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Astrophotography in the Classroom. For SEEC 2014 at NASA JSS David O’Dell, Anderson HS. Goals of this presentation. Show you how to: bring real astrophotography into your classroom use image processing software use image measurement software All this AND get the kids to enjoy it.

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astrophotography in the classroom

Astrophotography in the Classroom

For SEEC 2014 at NASA JSS

David O’Dell, Anderson HS

goals of this presentation
Goals of this presentation
  • Show you how to:
  • bring real astrophotography into your classroom
  • use image processing software
  • use image measurement software
  • All this AND get the kids to enjoy it
why take your curriculum this direction
Why take your curriculum this direction?
  • Real science
  • Software is free
  • Learning curve is low
  • Student driven activity
  • Personal challenge (to you AND students!)
  • Transfer of skills to other activities
deciding which type of astrophotography will fit in your curriculum
Deciding which type of Astrophotography will fit in your curriculum
  • 2 types… each with their own set of hardware, price tag and challenges:
  • Deep Sky
  • Webcam
deep sky astrophotography
Deep Sky Astrophotography
  • Most difficult, by far
  • Most expensive
  • Most rewarding (some say):
    • More objects out there than our solar system
    • “cooler looking” stuff like galaxies, colorful nebulae
webcam astrophotography
Webcam Astrophotography
  • Super easy
  • Extremely cheap
  • Still very rewarding, just in different ways
  • … it’s what this presentation will cover!
you can do so much without a telescope you just need
You can do so much without a telescopeYou just need:
  • Access to a few (or many) PC windows-based computers
  • Permissions to install two small FREE software packages on those machines
    • AVI stack
    • Image J
  • Sample videos and images (simply search online for .avi files)
but much more with a telescope
…but much more with a telescope
  • All the previous items +
  • A single Windows XP or Win 7 laptop
    • Usually from your school, or your personal one
  • Low Luxor comparable Web cam
    • Usually less than $100
    • Philips SPC 900NC, or the 700NC
  • Sharp Cap web cam software
    • FREE
  • 1.25 “ Web cam telescope eyepiece adapter
    • $15 to $30, search “1.25 web cam adapter” on EBAY
  • … and of course… ANY size telescope
well think about what scientists collect
Well… Think about what scientists collect…
  • Zoologists collect?
  • Animals!
  • Entomologists collect?
  • Bugs!
  • Philatelists collect?
  • Stamps!
  • Numismatics collect?
  • Coins!
  • Astronomers collect?????
  • LIGHT!
astronomy specific issues
Astronomy specific issues
  • Astrophotography environment is special
    • At night mostly
    • Large contrast
      • Night sky objects are bright compared to dark space
    • Moist or cloudy air
    • Windy ground or upper altitude air turbulance
    • Objects difficult to find
    • Object difficult to focus
    • Objects appear to move as Earth rotates
    • Digital cameras generate waste heat, interference
    • Objects need long exposure times…
deep sky ccd chip cameras
Deep Sky CCD chip cameras
  • Specially designed:
    • stay “cool” to reduce hot pixels
    • Keep shutter open for long exposure times
    • Large CCD chip that is extremely sensitive to very low light
    • Some only B&W, some color
    • Fit inside a telescope eyepiece tube
    • Software controlled capture settings
ccd light sensitivity
CCD Light sensitivity
  • CCD will collect photons over a long period of time and produce a bright image from a dim object
  • Long exposures are only possible if the telescope “tracks” the object
  • If scope does not track object, the image is smeared across the CCD
deep sky vs webcam imaging
Deep sky vs. Webcam imaging
  • Solar system objects are considerably closer and appear larger compared to deep sky objects thousands of light years away… We don’t need the extreme sensitivity of a CCD.
  • A planetary “webcam” is the best option for bright and relatively large solar system objects. Uses low power, less sensitive CMOS chip.
  • Instead of long risky exposure times, the webcam takes hundreds of millisecond frames that are processed later using software
settings to pay attention to
Settings to pay attention to:
  • Focus – webcams and CCD cameras are particularly sensitive to focus shift!! Light travels a shorter distance than through an eyepiece, so focus is as if you had a 6 mm lens; very sensitive to any movement.
  • Might need a focal reducer: Antares 1.25" 0.5x Focal Reducer
  • Gain – # photons that fall on that pixel are multiplied by a certain amount; image might be brighter, but less accurate
  • Exposure – amount of time shutter is open, measured in seconds or the number of frames you record
taking a set of darks
Taking a set of “Darks”
  • Cameras all leak voltage out of the image chip
  • This leakage occurs in a predictable pattern
  • A long exposure image with the lens cap ON is taken and the hot pixels are mapped and removed by software
the basic astrophotography process
The basic astrophotography process:
  • Setup scopes, camerasand computer; let cameras settle for 5 minutes to get used to the ambient temperature
  • Take a set of darks
  • Find object and focus using eyes
  • Place camera in eyepiece, reposition and focus using camera / computer
  • Choose settings and record video (using Sharp Cap)
  • Do not walk nearby or touch scope while imaging
  • Save file for processing later
onto the processing process
Onto the processing… process
  • Frame selection
  • Alignment
  • Stacking
  • Post processing
  • Scientific Measurement & Comparison

