title:: Panchang Bachelor Book — Mastering the Calendar tags:: Panchang, Astronomy, Indian Calendar, Book, Intermediate audience:: Intermediate practitioner paired-with:: Panchang Associate Book

Panchang Bachelor Book — Mastering the Calendar

Part I · Deep Foundations

Chapter 1 · Celestial Mechanics Refresher

To truly understand Panchang, we need solid grounding in how celestial bodies move. Let's revisit the key mechanics with more precision.

Earth's Motions

Earth has several simultaneous motions:

The Ecliptic and Obliquity

The ecliptic is the plane of Earth's orbit projected onto the celestial sphere. Earth's axis is tilted 23.44° relative to this plane — this tilt is called the obliquity of the ecliptic.

This tilt causes:

• Seasons: When Northern Hemisphere tilts toward Sun → summer
• Solstices: Maximum tilt toward/away from Sun
• Equinoxes: Sun crosses celestial equator

Chapter 2 · Lunar Motion in Detail

The Moon's motion is more complex than simple circular orbit. Let's examine the key parameters.

Lunar Orbital Parameters

Why Tithis Vary in Length

A Tithi is defined as the time for the Moon's elongation (angular distance from Sun) to increase by 12°. Because both Moon and Sun move, Tithis vary:

Tithi Number = floor((Moon_Longitude - Sun_Longitude) / 12°)

When the difference exceeds 360°, subtract 360° (new month begins).

Chapter 3 · Nakshatras — Technical Framework

Nakshatra Division

The ecliptic is divided into 27 equal segments of 13°20' (13.333°) each:

Pada System (Navamsha)

Each Nakshatra is further divided into 4 padas of 3°20' each. These 108 padas (27 × 4) form the basis of the Navamsha chart in Vedic astrology:

Part II · Calendar Systems In Depth

Chapter 4 · Solar Calendar (Soura Maana) — Technical Details

Tropical vs Sidereal Year

Ayanamsha Calculation

Ayanamsha = Difference between Sayana and Nirayana positions

Nirayana Longitude = Sayana Longitude - Ayanamsha

There are several Ayanamsha values in use:

Indian Solar Months (Rashi-based)

The solar month begins when the Sun enters a new Rashi (Sankranti):

Chapter 5 · Lunar Calendar (Chandra Maana) — Technical Details

Lunar Month Types

There are two ways to define a lunar month:

The 12 Lunar Months

Paksha System

Each lunar month has two Pakshas (fortnights):

Chapter 6 · Panchang — The Five Limbs Calculated

Tithi Calculation (Detailed)

Formula:

Tithi = (Moon_Longitude - Sun_Longitude) / 12°

If result < 0: Add 360°
If result > 360°: Subtract 360°
Tithi Number = floor(result) + 1

Special Tithis:

Yoga Calculation

Formula:

Yoga = (Sun_Longitude + Moon_Longitude) / 13°20'

Yoga Number = floor(result) + 1

There are 27 Yogas, each spanning 13°20' of the combined longitudes.

Karana Calculation

Formula:

Karana = (Moon_Longitude - Sun_Longitude) / 6°

Karana Number = floor(result) + 1

Special Karanas:

Part III · Advanced Applications

Chapter 7 · Festival Calendar — How Dates Are Determined

Indian festivals follow specific Panchang rules:

Find Kartika month (Ashvina Sankranti + 1 lunar month)
Find Krishna Paksha (waning phase after Kartika Poornima)
Find Amavasya tithi (15th of Krishna Paksha)
Check: Moon should not be visible before sunset
Result: October 20, 2026 (approximate)

Chapter 8 · Muhurta — Electional Astrology

Muhurta is the art of choosing auspicious times for activities. Each day is divided into 30 Muhurtas of 48 minutes each.

Inauspicious Periods to Avoid:

Chapter 9 · Advanced Stellarium Techniques

Setting Up for Panchang Study

Step 1: Enable Indian Culture Settings

Step 2: Display Ecliptic Grid

Step 3: Enable Planet Tracking

Step 4: Check Panchang Data

Stellarium shows:

• Current Nakshatra (bottom status bar)
• Moon phase (visual)
• Planetary positions

Useful Stellarium Scripts

Script 1: Track Moon for One Month

// Set location to Delhi
StelMovementMgr.moveToLocation("Delhi", 28.6139, 77.2090, 0, 0);

// Set time to tonight
Core.setTime(Core.getJDfromDate(2026, 7, 2, 19, 0, 0));
// Advance time by 30 days, 1 day at a time
for (var i = 0; i < 30; i++) {
    Core.setTime(Core.getJDay() + 1);
    // Log Moon position
    var moon = StelObjectMgr.getObject("Moon");
    console.log("Day " + (i+1) + ": " + moon.getEnglishName());
}

Script 2: Find Kumbh Mela Alignment

// Set location to Prayagraj
StelMovementMgr.moveToLocation("Prayagraj", 25.4358, 81.8463, 0, 0);

// Search for Jupiter in Aquarius
// Advance time until Jupiter enters Aquarius

Other Panchang Software Deep Dive

Part IV · Practical Exercises

Exercise 1: Calculate Today's Panchang

Instructions:

Exercise 2: Track One Lunar Month

Instructions:

Exercise 3: Determine Festival Dates

Instructions:

Glossary

What You've Learned

• Celestial mechanics: Earth's motions, ecliptic, obliquity
• Lunar orbital parameters and why Tithis vary in length
• Complete Nakshatra system with ruling planets and deities
• Pada system and Navamsha foundation
• Tropical vs Sidereal year and Ayanamsha values
• Detailed Tithi, Yoga, Karana calculations with formulas
• Festival calendar rules and how dates are determined
• Muhurta system and auspicious time selection
• Advanced Stellarium techniques for Panchang study
• Professional Panchang software comparison

Next Steps

You're ready for the Master level! There, you'll learn:

• Historical development of Indian astronomy
• Surya Siddhanta calculations
• Ephemeris reading and interpolation
• Advanced Ayanamsha debates
• Calendar reform discussions
• Research methodology

This book is part of the Panchang series. See also: Panchang Associate Book, Panchang Master Book, Panchang PhD Monograph