Parallax of asteroids JS9 (AiM) (Second Part - First Part)

     The thumb-jump:        Parallax angle:
  • Upload the images in the editing window:
    JS9-menu :   File ➔ open local ...
    Search the folder and activate images with [open].
  • JS9-menu :  View ➔ Blinking
    allows for a good overview of the images.
  • Check[ ✓ ] blink for every uploaded image.
  • Check [ ✓ ] Blink Images to see that the stars do not align perfectly.
  • Disable blinking images by unchecking [    ] Blink Images and [    ] blink.
  • Select the image of Cerro Tololo (lsc) because the asteroid is centered better in this image.
  • Use JS9-menu :   WCS ➔ wcs reproject ... ➔ all images in this display, using wcs
    to adapt the image of Teide (tfn) to the World Coordinat System-data.
    (Attention: Depending on the speed of your computer, this may take some time! )
  • By using the blinking-function ( [ ✓ ]! ) you can see the 'thumb-jump'.

  • Uncheck blinking: [    ] Blink Images and [    ] blink and close the blinking window.
  • The blending function allows the position of the asteroid to be seen in both images simultaneously:
    JS9-menu :  View ➔ Blending
  • Now you can measure the position of the asteroid:
    JS9-menu :  Analysis ➔ Region Stats in combination with
    JS9-menu :  Regions ➔ annulus.
  • Use the left mouse button to move the double circle over the 1st position of the asteroid and adjust the size of the inner circle to the size of the star discs.
    As long as the mouse pointer is in the editing field, you can use the cursor keys for precise adjustment.
  • In the "Region Stats(JS9)" window, read off the x1 and y1 position in the recording under "position".
  • Read off the x2 and y2 position in the recording in the same way.
  • Calculate how many pixels the two positions in x-direction and y-direction are apart.
    Δx = x2 - x1 ; Δy = y2 - y1
  • By using the pythagoraen theorem Δd² = Δx² + Δy² you can now determine the pixel distance Δd of the two positions.
  • 1 pixel corresponds to 0.571" for the 0.4m telescopes. Calculate the parallax angle!

  • You can use the zoom function to determine the position of the asteroid in the image more precisely.
  • You can move the bending image with the right mouse button. A short click on the right mouse button switches the shift function off again.
  • You can also drag the editing window at the bottom right corner to make it bigger.
  • Using a sketch, show that the distance between two points in the coordinate system can be calculated using the Pythagorean theorem.
  • Write down the calculation including the result.
  • Express the parallax angle in angular seconds and angular degrees.
  • Imagine that the triangle T1-T2-A between telescopes T1 and T2 and asteroid A is isosceles:
    Make a sketch and draw the height to point A.
  • The distance between Cerro Tololo (telescope 1) and Teide (telescope 2) is 8032km. You have already measured the parallax angle of asteroid A.
    Using a trigonometric function (sine, cosine, tangent), calculate the distance of the asteroid from the observation points T1 or T2.
  • Is the assumption of an isosceles triangle T1-T2-A sufficiently valid here?
  • Add the table "Science Imagers" from the LCO page to your elaboration. Explain the meaning of the individual columns for the 0.4m telescope used here.

The JS9 application was taken from CENTER FOR ASTROPHYSICS|HARVARD AND SMITHSONIAN and was didactically simplified by us:
The programme is subject to the MIT licence. Source code @GitHub
Astronomy and internet in Münster (AiM):