20081014

Astronomy midterm question: (non-)improvement in telescope powers?

Astronomy 210 Midterm 1, fall semester 2008
Cuesta College, San Luis Obispo, CA

Suppose that there is no turbulence in the upper atmosphere above San Luis Obispo, CA. If a telescope is used that evening, discuss which powers (light-gathering, resolving, magnifying) would not be improved because of this weather phenomenon, and explain why.

Solution and grading rubric:
  • p:
    Correct. Light-gathering power depends on the area of the primary lens or mirror, limited by light pollution; resolving power depends on the width of the primary lens or mirror, limited by atmospheric seeing conditions (turbulence); magnifying power depends on the focal lengths of the primary lens or mirror and eyepiece lens. Resolving power will be improved. Discusses light-gathering power and magnifying power as not being improved by no turbulence. (May debate magnifying power improving in that the maximum useful magnification is improved, although the factor that images are magnified is unchanged).
  • r:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Resolving power improved as in (p), but only one of light-gathering power or magnifying power as not improving.
  • t:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Claims resolving power (in addition to either light-gathering power or magnifying power) would not be improved by lack of turbulence.
  • v:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  • x:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Section 70160
p: 8 students
r: 17 students
t: 7 students
v: 1 student
x: 0 students
y: 1 student
z: 0 students

A sample "p" response (from student 8187):

Another "p" response (from student 9387):

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