Astronomy midterm question: telescope advantage comparison

Astronomy 210 Midterm 1, fall semester 2013
Cuesta College, San Luis Obispo, CA

The primary mirror diameters and tube lengths of two different telescopes are measured, and their telescope powers are discussed by two astronomy students. Both telescopes use the same eyepieces.

Student 1: The Newtonian reflector is better at producing images with finer details.
Student 2: The Schmidt-Cassegrain reflector is better at looking at faint objects.

Discuss which of these students you disagree with, and why. Support your answer using the properties of telescopes and telescope powers.

Solution and grading rubric:

• p:
  Discusses how diameter of primary mirror determines both light-gathering power and resolving power, such that a larger diameter mirror of the Schmidt-Cassegrain telescope would result in making fainter objects brighter, and allowing finer details to be seen, thus the first student's statement is incorrect.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
• t: Contains right ideas, but discussion is unclear/incomplete or contains major errors.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion of telescope parameters and telescope powers is garbled.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Does not discuss connection between telescope parameters and telescope powers.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 70158
Exam code: midterm1s73W
p: 19 students
r: 7 students
t: 12 students
v: 8 students
x: 4 students
y: 0 students
z: 0 students

Section 70160
Exam code: midterm1N1t3
p: 11 students
r: 1 student
t: 11 students
v: 5 students
x: 1 student
y: 0 students
z: 0 students

A sample "p" response (from student 4846):

Another sample "p" response (from student 6683):