to Jyotish, as one looks to higher divisions , they indicate various planes of existence. That is, one's kundali chakra indicates one's physical existence. As you go to other charts, say D13 to D24, the Jyotisha is viewing one's conscious level of existence, then D25 to D36 , the sub-conscious. As one advances within the varga charts, finer levels of existence, past births, etc. are depicted within the chart information.

Another area is various time periods called dasa's. These indicate how creation or the environment may be presented to the native, and how the native may react under these conditions. Two main classifications are recognized. Those of Rasi Dasa systems and those of Lunar Nakshatra's (some call lunar mansions) and are considered graha dasa's. This partition is just one of how the universe presents itself to the native and how one responds. This can be seen as personal , social and/or environmental (that is ,the universe). The most common dasa system is Vimshottari as offered by Parashara muni. This is a 120 year period, owned by Guru ( Jupiter, some call Brihaspiti), yet Parashara outlines 32 types of systems ( see chapt 48, of Brihat Parashara Hora Sastra).

In a nut shell Jyotish recognizes ones merit one has earned ( the laws of cause and effect are universal). The birth chart shows where that merit will manifest, and when. So the chart shows ones "promise, potential and possibility". But where? The 4 areas of life:
Dharma - in ones chart this dharma repeats 3 times; the 1st the 5th and the 9th houses. Dharma is that which upholds.. but upholds what? Right thinking, living, acting, doing i.e. sattvic behavior and is key to a society.
Artha – repeats 3 times 2nd, 6th, 10th houses, and is of wealth matters or the generation and accumulation thereof.
Kama – 3rd, 7th, 11th houses, and the desires of the individual.
Moksha – 4th , 8th and 12th houses. Moksha or Enlightenment has to do with liberation; its interesting to note that the 4th house is here indicating education, which helps with moksha. Also the 12th house, which has to do with sleep, or rest, meditation, helping with moksha. To the trained Jyotisha that is most respectful of the tradition is repsonsible for pointoing out one's Ishtadevata outlined in one's chart and has great delight (and concern) in this area of Moksha and libration of the native.


References used: http://en.wikipedia.org/wiki/Vedanga
Practical Vedic Astrology - G.S. Agarwal
The Spiritual Dimensions of Vedic Astrology - Robert A. Koch
Vedic Astrology - P.V.R. Narashimha Rao
Crux of Vedic Astology - Sanjay Rath
Brihat Parasara Hora Sastra - Maharishi Parasara, commentary by Birish Chand Sharma
Jataka Parijata by Sri Vaidyanatha Dikshita and translated by V. Subramanya Sastri
Upadesa Sutras by Jaimini - translated by Sanjay Rath
Editors note: there are many more books on this, if one has interest, email me and I will make further recommendations.

HDF Posts:
http://www.hindudharmaforums.com/showpost.php?p=8872&postcount=1
http://www.hindudharmaforums.com/showpost.php?p=8886&postcount=1
http://www.hindudharmaforums.com/showpost.php?p=8940&postcount=1
http://www.hindudharmaforums.com/showpost.php?p=8883&postcount=1