Exposure Time Calculator 2.9
NOTCAM IR imaging WF
NOTCAM IR imaging HR
NOTCAM IR spectroscopy WF
NOTCAM IR spectroscopy HR
Grism / Fiber
Slitwidth / Fiber diameter "
- - - - -
Single Exp. Time (sec)
Number of Exposures
(D, G or B for typical dark, grey or bright)
S/N vs. Exptime
S/N vs. Magnitude
Peak vs. Exptime
The ETC does not yet support 'extended sources' for FIES
ALFOSC seeing measurements
The ETC uses the following default values for atmospheric extinction: U=0.55, B=0.25, V=0.15, R=0.09, I=0.06, Z=0.05, Y=0.07, J=0.09, H=0.07, Ks=0.08 mag/airmass.
Use extinction=0 for the ETC to use these values.
Darkest La Palma sky: U=22, B=22.7, V=21.9, R=21.0, I=20.
Use sky-brightness=0 for the ETC to use these values.
Moonlight brightens the sky by about 1 mag (first/last quarter) to 4 mag (full moon) in UBV.
In I the full moon brightens the sky about 2 mag.
The sky level in the near-IR is temporally and spatially variable due to airglow and thermal emission The ETC uses these standard magnitudes: J=15.6, H=13.9, Ks=13.2
The calculation is based on the SIGNAL program, kindly provided by Chris Benn (ING). Information and guidelines of usage can be found
S/N estimate includes the object photon noise, sky photon noise and the readout noise. In the case of multiple frames, average combining is assumed for the readout noise.
Peak counts in the imaging mode for a point source are calculated assuming a 2-D gaussian point spread function for the point source.
Peak counts in the spectroscopy mode are calculated assuming a gaussian profile for the spectrum.
Back to top
Last modified: November 04 2021