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Chaos Game

Physics Quiz

News and Updates

Wolfram's Rule 30 Cellular Automaton

Wolfram's Rule 90 Cellular Automaton

Applet: Brachistochrone

Applet: Catenary

Applet: Triangle

Applet: The Educated Monkey

Applet: Sieve for Prime Numbers (Hyperbola)

Applet: Sieve for Prime Numbers (Parabola)

Applet: Free Fall with Air Resistance

Applet: Rainbow Simulation

Applet: Map Projections

Physics and Astronomy on stamps

Applet: Graphical Construction of an Astrolabe

Applet: Maya Tzolkin Calendar

Applet: Astrolab Graphical Construction

Applet: Neper Multiplication

Applet: Genaille-Lucas Division

Applet: Genaille-Lucas Multiplication

Applet: Draw Analemma

Applet: Moon Flight

Applet: Hohmann Transfer Orbit

Applet: Random Walk

Applet: Entropy

Applet: Transit of Venus 2012, June 5/6

Applet: Rise, Transit, and Set of the Sun, Moon, and Planets

Applets: Geometric solution of quadratic equations (4 applets)

Applet: Dürer's Construction of Spirals

Applet: Durer's Construction of a horizontal and a vertical sundial

Applet: Earth View from the Moon (somnium)

Applet: Bright Stars, angular separation

Applet: Venus Transit 2012

Applet: Eccentric Sun Motion

Applet: Gnomon

Applet: Sun and Moon Lozenge

Applet: Sunrise and Sunset

Applet: Sun-Earth Distance

Applet: Astronomical Gearing

Applet: The Earth's Shape

Applet: Circle Inversion (Hollow Earth Simulation)

Applet: Sun Tables

Applet: Declination, and Equation of Time

Applet: Azimuthal Orthographic Sundial Applet

Applet: Foster-Lambert Sundial Applet

Applet: Planet Observer

Jovian Moons

Applet:Limb Darkening of the Sun

Applet:Solar Rotation

Applet:Lunar Libration

Applet: Lunar Distance Navigation

Applet: Daylight Hours Sundial

Applet: Pingre Sundial (multiple gnomons)

Applet: Babylonian, Italian, and Unequal Hours Sundial

Applet: Cone Sundial

Applet: Solstice Daylight

Applet: Bifilar Sundial

Applet: The Sun's Meridian Transit

Overview (applets): Medieval and Renaissance dials and quadrants

Applet: Altitude Sundial
Interactive simulation

Applet: North Finder Sundial
Interactive simulation of a self-aligning dial

Applet: Spider Sundial
Interactive simulation

Applet: Apian Dial
Interactive simulation

Applet: Capuchin Dial
Interactive simulation

Applet: Quadratum Horarium Generale (Regiomontanus Dial)
Interactive simulation

Applet: Gunter's Quadrant
Interactive simulation

Twilight Sky Compass:
Navigation by polarized skylight

Determining the relative orbital radius of Mars:Mars
Observations and computations of the opposition of 2007

Determining the relative radius of the Moon:Mars opposition
Observation of the total lunar eclipse of Feb 2008

Details of the visibility of the bright planets:
phase, elongation, magnitude, illuminated fraction

Astronomy by JavaScript

Sunrise and Sunset Calculator by JavaScript (equations included)

Java Applets

Sundial in a Box

Howard Sun Compass

Planetary Hours Clock

Sidereal Sundial
This horizontal sundial is showing the local sidereal time

Folding a Circle

SunMoon Clock
local solar and lunar time

Selenocentric motion of the sun and the Earth

Standard Solar Model


Solar Terminator
lines of simultaneous sunrise ans sunset
lines of equal solar altitude

Geocentric Planet Motion

Cylinder Sundial Applet

Stereogram Applet

Lagrange Points Applet

Moon Libration Applet

Moon Distance Applet

Pursuing the Sun
A mathematical Astronomy problem

Solar Rotation Applet

How to compute the position of the Moon

New Moon Observer
calculating local conditions for crescent moon sighting

Atmospheric Refraction
and the apparent flattening of the Sun's disc

Eclipse magnitude and obscuration

Solstice Azimuth

Kepler's Applet
Solving Kepler's equation

How to compute the day/night terminator

Sky Map
showing the bright stars and planets of your local sky for any date and time.

