Download Observational Astronomy Star Charts

Observational Astronomy
Mapping the Heavens
Coordinate Systems
We have two different ways to locate objects in
the sky:
• Celestial equatorial system
-Right Ascension and Declination
• The horizon system
-Altitude and Azimuth
Celestial equatorial system
Celestial Sphere
Celestial Sphere
Observational Astronomy
Locate your Star Charts
SFA Star Charts
• Star Chart 1 - Northern Region
• Star Chart 2 - Equatorial Region
• Star Chart 3 - Equatorial Region
• Star Chart 4 - Southern Region
SFA Star Chart 1
North Star
“Little Dipper”
Declination
“Pointer Stars”
“Big Dipper”
Chart 1 Problem
• Find the coordinates of Capella.
SFA Star Chart 1
How do you use these charts to view
the night sky?
• Chart 1
– Face North
– Find Meridian
– Find the Field of View
SFA Star Chart 1
Today’s Date
Today’s Date
North Horizon
Circumpolar
Stars are stars
that never set.
Charting the Sun’s Path
• Go to Charts 2 and 3
Summer Solstice
Ecliptic
Orion
Autumnal Equinox
Celestial Equator
Vernal Equinox
“Summer Triangle”
Celestial Equator
Autumnal Equinox
Vernal Equinox
Winter Solstice
Ecliptic
Chart 2 Problems (write in questions)
• Find the coordinates of Betelgeuse.
• Where is the Sun on March 15th?
• Where is the Sun on your Birthday?
How do you use these charts?
• Charts 2 & 3
– Face South
– Find Meridian
– Find the Field of View
Field of
View
West Horizon
East Horizon
Celestial Meridian
for Today
SFA Star Chart 4
The Horizon System
•
•
•
•
•
Meridian
Polaris
Zenith
Altitude
Azimuth
Measuring Angles
• Altitude - the angle of a star above the horizon
• The North Star, Polaris, is not the brightest star in the
sky but remains in a fixed position in the sky.
• The angle of Polaris above your horizon is the same
as your latitude in degrees.
We can describe the angular position of an object in the
sky by its altitude (a) above the horizon...
...and by its angular distance from the northmost point
on our horizon, i.e. its azimuth (A) ...
...both measured in degrees.
For
example:
a
A
horizon
north west
north
north east
View from the Equator
View from the North Pole
Precession
• Precession is the slow wobble of the Earth’s
axis due to the influence of the Moon.
• This means that Polaris will not be the North
Star forever....
...just for the rest of our lives.
• This is also why the Zodiac signs are no
longer correct. e.g. Ophiuchus
Precession
•
http://www.bing.com/images/search?q=precession&view=detail&id=249F77B3F23163F2B714DE90963BE9793
2FCF87D&adlt=strict
Precession
Motions of the Sun and Stars
• Daily Motion
– The rising and setting of the stars is caused
by the Earth’s rotation about its axis.
• Annual Motion
– The Earth’s orbit around the Sun causes
different stars and constellations to be visible
at different times during the year.
Constellations
• Constellations are recognizable patterns of
stars in the sky.
• There are 88 constellations. (e.g. Orion)
• The 13 constellations along the ecliptic on
your star chart are called the Zodiac
Constellations.
The
Constellation
Orion
Asterisms
• Asterism are recognizable patterns of stars
that is not one of the 88 constellations.
• For Example: The Big Dipper
Constellations
• Most bright stars have names
-Mixed origin (Greek, Latin, Arabic)
• All stars in the constellations are identified
related to their brightness
-using Greek alphabet symbols
- Usually α = brightest star, then β, then γ, etc.
Magnitude
• A stars apparent magnitude is also identified
Lower number = Brighter star
Higher number = Dim star
We can make a rough estimate of the
angular separation of objects in the night sky
by holding our hand out at arm’s length:
A finger’s width is roughly 1o,
1o
And a fist’s width is roughly 10o
10o