# Signal to noise ratio and uncertainty in magnitude

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1. Dec 17, 2015

### CGM

• 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. Dec 17, 2015

### RUber

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?

3. Dec 17, 2015

### CGM

Uncertainty in (1 + σf/f) = √((δσff)2 + (δf/f)2)
?
or uncertainty in f + σf =√(δσf)2 + (δf)2

Last edited: Dec 17, 2015