Introduction to Astronomy
Observing the sky
Introduction to Astronomy
Observing the sky
Textbook (Chapter 2)
Introduction to Astronomy
Observing the sky
Overview
When we are making observations from Earth -- there are two main systems that we use to identify the locations* of celestial objects. You will learn about both systems in this module.
* As will become clear, both systems locate celestial objects on an imaginary sphere called the Celestial Sphere. Neither system references how far things really are.
is a global coordinate system (in reference to Earth's rotational axis and therefore is a system that is the same for all observers on Earth.)
is a local coordinate system (in reference to the observer's location on Earth, and therefore differs from one location to another.)
The Horizontal system
The Equatorial system
Introduction to Astronomy
Observing the sky
The sky above your head
aka The Local Sky
aka The Horizontal Coordinate System
aka The Altitude-Azimuth (Alt-Az) System
Introduction to Astronomy
Observing the sky
The sky above your head
aka The Local Sky
aka The Horizon Coordinate System
aka The Altitude-Azimuth (Alt-Az) System
Watch this video from Dr. Maria Weber introducing the celestial sphere and the horizontal coordinate system
Introduction to Astronomy
Observing the sky
The sky above your head
aka The Local Sky
aka The Horizon Coordinate System
aka The Altitude-Azimuth (Alt-Az) System
Watch this video to learn the definitions of: horizon; zenith; meridian; altitude; azimuth; local noon
Introduction to Astronomy
Observing the sky
The sky above (star trails)
From your perspective, stars appear to rise and set on a rotating celestial sphere.
Introduction to Astronomy
Observing the sky
The sky above (star trails)
From your perspective, stars appear to rise and set on a rotating celestial sphere.
Introduction to Astronomy
Observing the sky
The sky above (Earth's rotation)
Alternatively, this can be seen as a consequence of the rotation of Earth around its axis.
Introduction to Astronomy
Observing the sky
The sky above (Earth's rotation)
Timelapse video 1
Timelapse video 2
click below to watch
Introduction to Astronomy
Observing the sky
The sky above your head is part of the full sky
Your local sky is a portion of the celestial sphere
Watch this video as many times as you need to!
Introduction to Astronomy
Observing the sky
The sky around us
aka The Equatorial system
aka The RA-Dec System
Introduction to Astronomy
Observing the sky
The sky around us
Introduction to Astronomy
Observing the sky
The Equatorial Coordinate system
Watch this video for quick definitions of: latitude; longitude; declination; right ascension
Introduction to Astronomy
Observing the sky
The sky around us
Watch this video from Dr. Weber for more in-depth explanation of the equatorial coordinate system
Introduction to Astronomy
Observing the sky
The sky around us
Yet another nicely detailed explanation.
Introduction to Astronomy
Observing the sky
A comparison of both systems
A summary of both systems & the difference between them.
Introduction to Astronomy
Observing the sky
A comparison of both systems
Star trails appear in long exposure photography, and show the apparent motion of the stars from the observer's perspective.
Introduction to Astronomy
Observing the sky
Simulating the sky above your head
Introduction to Astronomy
Observing the sky
Constellations & Astrology
Introduction to Astronomy
Observing the sky
Constellations & Astrology
Watch this video to learn the definition and history of constellations
Watch this video from Dr. Weber about the difference between Astrology & Astronomy
Introduction to Astronomy
Observing the sky
Constellations & Astrology
Watch this video from Dr. Weber for more in-depth explanation of the difference between Diurnal motion and annual motion, and how that affects which constellations are visible.
Introduction to Astronomy
Observing the sky
Geocentric vs Heliocentric models
Introduction to Astronomy
Observing the sky
key terms
There were many new terms defined in this module. Click on the down arrow to review / learn more about each term.
Introduction to Astronomy
Observing the sky
key terms
Introduction to Astronomy
Observing the sky
key terms
Introduction to Astronomy
Observing the sky
key terms
Introduction to Astronomy
Observing the sky
key terms
