Viz Tutorial: Exercise 2

This exercise is intended to take about 20 minutes. Please ask in the Whova chat if you run into any problems or need any clarifications. For “big-picture” questions, there will time for a debrief/Q&A after the exercise.

Setup

  1. If you’re still stuck on the setup steps, keep plugging away!
  2. Open a terminal and activate your software environment.
  3. Change to the ~/wwtviz/pywwt-notebooks directory.
  4. Make sure that you’ve checked out the adass32 branch of the Git repository.
  5. If you didn’t do it before, run the command jupyter lab build. It should take a little while to complete.

Basic app launching

  1. Run the command jupyter lab. This should start up JupyterLab and open a browser window rooted in the demo notebooks directory.
  2. Is the main view the JupyterLab “Launcher” panel? If not, use the View → Activate Command Palette menu item, then type New Launcher in the popup, then hit Enter.
  3. The launcher should have a prominent button labeled “AAS WorldWide Telescope”. If not, ask for help in the chat. (Did you activate the tutorial’s software environment?)
  4. Hit the button! The WWT app should load in a new panel.
  5. Play around a little bit. In the “hamburger menu” at the top right of the WWT interface, click Choose Background to bring up the background chooser, and then try different options. You can type in the pop-up to filter the list.

FITS visualization

  1. In the “hamburger menu”, choose the Load WTML collection item, and paste in the following URL: http://data1.wwtassets.org/packages/2021/09_phat_fits/index.wtml.
  2. Now choose the Add imagery as layer item and click on the pop-up entry box. There should be two options. Click on PHAT-f475w to load this image, which is derived from about 20 GiB of FITS data.
  3. Change the background imagery to PanSTARRS1 3pi.
  4. In the “Imagery” panel at the top-left of the UI, click on the line that reads PHAT-f475w. This should expand a panel with controls for adjusting the FITS visualization.
  5. Change the stretch to Logarithmic.
  6. Click on the “target” icon next to the row labeled High cutoff. Now, as you move your mouse around, the upper data cutoff point will change. Moving your mouse towards the left side of the WWT window will reduce its value; moving your mouse towards the right side will increase it. Moving your mouse towards the top edge of the window will make a bigger change; moving your mouse towards the bottom edge will make a smaller change. In this case, moving your mouse towards the top-left of the WWT window will have the biggest effect. Click your mouse button to “commit” the adjustment and exit the adjustment mode.
  7. Do the same with the Low cutoff row. Instead of clicking the mouse button, hit the spacebar. This will “commit” the adjustment but not exit the interactive mode. To adjust one of the cutoffs by a large amount, you would move your mouse to the top-left or top-right corner of the WWT window and hit the spacebar repeatedly.
  8. Move your mouse back over the line labeled PHAT-f475w. Click on the “eye” icon to hide the image. Click it repeatedly to blink the image against the background. Do the stars line up?
  9. Play around with some of the other controls. The “map item” icon next to the “eye” icon returns the view to the image if you pan away from it.
  10. In the Add imagery as layer menu, add the other PHAT image, PHAT-f814w. Tune its appearance and give it a colormap that’s different than the F475W image. Use the opacity controls to try visualize the astrophysical colors of these images.

Kernel controls

  1. Open up the “NASA Exoplanet Archive” demo notebook by double-clicking on its row in the file explorer panel on the left edge of the JupyterLab interface.
  2. Set up a side-by-side view of the WWT app and the notebook by clicking on the notebook’s tab and dragging it to the middle-left edge of the main JupyterLab work area. A blue rectangle should preview the layout that you’ll get.
  3. Work through the notebook tutorial! After you “connect” the notebook to the WWT app, the app’s background will change due to some legacy-preserving behavior in pywwt. Run the code wwt.foreground_opacity = 0 in a new cell in order to keep the pywwt and the app more in sync.

If you have more time, check out some of the other sample notebooks! The Data Gallery collection includes a variety of other large FITS images that you can play with.

You can also go back to the tutorial landing page.

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