View the step-by-step solution to:


This question was created from Lab 05_Properties of Telescopes_2013.pdf


Light-gathering power of a telescope is directly proportional to the area of its primary lens or mirror. All lenses and mirrors have a
circular circumference. The area of a circle is given by the formula: A = 71:72. Because 1: is a constant, the radius, r, of the mirror or lens
is the most important factor in determining the light— gathering power of a telescope. Note that area of a circle varies by the square of the radius. Thus, a lens or mirror that is twice the radius (or diameter) of another telescope objective has 22 or 4 times the light—
gathering power. 1. A typical pair of binoculars has an objective lens of 50-mm diameter. A typical amateur telescope is an 8-inch reflector that has a
mirror diameter of 203 mm. (Give answers in a and b as a number; that is, When multiplying, use It as 3.14159.) (a) What is the light-collecting area of the 50-min objective? mm2 [Round to 1 decimal place[
(b) What is the light-collecting area of the 203-mm objective? mm2 [Round to 1 decimal place]
(c) The 203-mm objective collects times the light of a 50-mm objective. [Round to nearest whole number] (d) The brightness of celestial objects usually is expressed in terms of magnitude. A 1St magnitude star is defined as being 100
times brighter than a 6L11 magnitude star (5 magnitude steps). A single magnitude jump equals a brightness change of about
2.512 (given that 2.5125 = 100). Using the factor of 2.5 12 for a single magnitude jump, about how many magnitudes
fainter can the 203-mm objective “see” than the smaller 50-mm objective? [Round to nearest whole number] magnitudes [Hint:2.5121= 2.512; 2.5122 = ?; 2.5123 = ?; 2.5124 = ?; 2.5125 = 100]

Top Answer

(a) The light-collecting area of the 50-mm objective = 1 9 6 3 . 5 m m 2 (b) The... View the full answer

Sign up to view the full answer

Why Join Course Hero?

Course Hero has all the homework and study help you need to succeed! We’ve got course-specific notes, study guides, and practice tests along with expert tutors.

  • -

    Study Documents

    Find the best study resources around, tagged to your specific courses. Share your own to gain free Course Hero access.

    Browse Documents
  • -

    Question & Answers

    Get one-on-one homework help from our expert tutors—available online 24/7. Ask your own questions or browse existing Q&A threads. Satisfaction guaranteed!

    Ask a Question