constellations a natural human tendency is to see patterns and relationships between objects even...
TRANSCRIPT
ConstellationsA natural human tendency is to see patterns and relationships
between objects even when no true connection exists.
Long ago, people connected the brightest stars into configurations called constellations, which ancient astronomers named after mythological beings, heroes, and animals—whatever was important to them.
Does that cloud look like a “bunny” to you.
OR
What do you see in that ink blot?
Orion• Some locations are better
• Stars are widely varied in color
Orion
Ursa Major
Ursa Major
Ursa Minor
Ursa Minor
Scorpius
Scorpius
Cygnus
Cygnus
Sagittarius
Sagittarius
Cross CulturesAstronomers of ancient China saw mythical figures different
from those seen by the ancient Greeks, the Babylonians, and the people of other cultures, even though they were all looking at the same stars in the night sky.
Interestingly, though, different cultures often made the same basic groupings of stars, despite widely varying interpretations of what they saw.
For example, the group of seven stars usually known in North America as "the Dipper" is known as "the Wagon" or "the Plough" in Western Europe. The ancient Greeks regarded these same stars as the haunches and tail of "the Great Bear," while the Egyptians saw them as the leg of an ox.
NavigationReasons to Group stars and create constellations:
• Entertainment
• Honor – Hero Hall of Fame– gods or leaders
• Keep track of where things are and the time– Calendars, Events
• Navigation
Patterns are Deceiving
Constellations are NOT
physically associated
with each other, they just happen
to be along your line of sight.
Our Moving Observatory
Star trails
Looking SouthEast
Looking North
What’s Your SignThe Sun’s Position Determines your sign.
The Zodiac
Summer ConstellationsLooking South
Lyra and CygnusDirectly
Overhead
After Sunset
in the summer
and early
fall.
Winter ConstellationsLooking South
Star Atlas ArtistryCan You Find:
Orion
Taurus
Canis Major
Cancer
Gemini
HipparchusMost atlases of today have their origins with those
that were derived from Hipparchus and used his
“magnitude” system.
1st Rank Stars (The brightest stars in the sky)
6th Rank Stars (Barely visible with the unaided eye)
Later, the magnitudes were rigorously defined so
that a 5 magnitude difference = 100 x the intensity.
MagnitudesMagnitudes
are more
precise
and changes
in intensity
are matched
with apparent
magnitudes.
Vega = 0.0
Magnitude ScaleNote:
M = 5 - 0 = 5
I = 100 1 = 100
or
M = 8 - 3 = 5
I = 1600 160 = 100
Brightness ScaleI1/I2 = 2.512(m2-m1)
I = intensity mv = apparent magnitude
• Horizon based coordinate system– Horizon dependent (different for each observer)
Altitude - Azimuth
S
W
N
E
• Horizon based coordinate system– Horizon dependent (different for each observer)
• Azimuth Angle (degrees)– measured CW from N to E– N = 0o, E = 90o, S = 180o, W = 270o
Altitude - Azimuth
S
W
N
E
N
0
180
90 E
S
270W
• Horizon based coordinate system– Horizon dependent (different for each observer)
• Azimuth Angle (degrees)– measured CW from N to E– N = 0o, E = 90o, S = 180o, W = 270o
• Altitude Angle(degrees)– horizon to star– Horizon = 0o
– Zenith = 90o
Altitude - Azimuth
S
W
N
E
N
0
180
90 E
S
270W
“Bowl” DiagramOrienting yourself to a local horizon.
N S
W
NCP
Zenith
Celestial Equator
Celestial Orientation
Right Ascension - Declination• Geocentric Coordinates
– Observer Independent
Towardthe VernalEquinoxe (Position of the Sun on March 21-22
Celestial Equator(Earth’s Equator)
North Celestial Pole (NCP)
Right Ascension - Declination
Towardthe VernalEquinoxe = 0 hours
Celestial Equator(Earth’s Equator)
• Right Ascension (hours)– Measured from the Vernal Equinoxe along the C.E.– Vernal Eq. = 0 hours
RA
Right Ascension - Declination
Towardthe VernalEquinoxe = 0 hours
Celestial Equator(Earth’s Equator)
• Declination (degrees)– Measured from the Celestial Equator to the Pole– CE = 0o
– NCP = 90o
NCP
DEC
Sky Atlas
Right Ascension
Dec
lina
tion
Magnitude
Sky Atlas
Constellation
Lyra,
Bright Star
Vega