Questions

1. For a parabolic mirror 1 meter in diameter with a focal length of 4 meters, what is the diameter of the ``Airy'' disk, the diffraction disk inside the first minimum of the diffraction pattern? Give your answer in seconds of arc on the sky, and in microns ($10^{-6}$ meter) in the focal plane. You should do this calculation using an expression for the diffraction pattern of a circular aperature, and then verify it with OSLO.
2. How far off the optical axis can a star be, and still have coma less than the size of the Airy disk? This is the diffraction-limited field of view.
3. How large is the coma 15 minutes of arc, 1/4 degree, off axis?
4. Change this mirror to a spherical mirror. What is the size of the best image on axis, again in seconds of arc and in microns? What can you conclude about the choice of the shape of a mirror surface on the performance of a telescope?
5. Start OSLO again, but this time with the Hubble Telescope model.
6. What is the primary mirror diameter, and what are the shapes of the primary and the secondary mirrors here?
7. Answer questions 1-3 above, but now for this system.
8. Assuming that the telescope is perfectly made and that it is used to observe a nearby red giant star 2 astronomical units in diameter, how close would that star have to be for it to appear larger than the Airy disk?
9. Are there any red giants that close? (Use the web or resources of your own choice to find the distances to the nearest stars.)