Using AVI stack

Using Image J


The following process is to “get the job done”. For specialized tweaks, please read the AVI Stack manual

loading a file into avi stack
Loading a file into AVI Stack
  • Open .avi movie file from your webcam into AVI stack
  • Highlight file
  • Frames will be counted
at any point you can make changes
At any point you can make changes
  • Each segment of the process is compartmentalized
  • Simply click on a green folder in the Parameters and Settings window
  • Make the changes and move on
frame selection my 1 tip
Frame Selection – my #1 tip
  • More frames doesn’t mean a better image.
  • Remember, pixels are the carriers of visual information. Too much might be over kill.
  • You will NEVER need all the frames of video
  • For most webcam images of the moon and planets, you’ll need no more than 500 frames; and only end up selecting around 200 of those to process.
frame selection
Frame Selection
  • Using the video slider, scroll through the frames and find ones that have problems such as dust, blur, birds, shakes and wild changes of position
  • On frame selection panel, highlight, then ‘X’ them out in bulk using ‘shift’ key or one by one
  • Click OK
frame alignment parameters
Frame Alignment Parameters
  • Using frame selector slider, scroll to the clearest frame
  • Select “planet”, or “surface” for close-up lunar surfaces
  • Adjust “area radius”
  • Left click to place 1st alignment box, right click for 2nd box.
  • Boxes should be on top of unique features
  • Click OK
alignment deviation the one graph you get to play with
Alignment Deviation – the one graph you get to play with
  • Too much deviation is bad.
  • You want to reduce the number of frames used that have large alignment deviation from the previous frame
reducing deviated frames
Reducing Deviated frames
  • Click and drag the top axes of the top graph and pull the red line down, this will be the new cutoff.
  • Frames that deviate too far (over 4 pixels in this example) will not be stacked
  • Click OK
framed aligned movie
Framed Aligned Movie
  • This is where the software first shows its true power
  • Using the movie slider, scroll through the frames
  • You’ll see that the image doesn’t move very much at all now
  • Click OK
roi region of interest selection
ROI (Region of Interest) Selection
  • Simply drag a selection box around the part of the image you want to stack
  • Click OK
initial stack reference point settings for most images
Initial Stack Reference Point settings for most images
  • Used to help stacking and quality management process
  • Minimum distance below 18 is not recommended
  • Structure threshold around 70 recommended
  • Lower cut off 0
  • Upper cut off 1
  • Tweaking these is most often used only with extremely noisyimages
quality analysis
Quality Analysis
  • Some frames contain better, sharper information in certain parts MORE than other frames.
  • AVI stack can break up each frame into areas and make a quality judgment for use in the stacking process
quality analysis settings for most images
Quality Analysis settings for most images
  • Standard quality method selected
  • Noise reduction is suggested to be 1 unless you have extremely noisy
  • Quality area set to above 50, default is 84.
  • Click OK
frame quality diagram
Frame quality diagram
  • Shows a quality vs. frame curve.
  • The highest quality frames will be first in the sorted list
quality sorted movie
Quality sorted movie
  • Simply scroll through the frames of the movie and you will see that sharper, high quality frames are first
  • Low quality frames are last
  • Click OK
final reference point alignment
Final reference point alignment
  • Area radius around 25
  • Search radius is best left automatic since this is calculated
  • Quality cut off IS EXTREMELY IMPORTANT, choose to use first 30% of frames, or, use a specific number of frames by checking frame cut off
frame stacking
Frame Stacking
  • Screen will be black, this is normal
  • Click OK and watch the quality sections appear and stack piece by piece
  • Some errors and dust specks might disappear!
why stack the picture looks pretty good
Why Stack? The picture looks pretty good!
  • You might have one single color image, however, it may not be enough pixels to make a truly magazine quality image
  • You need LOTS and LOTS of combined images
  • You need to STACK your images
image stacking no pixel left behind
Image Stacking – No Pixel Left Behind!
  • Image stacking is a process where many frames of an image are placed on top of one another to increase the amount of pixel coverage
saving stacked image
Saving stacked image
  • Choose the filename and directory you want to save to
  • Click Save
  • You’re not done…
post processing
  • Click the “post processing” green folder
  • Wavelets, Levels, Histogram and Clipping
  • Only Wavelets and Levels are needed
wavelets and levels
Wavelets and Levels
  • Adjust the wavelet sliders to sharpen your image or bring out certain surface details
  • Top slider of a layer is the amount, bottom slider is amplitude
  • Levels are easily adjusted to help control color contrast
saving post processed image
Saving Post Processed image
  • You will need to save this image as a new image
  • AVI stack will automatically append the suffix _pp to the end of your filename
basic measurement with image j
Basic measurement with Image J
  • Image J only recognizes pixel dimensions, it has no idea the scale of any image
  • First priority is to set some sort of scale of pixels to km or miles
  • Easily done as long as the object has a known diameter
  • Diameters of all planets, moons, volcanoes and major craters are on Google
how to set scale using a known distance
How to set scale using a known distance
  • Open image into Image J
  • Using the line segment tool, draw a diameter line across the object
  • Type in the ‘known distance’
  • Set units
  • Click OK
choosing measurements to display
Choosing measurements to display
  • Check fields you want to display and measure
  • Click OK
making measurements
Making measurements
  • Using the line segment, freehand, or ellipse tool find a feature and draw over or around it
  • A new results window will appear
  • Repeat process and new measurements will appear in window
comparison of scale
Comparison of Scale
  • Astronomical measurements are usually on extreme scales
  • It helps students comprehend scale by comparing the measured object’s size to something familiar on Earth, such as:
  • Distance to a nearby city
  • How many New England states could fit into…
  • Or simply, number of Earth diameters
any questions contact me
Any Questions, Contact me!
  • David O’Dell
  • Anderson High School, Austin TX