WEBTOP Exercise

In this exercise you will explore the resolution of two point sources using a circular aperture.  You can change the wavelength, aperture size, and angular separation of the sources in the usual way, by entering the values at the bottom of the screen and hitting "enter".  The display shows the image of the two sources (i.e. their combined point spread functions) and a plot of the intensity along a line joining the centers of the two Airy disks.  You may need to zoom out (using the zoom tool on the dashboard) in order to see the top of the intensity plot.  The minimum angular separation for resolution by the Rayleigh criterion is shown at the bottom right of the screen.  You get to WEBTOP by clicking  here .
 

• Pick a convenient size and wavelength (the defaults will do) and explore what happens as you change the angular separation of the sources.  Look at the image and the plot for separations at, below, and above the minimum Rayleigh criterion.
• Now set the separation at a value above the minimum and increase the wavelength.  Think about the implications of what you see for astronomical imaging in the IR, visible, UV, and radio wavelength ranges.  You may want to know that the conversion between radians and arc seconds is 1 rad = 2.06 x 10⁵ arc seconds.  The best resolution expected from the SOAR telescope that UNC is building in Chile is 0.3 arc seconds (in the visible, on a really good night).
• Finally, fix the wavelength and change the aperture size.  See why astronomers want larger and larger telescopes.  (They also need to collect more light from faint sources.) Given the size of aperture that WEBTOP allows, you might also want to think about the optics of the human eye. What happens as your pupil expands and contracts?