- #1
BOYLANATOR
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Homework Statement
The 2-D image of a faint galaxy observed by a CCD covers 50 pixels. For an
exposure of 5 seconds a total of 10^4 photo-electrons are recorded by the CCD
from these pixels. An adjacent section of the CCD, covering 2500 pixels, records
the background sky count. During the same exposure time a total of 10^5 photoelectrons
are recorded from the adjacent section. Show that, after subtracting
the background sky count, the signal-to-noise ratio for the detection of the
galaxy is estimated to be 73.
Homework Equations
Average count rate = [itex]\hat{R}[/itex]=Nobs/t
σpoisson=√(Nobs)
The Attempt at a Solution
Number of photons per pixel per second due to galaxy + background + noise = 40
Number of photons per pixel per second due to background + noise = 8
So there 32 "signal" photons per second per pixel.
I am unsure how to calculate the average noise per pixel.
Any help is appreciated.