Elevation and Azimuth of the Sun

Elevation and Azimuth of the Moon

Sun Azimut at Rise and Set

Feigenbaum Fractal

Planet Applet
The bright planets - Mercury, Venus, Mars, Jupiter, Saturn - as well as the Sun and the Moon (The seven wanderers known to the ancients.), are the subjects of this applet. It provides 6 views: a diagram showing the rise and set times over the year, a view at the local horizon (rectangular and polar), a view of the ecliptic plane, and a sky map and earth map view.
Exercises for exploring solar, lunar, and planetary events are included.

Proper Motion and Precession

Java applet showing the phase and the age of the moon for any date

Moon Motion
This Java applet computes the motion of the moon (true longitude).

Sky Precession

Water Tube Applet
Physics Quiz

Sun & Moon Azimuth at Horizon

Horizontal Sundial - very easy to make

Night Hours
The applet calculates the duration of dark night hours (civil, nautical and astronomical twilight)

Astronomy applets:
Mercury- and Venus Transit Applets
The Phases of the Inferior Planets (Mercury, Venus)
Planet Orbits
Heliocentric and geocentric Planetary Motion
Cosmology Applet
Hubble Applet

My "GeoAstro Applet Collection"

Sunshine Applet (JARS Top Rated)
An interactive Java applet displaying the hours of most intense sunlight and UV radiation for any location and time. The results can be used to help avoid damage to human skin.

Sun and Moon in Polar Coordinates
Watch the points (azimuth angles) of rise and set of the Sun and the Moon on the horizon as the are changing from day to day
Compare the results with the directions found at the Stonehenge Observatory

Solar and Lunar Standstills


New Sun & Earth Applet

Moon Phases for a Year

Moon Phase Applet

Seasons Applet (Diagrams added)

Local Sidereal Time Clock (configurable)

Analemma Sunclock Applet Make your own sundial !

Paper Sundial - very easy to make by folding a sheet of paper

Sun Shadow Applet
This interactive applet displays the shadow of an object (building, wall, tree) for any location, date and time.

Sun Plotter Applet
By this applet you get the (approximate) times of sunrise and sunset from a geometrical construction for any location, date, and time.

Sun & Moon Polar: positions of sun and moon in polar coordinates for any location and time

Daylight Applet
This Java applet displays a diagram with the times of sunrise and sunset and a horizon view. A table of all data can be written to the Java Console

Sunrise & Sunset Table Applet

"Sun, Moon & Earth Applet" JARS TOP 25% Rated
This interactive applet displays the positions of sun and moon for any date, time and location on the horizon, and on an interactive world map with day and night regions. The times of rise and setting, the moon's orbital phase and more data are computed.

"Sun & Earth Applet" (JARS TOP 5 % Rated)
my new interactive applet: showing the position of the sun (elevation and azimuth) for any date, time and location and the day and night regions on a world map.

Day & Night - Applet JARS TOP 25% Rated
shows the day and night regions on a world map

The Date of Easter: Computing it by JavaScript


Solar eclipses and the Saros cycle


How to compute the position of the Sun

How to compute the length of a day

The Moon: orbit and phases

Declination and Equation of Time by JavaScript

Cosmology (Java applet included)

My Astro Sources
Applets, Software, Books, Links

Astronomy by JavaScript:

Observing satellites, my photos of Iridium flares

Atmospheric Phenomena


HTML Intro

JavaScript Examples (for download)

Online Games in JavaScript

My Link-Collection

Last Modified: 2018, Oct 25