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Homework Help: Signal to noise ratio and uncertainty in magnitude

  1. Dec 17, 2015 #1


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    • Poster has been reminded that they need to show their work
    1. The problem statement, all variables and given/known dat
    Show that if you have a signal f and noise σf for a stellar flux measurement, then the uncertainty on the observed magnitude is given by
    σm = 1.0875 x σf / f
    2. Relevant equations
    (you should use the fact that when ε<<1 then log(1±ε) ≈ ε/ln10 ).

    3. The attempt at a solution
  2. jcsd
  3. Dec 17, 2015 #2


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    Homework Helper

    You should show some attempt at the problem in this forum.
    Start with: let signal + noise be ##f + \sigma_f = f(1 + \frac{\sigma_f}{f} )##
    Do you know how to calculate the uncertainty?
  4. Dec 17, 2015 #3


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    Uncertainty in (1 + σf/f) = √((δσff)2 + (δf/f)2)
    or uncertainty in f + σf =√(δσf)2 + (δf)2
    Last edited: Dec 17, 2015
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