Astrophotography in the Classroom

1. Astrophotography in the Classroom For SEEC 2014 at NASA JSS David O’Dell, Anderson HS

2. 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

3. 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

4. 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

5. 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

6. Webcam Astrophotography • Super easy • Extremely cheap • Still very rewarding, just in different ways • … it’s what this presentation will cover!

7. 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 • http://www.avistack.de/download.html • Image J • http://rsbweb.nih.gov/ij/ • Sample videos and images (simply search online for .avi files) • http://www.skyimaging.com/astronomy-videos.php

8. …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 • http://nightskyinfocus.com/equipment/philips-spc900nc00-webcam-for-astrophotography/ • Sharp Cap web cam software • FREE • http://www.sharpcap.co.uk/sharpcap/downloads • 1.25 “ Web cam telescope eyepiece adapter • $15 to $30, search “1.25 web cam adapter” on EBAY • … and of course… ANY size telescope

9. Why do we need the stuff we need to do this?!?

10. Well… Think about what scientists collect… • Zoologists collect? • Animals! • Entomologists collect? • Bugs! • Philatelists collect? • Stamps! • Numismatics collect? • Coins! • Astronomers collect????? • LIGHT!

11. 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…

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. Onto the processing… process • Frame selection • Alignment • Stacking • Post processing • Scientific Measurement & Comparison Using AVI stack Using Image J

19. The following process is to “get the job done”. For specialized tweaks, please read the AVI Stack manualhttp://www.avistack.de/downloads/AviStack2_eng.pdf

20. Loading a file into AVI Stack • Open .avi movie file from your webcam into AVI stack • Highlight file • Click PROCESS FILE • Frames will be counted

21. 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

22. 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.

23. 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

24. 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

25. 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

26. 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

27. 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

28. ROI (Region of Interest) Selection • Simply drag a selection box around the part of the image you want to stack • Click OK

29. 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

30. 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

31. 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

32. Frame quality diagram • Shows a quality vs. frame curve. • The highest quality frames will be first in the sorted list

33. 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

34. 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

35. 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!

36. 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

37. 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

38. StackingExamples

39. Saving stacked image • Choose the filename and directory you want to save to • Click Save • You’re not done…

40. Post-Processing • Click the “post processing” green folder • Wavelets, Levels, Histogram and Clipping • Only Wavelets and Levels are needed

41. 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

42. 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

43. Great results either way, ready for scientific measurement!! • Stacked ONLY • After post-processing

44. 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

45. 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 • Click ANALYZE > SET SCALE • Type in the ‘known distance’ • Set units • Click OK

46. Choosing measurements to display • Click ANALYZE > SET MEASUREMENTS • Check fields you want to display and measure • Click OK

47. Making measurements • Using the line segment, freehand, or ellipse tool find a feature and draw over or around it • Click ANALYZE > MEASURE • A new results window will appear • Repeat process and new measurements will appear in window

48. 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

49. Any Questions, Contact me! • David O’Dell • Anderson High School, Austin TX • david.odell@austinisd.org