Transcript Star Gazing

Objectives
•
•
•
•
•
•
•
•
•
•
•
Identify and use the correct color light to maintain dark adaptation when
stargazing.
Observe and record the position of the sun at sunset.
*Describe positions of stars, Moon, Sun on the sky using direction and
altitude.
*Measure altitudes using the fist method.
Define and use horizon and zenith.
Correctly hold and orient a star chart and use it to find stars and
constellations.
Practice star hopping to locate stars and constellations.
*Explain why the date and time are included on star charts
State the magnitude scale for stars. Given a star’s magnitude, identify if it is
bright or faint.
Identify the first four Greek letters. For what do astronomers use them?
Define rotation and revolution as used by astronomers. Use them correctly
when describing the motion of Earth, other planets, Sun and Moon.
Star Gazing
• Star Gazing techniques and tips: how to
get the most out of looking up at the stars
(slideshow on class website – mctcteach.org)
• Show 2 flashcards to me.
• Email me if you haven’t yet stating, “I found the
class website and slideshows.” Details in the
notes from last Tuesday.
• If you haven’t given me a code to use for your
grades on the class website, see Raquel.
Sky Software
•
•
•
•
•
Starry Night College ($30)
SkyX
Stellarium (free)
Celestia (free)
Google Earth and Google Sky
https://www.google.com/sky/ (free)
Sky Phone Apps (all free)
•
•
•
•
•
•
•
Google Sky
Star Chart or Sky Map
Phases of the Moon
Sunrise Sunset
ISS Detector (International Space Station)
NASA
Lots of other star apps out there
Positions in the sky - Direction
• How can you find N, S, E, or W?
Positions in the sky - Direction
• How can you find N, S, E, or W?
– Compass
– Phone/GPS/Car
– Map
– North Star = Polaris
Positions in the sky - Altitude
• Horizon – intersection of Earth and sky
– About eye level
• Zenith – point in sky directly overhead
– 90 degrees
– Halfway: 45 degrees
• Fist Method: Extended fist is ~10 degrees
Exercise (Height of building from ground)
Star Charts
• Print current month of the Sky Map if you
missed lecture:
• http://skymaps.com/downloads.html
• Finding N, S, E, W
• Orienting the star chart
– If you face N, hold N down on the chart,
closest to you.
From Star Chart to Sky
• Note where constellation is on map
(direction and altitude)
• Use fist method to find it in sky
• Examples
– Polaris
– Venus
Star Hopping
• Ursa Major to Ursa Minor (Polaris), use pointing
stars
• Ursa Major: arc to Arturus (in Bootes)
• Cassiopeia: left V eats Polaris
• Cassiopeia: right V points to Andromeda (only
galaxy visible to the naked eye); then
Andromeda curves to Great Square of Pegasus
• Summer/Fall: Deneb (NE) to Altair (southern tip
of Summer Triangle) points to bottom left of The
Teapot handle
• Winter/Spring: Orion’s belt, left to Sirius, right to
Aldebaran (Taurus) and Pleiades
Greek Letters on star charts
•
•
•
•
•
Brightest stars in that constellation
Alpha ( α )
Beta ( β )
Gamma (γ )
Delta ( δ )
• Example: Deneb in Cygnus is Alpha Cygni
Why is the TIME on the
star chart?
Why is the TIME on the
star chart?
• Earth’s Rotation…
– Displays different constellations throughout
the night
• In the northern hemisphere, the stars
appear to rotate around Polaris, the North
Celestial Pole.
Polaris, the North Star, with all of the stars moving
around it. The star trails are from the Earth’s rotation.
http://apod.nasa.gov/apod/ap091128.html
Why is the DATE on the
star chart?
Why is the DATE on the
star chart?
• Earth’s Revolution...
– Displays different constellations throughout
the year
Planisphere
- North on front
- South on back
For more
instructions about
how to use a
planisphere:
http://astronomy.s
ierracollege.edu/C
ourses/Astronomy
02/Planisphere.ht
m
• 12 Constellations of the Zodiac seen throughout the year
because of Earth’s revolution.
• The zodiacal constellations are located along the Sun’s path on
Earth (Ecliptic).
• The Ecliptic is also the plane of Earth’s path around the Sun.
http://lifeng.lamost.org/courses/astrotoday/CHAISSON/AT301/HTML/AT30103.HTM
Apparent Visual Magnitude
• Hipparchus
– 1 (first magnitude)
bright to eye
– 2 (second magnitude) fainter
– …6 (sixth magnitude) faintest to eye
– 1st magnitude is 100 times brighter than the
6th magnitude
– Originally based on Polaris (app. mag. = 2)
– Now extended to negative numbers
– Example: Sirius, brightest star in the sky has
magnitude -1.5
Dark Adaptation
In dark, eye pupil enlarges to let in more light.
In sun, pupil shrinks to keep out light.
Exercise with dim lights
Dark Adaptation
• When star gazing, eye pupil needs to open
up (~15 minutes)
• Eyes have cones and rods
(photoreceptors)
– Cones see color & adapt to darkness quickly
– Rods take 10-30 minutes to adapt to darkness
• Pupil shuts down quickly in response to
white light but not to red light.
• Therefore use red flashlights.
Dark Adaptation
1.
2.
3.
4.
Show red covered flashlights
Turn lights off and use curtains
Show colors displayed around the room
Color differentiation disappears after 10
minutes (color is from cones)
5. About 15 minutes in, rods take over; no
color and now see light trails (sparklers);
laser demo
Dark Adaptation Blind Spot
• Little dipper & Polaris example
http://www.optics4kids.org/getattachment/13cb7b00-117a-4e69-9d5d-35ad7d949199/OpticalIllusions.aspx
Eye Blind Spot
• Cross-dot demo of blind spot (draw on paper)
http://www.optics4kids.org/getattachment/13cb7b00-117a-4e69-9d5d35ad7d949199/Optical-Illusions.aspx
Observations
• Star Gazing Observation (25 points)
– Main Goal: See constellations in night sky
• Telescope Observation (25 points)
– Main Goal: Look at night sky through a telescope
• Moon Craters Observation (10 points)
•
•
•
•
– Main Goal: see Moon’s craters under magnification
Until May 4th to complete
Many Options for each of these 3 observations
Class website has more details. View Special Events.
Turn in verification sheet (unless you check-in with me at the
event).
Homework
• Continue flashcards of objectives
• Email me if you haven’t yet stating, “I
found the class website slideshows.”
Details in the notes from last Tuesday.
• If you haven’t given me a code to use for
your grades on the class website, see me.
• Work on Earth-Sun Scale Model (10
Observation Points)
• If you haven’t shown me your flashcards
yet, do so now.