User Manual
Doc. Number: ESO-323064
Doc. Version: 2
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These features can be removed by dividing the solar analogue spectrum by the solar
spectrum at the resolution of the observations.
5.2.6.4 Catalogues
The CRIRES tools web page
http://www.eso.org/instruments/crires/tools
of catalogues listing suitable telluric and spectrophotometric standards.
5.3 The Exposure Time Calculator
The CRIRES
exposure time calculator can be found at:
http://www.eso.org/observing/etc/
The ETC returns an estimate of the on-source exposure time necessary to achieve the
requested Signal-to-Noise Ratio (SNR) given the
Target
properties, the
Instrument
setup
and the constrains set, i.e.,
Sky
,
Seeing
and IQ
(see Figure 33).
A detailed description of all ETC input and output parameters is given on the
however below we provide some general guidelines, and advise on the main ETC features.
Figure 33: Screenshot of the CRIRES ETC
Exp.Time
tab. User requests the desired SNR
by using a given DIT and the ETC returns the total exposure time (DITxNDIT) needed.
Target
tab:
•
The target input magnitude can be specified for a point or an extended source. For
the latter, the input parameter corresponds to the magnitude per square arcseconds.
Also input flux can be specified as surface brightness. If the
Emission line
option is
chosen, it corresponds either to the total line flux, for a point source, or to the surface
brightness for an extended source.