Compare the Crab Nebula expansion from years 1999 to 2012 RRS feed

  • General discussion

  • Import PMM561

    This program lets you align two images on top of each other, then animate them.  It was inspired from a recent Astronomy Picture of the Day

    I left a question in the code, and haven't figured out the answer yet.

    The Silverlight version's a bit goofed up, but more fun within SB since it gives you a much bigger window.

    • Edited by bigdaddyo Friday, September 13, 2013 3:20 AM
    Friday, September 13, 2013 3:19 AM

All replies

  • https ://

    showed up

    http ://

    (Sorry cant insert links)

    Friday, September 13, 2013 11:06 AM
  • I wanted to try to calculate it from the change in the two pictures, knowing the size (in the code) and that 13 years elapsed between the photos.
    Saturday, September 14, 2013 8:44 PM
  • Interesting program - Could line up the perimeter stars ok, but found it hard to see then which bit of the nebular belong to each image to judge the expansion.

    Then found the Space key does just what I need to see the differences.

    Saturday, September 14, 2013 9:03 PM
  • If I animate with space and stop it again, the opacity has some unknown value. It may be difficult to change the alignment then.

    Therefor I added a reset for opacitiy in the OnKey-subroutine:

    If GraphicsWindow.Lastkey="O" then



    You can then reset the opacity by pressing the o key.

    Jan [ WhTurner ] The Netherlands

    Sunday, September 15, 2013 10:46 AM
  • It's kinda tricky to align them isn't it.  Once you animate it, there's just a tiny difference in the outer edges, but must be a huge expansion velocity.
    • Edited by bigdaddyo Tuesday, September 17, 2013 4:27 AM
    Tuesday, September 17, 2013 4:26 AM