The origin and use of Latitude and Longitude (HD)

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The origin and use of the Horizon System (HD)

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The origin and use of the Equatorial System (HD)

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The origin and use of Latitude and Longitude

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The origin and use of the Horizon System

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The origin and use of the Equatorial System

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The Celestial Sphere

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Earth's Orbital Motion and the Sun's Motion Across the Celestial Sphere

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The Diurnal Motion of the Stars Created by the Rotation of the Earth

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A Simple Demonstration of Parallax

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Stellar Parallax and the Celestial Sphere: Changing Appearance of Constellations From Earth's Motion

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Exaggerated Stellar Parallax: the Apparent Motion of Stars due to Earth's Orbital Motion

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Using a Gnomon's Shadow to track the motion of the Sun

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Seasonal Variation of a Gnomon's Shadow

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Why Solar Eclipses Happen

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Why Solar Eclipses Don't Happen Every Month

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Why Solar Eclipses Happen (redone)

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Why Solar Eclipses Don't Happen Every Month (redone)

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The geometry of solar and lunar eclipses

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The Earth and Moon Orbit Each Other as they Orbit the Sun (not to scale!)

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The Moon's Path around the Sun (object size exaggerated)

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Seasons

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Orbital Elements: Describing an Orbit About the Sun in 3D (HD)

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Orbital Elements: Describing an Orbit About the Sun in 3D

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Tidal Effects on a Planet and Satellite

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Spring and Neap Tides on the Earth

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Ptolemy's Model for a Superior Planet

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Ptolemy's Model for an Inferior Planet

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Copernicus's Model for a Superior Planet

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Copernicus's Model for an Inferior Planet

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Copernicus's Model and the Phases of Venus

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Ptolemy's Model and the Phases of Venus

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Kepler's First Law

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Kepler's Second Law

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Rotation Curve for Our Solar System

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Rotation Curve for a Galaxy and the Wind Up Dilemma

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Density Waves and the Stability of Galactic Spiral Arms (Artist Conception)

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Hypothetical Rotation Curve for a ""Uniform Ball"" of Stars

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A Perspective of Earth's Moon

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Relative Size of the Planets

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A Cloudless Perspective of Venus Based Upon Radar Data

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A Perspective of Mars

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3-D map of Asteroids (astorb.dat from Bowell@Lowell)

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Ringworld Fly-By: Hypothetical Construct of an Arbitrarily Advanced Civilization (large)

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Pulsar: A Spinning Neutron Star with Beamed Radio Emission

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Pulsar: A Spinning Neutron Star with Beamed Radio Emission (revised)

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Pulsar: A Spinning Neutron Star with Beamed Radio Emission (revised and extended)

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Eclipsing Binary

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Eclipsing Binary II

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Spectroscopic Binary

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Anatomy of an Active Galactic Nucleus

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Twisted Magnetic Fields Driving Galactic Jets

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Mass Transfer in a close Binary Star System

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Compact Stars and Gravitational Wells

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Equivalence Principle: Accelerating in Space vs. Remaining Stationary in Gravity

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Equivalence Principle: Stationary in Space vs. Freefall in Gravity

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Expansion of the Universe and Red Shift of Cosmic Background Radiation

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Expansion of the Universe and Wavelength Red Shift

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Hubble's Law: Red Shift/Distance and Cosmological Expansion

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Sending Signals Across Vast Distances and the Expansion of the Universe

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Curvature and the Bending of Geodesic Paths (HD)

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Geodesics and Positive Curvature (HD)

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Geodesics and Negative Curvature (HD)

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Geodesics and Zero Curvature (HD)

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Geodesics and Positive Curvature

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Geodesics and Negative Curvature

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Geodesics and Zero Curvature

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Gravitational Lensing of Light

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Frame Dragging and the Lense-Thirring effect

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Gravitational Wave and Polarization

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Linear Polarized Gravitational Wave

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Elliptically Polarized Gravitational Wave

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Disk Formation in Collapsing Cloud

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