Astrophotography in the Classroom

  • View
    40

  • Download
    0

Embed Size (px)

DESCRIPTION

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. - PowerPoint PPT Presentation

Text of Astrophotography in the Classroom

Image Processing

Astrophotography in the ClassroomFor SEEC 2014 at NASA JSSDavid ODell, Anderson HS

Goals of this presentationShow you how to:bring real astrophotography into your classroomuse image processing softwareuse image measurement softwareAll this AND get the kids to enjoy itWhy take your curriculum this direction?Real scienceSoftware is freeLearning curve is lowStudent driven activityPersonal challenge (to you AND students!)Transfer of skills to other activities

Deciding which type of Astrophotography will fit in your curriculum2 types each with their own set of hardware, price tag and challenges:Deep SkyWebcamDeep Sky AstrophotographyMost difficult, by farMost expensiveMost rewarding (some say):More objects out there than our solar systemcooler looking stuff like galaxies, colorful nebulae

Webcam AstrophotographySuper easyExtremely cheapStill very rewarding, just in different ways its what this presentation will cover!

You can do so much without a telescopeYou just need:Access to a few (or many) PC windows-based computersPermissions to install two small FREE software packages on those machinesAVI stackhttp://www.avistack.de/download.htmlImage Jhttp://rsbweb.nih.gov/ij/Sample videos and images (simply search online for .avi files)http://www.skyimaging.com/astronomy-videos.php

but much more with a telescopeAll the previous items +A single Windows XP or Win 7 laptopUsually from your school, or your personal oneLow Lux or comparable Web cam Usually less than $100Philips SPC 900NC, or the 700NChttp://nightskyinfocus.com/equipment/philips-spc900nc00-webcam-for-astrophotography/Sharp Cap web cam softwareFREEhttp://www.sharpcap.co.uk/sharpcap/downloads1.25 Web cam telescope eyepiece adapter$15 to $30, search 1.25 web cam adapter on EBAY and of course ANY size telescope

Why do we need the stuff we need to do this?!?Well Think about what scientists collectZoologists collect?Animals!Entomologists collect?Bugs!Philatelists collect?Stamps!Numismatics collect?Coins!Astronomers collect?????LIGHT!

Astronomy specific issuesAstrophotography environment is specialAt night mostlyLarge contrast Night sky objects are bright compared to dark spaceMoist or cloudy airWindy ground or upper altitude air turbulanceObjects difficult to findObject difficult to focusObjects appear to move as Earth rotatesDigital cameras generate waste heat, interferenceObjects need long exposure timesDeep Sky CCD chip camerasSpecially designed:stay cool to reduce hot pixelsKeep shutter open for long exposure timesLarge CCD chip that is extremely sensitive to very low lightSome only B&W, some colorFit inside a telescope eyepiece tubeSoftware controlled capture settings

CCD Light sensitivityCCD will collect photons over a long period of time and produce a bright image from a dim objectLong exposures are only possible if the telescope tracks the objectIf scope does not track object, the image is smeared across the CCD

Deep sky vs. Webcam imagingSolar system objects are considerably closer and appear larger compared to deep sky objects thousands of light years away We dont 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: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 ReducerGain # photons that fall on that pixel are multiplied by a certain amount; image might be brighter, but less accurateExposure amount of time shutter is open, measured in seconds or the number of frames you record

Taking a set of DarksCameras all leak voltage out of the image chipThis leakage occurs in a predictable patternA long exposure image with the lens cap ON is taken and the hot pixels are mapped and removed by software

The basic astrophotography process:Setup scopes, cameras and computer; let cameras settle for 5 minutes to get used to the ambient temperatureTake a set of darksFind object and focus using eyesPlace camera in eyepiece, reposition and focus using camera / computerChoose settings and record video (using Sharp Cap)Do not walk nearby or touch scope while imagingSave file for processing later

Onto the processing processFrame selectionAlignmentStackingPost processingScientific Measurement & ComparisonUsing AVI stackUsing Image JThe following process is to get the job done. For specialized tweaks, please read the AVI Stack manualhttp://www.avistack.de/downloads/AviStack2_eng.pdf

Loading a file into AVI StackOpen .avi movie file from your webcam into AVI stackHighlight fileClick PROCESS FILEFrames will be counted

At any point you can make changesEach segment of the process is compartmentalizedSimply click on a green folder in the Parameters and Settings windowMake the changes and move on

Frame Selection my #1 tipMore frames doesnt 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 videoFor most webcam images of the moon and planets, youll need no more than 500 frames; and only end up selecting around 200 of those to process.Frame SelectionUsing the video slider, scroll through the frames and find ones that have problems such as dust, blur, birds, shakes and wild changes of positionOn frame selection panel, highlight, then X them out in bulk using shift key or one by oneClick OK

Frame Alignment ParametersUsing frame selector slider, scroll to the clearest frameSelect planet, or surface for close-up lunar surfacesAdjust area radiusLeft click to place 1st alignment box, right click for 2nd box.Boxes should be on top of unique featuresClick OK

Alignment Deviation the one graph you get to play withToo much deviation is bad.You want to reduce the number of frames used that have large alignment deviation from the previous frame

Reducing Deviated framesClick 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 stackedClick OK

Framed Aligned MovieThis is where the software first shows its true powerUsing the movie slider, scroll through the framesYoull see that the image doesnt move very much at all nowClick OK

ROI (Region of Interest) SelectionSimply drag a selection box around the part of the image you want to stackClick OK

Initial Stack Reference Point settings for most imagesUsed to help stacking and quality management processMinimum distance below 18 is not recommendedStructure threshold around 70 recommendedLower cut off 0Upper cut off 1Tweaking these is most often used only with extremely noisy images

Quality AnalysisSome 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 imagesStandard quality method selectedNoise reduction is suggested to be 1 unless you have extremely noisyQuality area set to above 50, default is 84. Click OK

Frame quality diagramShows a quality vs. frame curve. The highest quality frames will be first in the sorted list

Quality sorted movieSimply scroll through the frames of the movie and you will see that sharper, high quality frames are firstLow quality frames are lastClick OKFinal reference point alignmentArea radius around 25Search radius is best left automatic since this is calculatedQuality 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 StackingScreen will be black, this is normalClick OK and watch the quality sections appear and stack piece by pieceSome errors and dust specks might disappear!

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 imageYou need LOTS and LOTS of combined imagesYou need to STACK your imagesImage 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

StackingExamplesSaving stacked imageChoose the filename and directory you want to save toClick SaveYoure not done

Post-ProcessingClick the post processing green folderWavelets, Levels, Histogram and ClippingOnly Wavelets and Levels are needed

Wavelets and LevelsAdjust the wavelet sliders to sharpen your image or bring out certain surface detailsTop slider of a layer is the amount, bottom slider is amplitudeLevels are easily adjusted to help control color contrast

Saving Post Processed imageYou will need to save this image as a new imageAVI stack will automatically append the suffix _pp to the end of your filename

Great results either way, ready for scientific measurement!!Stacked ONLY

After post-processingBasic measurement with Image JImage J only recognizes pixel dimensions, it has no idea the scale of any imageFirst priority is to set some sort of scale of pixels to km or milesEasily done as long as the object has a known diameterDiameters of all planets, moons, volcanoes and major craters are on Google

How to set scale using a known distanceOpen image into Image JUsing the line segment tool, draw a diameter line across the objectClick ANALYZE > SET SCALEType in the known distanceSet unitsClick OK

Choos