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Homework Help: Astronomy time required to capture exposures problem

  1. Feb 15, 2016 #1
    1. The problem statement, all variables and given/known data
    If you have a large telescope that has a 5 meter diameter with a field of view of 1 foot by 1 foot, and a small telescope with a diameter of 1 meter with a field of view of 1 degree by 1 degree, and your trying to take images of 30 quasars that has a limiting visual magnitude of 20 that are randomly distributed over a 5 degree by 5 degree field where it takes 10 minutes to capture a single quasar image. How long will it take for each telescope to take the image of the 30 quasars?

    2. Relevant equations
    For relevant equations, i'm not sure if these will help and really this is the part i'm having trouble with, trying to figure out what equations or if any I need any of these.
    • (soild angle) = area/(radius)^2
    • (Etendue) = A(mirror area) X (soild angle field of view)
    • SurveyTime is proportional to Field of View
    • SurveyTime is proportional to Field of View X collecting area = (Etendue)
    3. The attempt at a solution
    For the small telescope I have... Area = 0.785398 m^2 and for the large telescope...Area = 19.63 m^2, so from this I found that the area of the large telescope is 25 times the area of the small. I tryed to convert the field of view of the large telescopes feet to degrees and I got 0.016 degrees by 0.016 degrees. Im not sure how to use this information to find the actual time it will take each telescope to take the images of 30 quasars each taking 10 minutes a piece, any help would be much appreciated, thanks!
  2. jcsd
  3. Feb 20, 2016 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
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