Earthshine Explained: Why the Rest of a Crescent Moon Glows
Trace earthshine from Sun to Earth to Moon, compare complementary phases with a worked table, and distinguish illuminated area from observed brightness.
॥ असतो मा सद्गमय ॥
Study Jyotish and Hindu tradition
Thoughtful guides to charts, planets, sacred texts and Hindu traditions. Begin with one subject and go one step at a time.
Panchang and sacred days
37–54 / 72The Moon Illusion: Why the Horizon Moon Looks Bigger
Understand the Moon illusion, compare it with real angular-size changes, and use controlled photos and an original geometry table to test what you see.
Why Is the Moon Visible During the Day? Phases and Daylight Windows
Understand daytime moonlight, waxing afternoon and waning morning patterns, an ideal geometry table and two examples of reading a daylight viewing window.
Why Is the Moon Red or Orange? Horizon Colour vs a Lunar Eclipse
Distinguish an orange horizon Moon from an eclipsed Moon. Follow the two light paths, a simple geometry model and four clearly labelled observation exercises.
Moonrise Direction Explained: Why the Moon Does Not Always Rise Due East
Read Moon azimuth from true north, see how latitude and lunar declination change its rising point, and distinguish ideal geometry from a local prediction.
Moon Transit Explained: Meridian Crossing, Highest Altitude and Zenith
Understand lunar transit with nine latitude examples, a five-position altitude model and a reading checklist. Separate meridian crossing from being overhead.
The Lunar Terminator: Reading Crater Shadows, Moon Phases and Surface Relief
Learn why lunar craters stand out near the terminator. Work through shadow-length examples, projection limits and a practical observation record.
The Saros Eclipse Cycle: 223 Months, Shifting Visibility and a Worked Example
Work through the Saros cycle using three lunar months, original calculations and NASA catalog entries. Learn why similar eclipses need different local visibility checks.
The Metonic Cycle: Why 19 Years Nearly Equal 235 Lunar Months
Understand the 19-year Metonic cycle with worked arithmetic, seven extra months, calendar-date examples and a comparison with Saros eclipse recurrence.
Major and Minor Lunar Standstills: The Moon's 18.6-Year North–South Cycle
Understand lunar standstills with tilt calculations, sixteen horizon examples and a practical observation worksheet. Separate the long cycle from monthly motion.
The Sun's Analemma: Read the Figure-Eight with a Worked Diagram
Understand the Sun's annual analemma with an original calculated plot, twelve monthly examples, equation-of-time signs and a consistent-clock observation worksheet.
Solar Eclipse Magnitude vs Obscuration: What Does 80% Mean?
Distinguish eclipse magnitude from the Sun's covered area with checked circle models, an original graph and worked examples. Read local circumstances without mixing measures.
Zero Shadow Day: When the Sun Reaches the Zenith
Understand Zero Shadow Day through latitude, solar declination, twelve shadow calculations and an original graph explaining two passages, one or none.
Why the Sun Looks Flat at Sunset: Refraction Explained
Explore differential atmospheric refraction with eight solar-disc calculations, nine pressure-temperature examples and an original apparent-height graph.
Venus Phases: Morning Star, Evening Star and Elongation
Understand Venus's phases with a circular-orbit graph, worked distance and illumination tables, and clear distinctions between elongation, size and brightness.
Why Mars Appears Retrograde: Geometry, Stations and a Graph
Derive Mars's apparent backward motion from two moving orbits, with checked examples, a longitude/rate graph and clear limits on model station dates.
Perihelion and Aphelion: Distance, Speed, Sunlight and Seasons
Understand Earth's near and far solar distances with an original ellipse graph, checked speed and sunlight ratios, and unequal-time examples for equal orbital arcs.
Polar Day, Polar Night and Twilight: Why Sunrise Can Be Missing
Explore missing sunrise, midnight Sun and polar twilight with a declared altitude model, nine worked cases, threshold durations and an original graph.