How Chandrashtama is determined
On any day the transit Moon sits in the 8th house for people of one birth sign — an inauspicious “Ashtama Chandra” window for them. Here is how we find the affected janma rashi and nakshatras.
The Moon in the 8th house
The 8th house from the janma (birth) rashi is a sensitive place; when the transit Moon enters it, that day is Chandrashtama (Ashtama Chandra) for those people — a period to avoid new undertakings, travel and important decisions.
On a given day the Moon occupies one rashi, so exactly one janma rashi is in Chandrashtama (two, on days the Moon changes sign). We name that rashi and the birth stars within it.
“When the Moon transits the eighth from the birth sign, the wise defer auspicious acts until it has passed.”
Seven signs back from the Moon
The affected janma rashi is the one whose 8th house the Moon now occupies — i.e. the sign seven back from the Moon’s current sign.
Take the Moon’s sign
The rashi the Moon occupies now, from the true Drik-Ganita Moon longitude.
Count seven signs back
affected janma rashi = the sign 7 back from the Moon’s sign (so the Moon’s sign is its 8th house).
Expand to birth stars
List the janma nakshatra-padas that make up that rashi — a rashi spans exactly 2¼ nakshatras, so the boundary stars carry only their first or last pada.
The window is the Moon’s whole stay in the sign. When the Moon changes sign during the day, the panchang shows two Chandrashtama entries — each with its own affected rashi and the time it applies — because the sign-change time is computed for your city’s sunrise-day.
The texts we stand on
The rules on this page are drawn from the standard muhurta and dharma-nirnaya literature, computed on a modern astronomical foundation.
Muhurta tradition
On the eighth-house Moon and its avoidance for the affected janma rashi.
Drik-Ganita panchang
The true Moon longitude, its rashi and the sign-change time that fix the window.
Computation: true positions from the Swiss Ephemeris, sidereal with the Lahiri (Chitrapaksha) ayanamsa — the standard adopted by the Indian Calendar Reform Committee for the Rashtriya Panchang.
More from the methodology
How Nivas & Shool are determined
Homahuti, Agnivasa, Shivavasa and Kumbha Chakra — the residence and direction indicators, with their exact tithi/nakshatra formulas.
How Anandadi & Tamil Yoga are determined
The 28-fold Anandadi yoga cycle and the Tamil Siddha / Amrita / Marana yoga — how each is counted from the nakshatra and weekday.
How Kari Dina is determined
The five days of the year to avoid for auspicious activities — two after solstitial sankrantis, three on lunar Pratipada days.
How the Mantri Mandala is determined
The ten planetary offices of the Samvatsara — King, Minister, and the lords of crops, rain and wealth — and the solar ingress that fixes each.
How Raksha Bandhan is dated
Shravana Purnima, the afternoon thread-tying, and the Bhadra (Vishti) window that can push the rite to the next morning.
How Pradosh Vrat is dated
The Trayodashi-at-dusk rule, why each occurrence is named Soma/Shani/Bhauma…, and the greater-coverage tie-break.
Today's panchang
See today’s Chandrashtama in your city’s daily panchang.
How Chandrashtama is determined — Frequently Asked Questions
Chandrashtama (Ashtama Chandra) is the period when the transit Moon is in the 8th house from a person’s birth Moon sign — an inauspicious window for those people, when new work, travel and important decisions are traditionally deferred.
Find the janma rashi (or nakshatra) the panchang lists for the day — those born under it have Chandrashtama. It is the sign seven back from the Moon’s current sign, so the Moon sits in that sign’s 8th house.
Because the Moon can change sign during the day. Each Moon-sign has its own affected janma rashi, so the day carries two windows — each shown with the time it applies for your city.
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