Chandrama Manaso Jataha : From His Mind was Born the Moon

Significance of Moon in Jyotish (Vedic Astrology)

Most of the popular astrology columns appearing in daily newspapers, periodicals, TV shows and many websites tend to be based on the position of Sun in one’s horoscope. Therefore, when one says- I am an Aries or my birth-sign is Aries, it basically means that that person's date of birth was between March 21 –April 19. The Sun would be in Aries in his/her horoscope. For Taurus, it would be during April 20-May 20; for Gemini, May 21-June 20 and so on. 
But in jyotish studies,  it is the placement of Moon in one’s horoscope that determines one’s birth-sign. The zodiac sign occupied by Moon in an individual's horoscope, prepared according to jyotish vidya is often called as rasi, rashi, janma rashi, or the birth-sign.
 The amount of attention and significance given to the Moon in a horoscope in jyotish is truly humongous. 
On an individual level, the placement of Moon in one’s horoscope is used to gauge: 
1. Personality traits and Mental makeup. 
2. Relationships (8-fold match-making). 
3. Janma Nakshatra (birth-star). 
4. Mahadasha (progressed horoscope / karmic timeline / good and bad periods). 
5. Vastu (match-making between one’s house and themselves),. among other issues
 
Moon is also used to find out the most suitable name for a person. You are known to the world by a few letters of the language that come together to form a pattern of sound that becomes your identity. Moon helps in recommending the most harmonious sound patterns for you.
In mantra shastra, moon is used to analyze the name of the god whose mantra would help you accomplish worldly desires. For example, Lord Shiva is also known as : Rudra; Linganath; Maheshvara; Nagendra etc.. Not all names of Shiva will help if one is seeking a mantra for material gain; though for bhakti and moksha any of those names would be effective. 

On a collective level, the Indian Calendar is lunar based. Most of the Indian festivals are based on the movement of the Moon. Fasting during some of the lunar dates (tithis) is based on the position of the Moon. Electional astrology (muhurta) that helps one in finding out auspicious nakshatra is based on the placement of Moon. Many of the Ayurveda and yoga's principles are based on the transit of  Moon. The list hence, is endless. 
The effect of the Moon , both on an individual and on a collective level  is evident from the commentaries on Moon in almost all the treatise available on jyotish shastra. 

The Western astrology is Sun based whereas the Indian astrology is Moon based. 
Sun's energies are often termed as fiery, cruel, hot, passionate, aggressive, dominating, ambitious and masculine. Moon however, is known to be soothing, submissive, emotional, peaceful and feminine. 

Sometimes I have thought - on a collective consciousness level, the energies of the Sun influencing the West have made it aim for the field of science, technology, inventions, dominance, power etc.. Moon, on the other hand, may have made the Indian psyche to be content, tolerant, sensitive, embracing, peaceful, religious. If you look at Indian gods, though they might have gotten into great wars, they don't look like muscle-flexing warriors. Most of them have a certain feminine qualities about their roopa (appearance).  This has a deep metaphysical meaning.

In sadhana marg - Sun represents the jnana marg (path of knowledge); Moon represents bhakti (path of love). In sahitya( literature), Sun is prose; Moon is poetry. Sun is the father whereas Moon is the mother.
It is not a question of Western astrology vs Jyotish studies. Western astrology has its own extensive method of interpreting a horoscope.  But, the way jyotish connects man to the cosmos is truly profound and Moon has a paramount role to play in this enigmatic connection.