Transcript Youth AstroNet Program - The Challenger Learning Center

Youth AstroNet Program
Introduction
This presentation based on information and materials from
The Harvard-Smithsonian Center for Astrophysics Science Education Portal
http://waps.cfa.harvard.edu/eduportal/
Questions about this presentation? Contact Carolyn Donelan @ [email protected]
What is light?
Image credit: http://missionscience.nasa.gov/ems/01_intro.html
Telescopes
• Telescopes gather light from a distant object and focus that light into
an image.
• A simple telescope:
Image from: http://www.worldknowledgebase.com/wp-content/uploads/2016/07/eye_xsection_01.jpg
Refracting Telescopes
• Refracting telescopes were invented
by 1608.
• Refracting telescopes use lenses to
gather and focus light.
• The size of the refracting telescope
is limited by the size of the lens you
can make.
Image from: http://www.bbc.co.uk/staticarchive/2648417c1b83c1609086caa1279537d9e33ebd93.jpg
Refracting Telescopes
• The largest refracting telescope is
the Yerkes Telescope. It is located
in Wisconsin and is run by the
University of Chicago.
• The objective lens is 40 inches in
diameter; the steel tube is 69 feet
long.
Image from: http://storage.lib.uchicago.edu/ucpa/series6/derivatives_series6/apf6-00030r.jpg
Refraction
• When light waves change
direction as they pass from one
medium to another.
Image credit: http://images.tutorvista.com/cms/images/83/index-of-refraction.jpg
Refraction
• Different wavelengths of
light slow (or speed up) at
different rates in the same
medium.
Image credit: https://upload.wikimedia.org/wikipedia/commons/thumb/f/f5/Light_dispersion_conceptual_waves.gif/495px-Light_dispersion_conceptual_waves.gif
Refraction with Lenses
Image credit: http://sciencefacts.net/wp-content/uploads/2015/12/Converging-Vs-Diverging-Lens.jpg
Reflecting Telescopes
• Reflecting telescopes were
invented in 1668 or 1669 (by Sir
Isaac Newton).
• Reflecting telescopes use a mirror
to gather and focus light and
another mirror to direct the light
to an eyepiece or camera.
Image credit: http://www.bbc.co.uk/staticarchive/4d2837a01269607d33a14791d3e142cec0621cc7.jpg
Reflecting Telescopes
• The largest single mirrors
telescope ever built is the
Large Binocular Telescope,
which has mirrors which
are 8.4 meters (27.6 feet)
in diameter.
• The Large Binocular
Telescope is located in
Arizona.
Image credit: http://ast.noao.edu/img/lbt2.jpg
Image credit: http://jwst.nasa.gov/widgets/spacecraftExplorer/code/images/scView_f2.png
Reflecting Telescopes
• The Keck telescopes in Mauna
Kea, Hawaii, have a 10 meter
mirror, which is composed of 36
smaller hexagonal mirrors.
Image credit: http://www.astro.caltech.edu/research/keck/mirror.jpg
• The James Webb
Telescope will have a 6.5
meter mirror (composed
of segments). It is
scheduled to launch
October 2018.
Image credit: http://www.physicsclassroom.com/mmedia/optics/rdcmc.cfm
Reflection
• When light hits an object and
bounces off
Image credit: http://www.physics.wisc.edu/ingersollmuseum/exhibits/optics&color/3mirrors
Other Types of Telescopes
• Reflecting and refracting telescopes are optical telescopes, because
they collect visible light.
Image credit: http://www2.lbl.gov/images/MicroWorlds/EMSpec.gif
Other Types of
Telescopes
• NASA has telescopes that
cover the range of the
electromagnetic spectrum.
• Want to learn more about
the electromagnetic
spectrum? Go here:
http://missionscience.nasa.
gov/ems/
Image credit: http://image.slidesharecdn.com/tourofemsbookletweb151120114532-lva1-app6892/95/tour-ofems-bookletweb-17638.jpg?cb=1448020150
MicroObservatory Telescopes
• These are the telescopes
you will be using.
