MOSFIRE *UNVERIFIED* Exposure Time Calculator
The following table summarizes the expected spectral resolution R
(λ/Δλ), and S/N ratio in the best quartiles
(25%, 50%, 75%, and 100%). To get a sense for the number of total detected
photons an example wavelength
is selected in each band near the median signal-to-noise ratio. Note
that the values are summed over exposures assuming Poisson statistics.
The total number of photons from the object and sky are computed in a resolution
element at the example wavelength. Note that A/B subtraction is
assumed and accounted for in the s/n calculation.
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Y |
J |
H |
K |
| Typ. Slit-Limited R: |
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| S/N Quartiles: |
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| λexample: |
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Detector noise per resolution element includes a
read-noise of
and dark-current
shot-noise of
.
Note that
Total RN=RN
pixel · (N
pix
· N
pairs · 2)
1/2
The slit and extraction diameter subtend .
Extraction losses for the slit width and seeing amount to
.
Plots
Detected Signal to Noise Ratio
per Resolution Element
S/N
Detected Photons per resolution element
in a single exposure. Bottom horizontal lines indicate total read noise and dark current (in
photons). Top horizontal lines indicate where the detector becomes
one-percent non linear or saturated.
Counts
Emitted AB Magnitude SED of
object and Sky for the given slit and seeing.
The SEDs
Throughput (Sky, Slit, Optics,
and Detector)
MOSFIRE's Throughput as a function of wavelength