• These are OPTICAL
telescopes.
• You will be processing
images taken with these
telescopes.
Image credit: http://waps.cfa.harvard.edu/eduportal/course/view.php?id=4
CCD Camera (“Charge Coupled Device”)
• CCDs have sensors that convert
light into electrical charges.
• The more intense the light, the
stronger the electrical charge.
• The CCD then “reads” a value of
the electrical charge.
Image credit: By Andrzej w k 2 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=35704780
Image credit: http://www.rocketroberts.com/astro/images/ccd_01.png
Pixel
• Each sensor on the CCD is called a pixel.
• This image
is a 1,000X
close up of
a CCD.
Image credit: http://www.scientificcomputing.com/news/2012/01/close-ccd-sensor, from Nikon Small World
Short Exposure vs Long Exposure
• Exposure is how long light is allowed to strike the CCD. The more light
that the CCD collects, the more detail the final image will have.
Image credit: https://livebookswordpress.s3.amazonaws.com/uploads/sites/415/2015/07/pair-for-blog.jpg
Over Exposure
• Some objects are very bright. If
you have a long exposure, the
CCD may collect too much light
and you cannot see contrast.
Image credit: http://4.bp.blogspot.com/_kmH9AIva8dU/SZBK05laICI/AAAAAAAAHBU/uiGRPEU2Id8/s320/IMG_7911p-over.jpg
And the Earth is moving…
• The MicroObservatory
Telescopes “track” objects,
so we shouldn’t get blurred
images.
Image source: https://www.google.com/search?q=short+exposure+vs+long+exposure+astronomy&safe=strict&espv=2&biw=1066&bih=461&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi38aS07LPAhUCGz4KHZjeCLMQ_AUIBigB#imgrc=vbG3yi1VxBPiPM%3A
How to Process an Image
• Go to
microobservatory.org
Scroll down…Click on YouthAstroNet Portal
Click on YouthAstroNet Activity Portal
Login?
You should be here:
Scroll down… click on
MicroObservatory Robotic Tools
Click on Use the images in JS9
Hover on Archived Images
• On the menu that appears, click on AndromedaGal (first in the list)
Your image should
look like this…
Important things to notice:
• Scale
• Pixel Value
• Low Brightness Limits
• Shift/Bias
• High Brightness Limits
• Shift/Contrast
Scale and Pixel Value
• Hover over Scale.
• Click on log.
• Then, move your cursor
around the image and try to
find the spot with the
LOWEST Pixel Value.
• What is the LOWEST Pixel
Value you found?
Low Brightness Limits
• Change the Low Brightness
Limits to the lowest pixel
value you found.
(After you type in the value,
press enter on your
keyboard.)
• 280? (top right)
Shift/Bias
• Use the +/- buttons to shift
the color scale so that the
parts of the sky you think
should be dark are dark (but
no so dark that your faint
stars disappear).
Shift/Bias
• There is no right or wrong
answer.
• In the image on the right, I
used a shift/bias of 0.70.
High Brightness Limits
• Try to find the HIGHEST Pixel
Value you can.
• Enter the HIGHEST Pixel Value
you find as the High
Brightness Limit.
• 1163? (little right, little down
of bright spot)
Shift/Contrast
• Use the +/- buttons on
Shift/Contrast to get the dark
parts dark again.
• There is no right or wrong answer.
• In the image on the right, I used a
shift/contrast of 2.20.
Color!
• The MicroObservatory
telescopes only “see” white,
black, and shades of gray.
• Sometimes it is easier to pick
out details when we add color.
• Hover over Color and click on
Frost.
Shift/Bias?
Stretch/Contrast?
• Adjust your Shift/Bias and
Stretch/Contrast settings to
create an image you like.
• There are no right or wrong
answers.
• To save your image in a format
you can use (or print), hover
over Image and click on Save as
PNG.