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NACO Exposure Time Calculator

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Infrared Adaptive Optics Spectroscopy Mode Version 6.0.0
Description.
F.A.Q
 
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Target Input Flux Distribution

Template Spectrum: Spectral Type (only JHK) Target Magnitude:
= Vega AB
Magnitudes are given per arcsec2 for extended sources.
MARCS Stellar Model:
Blackbody Temperature : K
Single Line
Lambda: nm
Flux: 10-16 ergs/s/cm2 (per arcsec2 for extended sources)
FWHM: nm

Spatial Distribution: Point Source Extended Source (per pixel)

Adaptive Optics Mode:

LGSLaser Guide Star
NGS

Natural Guide Star

Target / Reference Source
Separation: arcsec
Reference Source
V mag: Spectral Type

Sky Conditions

Airmass:
Seeing: arcsec FWHM in V-band at zenith (use this value in the proposal). The seeing is irrelevant for extended sources.
Probability 60% for a seeing smaller or equal to the requested value
A model of the AO-corrected PSF is used to define the S/N reference area. For details see the helpfile.
Choose Sky model (experimental)
Old ETC sky model (for comparison while testing)
The new Cerro Paranal advanced sky model

In this experimental version of the ETC, the parameters for the background contributions can be configured (only with the new sky model).

The default values in this experimental section are used in the normal (non-experimental) ETC.

The total background is modeled as a sum of contributions:

Btotal = ( Bsky + Btherm )   +   ( Aobj + Asky+ A?ext + A?int)

Bsky Background from the night sky as such. This is given by the new sky model with the normal parameters given in the Sky Conditions section above.
Btherm Instrumental thermal background contributions of different temperatures (T ≥ 0) and emissivities (0 ≤ ϵ < 1). See section 6.2.4 in the document Cerro Paranal advanced sky model.
Element1 (e.g. Telescope) T1 = K    ϵ1 =
Element2 (e.g. Instrument) T2 = K    ϵ2 =
Element3 (e.g. Cryostat) T3 = K    ϵ3 =


Aobj Additional background that is outside the telescope and with a signal proportional with the astronomical target.
Aobj = kobj · Fobj     , with kobj=
Asky Additional background that is outside the telescope and with a signal proportional with the sky background.
Asky = ksky · Bsky     , with ksky=
A?ext Additional external background from unknown origin that is outside the telescope
Constant: ph/s/cm2/A/arcsec2
Use the profile on the ETC server Contact Jakob (jvinther@eso.org) to discuss how to enable this option.
A?int Additional internal background from unknown origin, in unit electrons/pixel/s
Constant: e-/pixel/s
Use the profile on the ETC server Contact Jakob (jvinther@eso.org) to discuss how to enable this option.


Instrument Setup

NAOS WFS/Dichroic:
Dichroic Name Reflected light to the WFS
(Efficiency)
Transmitted light to CONICA
(Efficiency)
Conditions of use
VIS V,R,I [0.45 - 0.95] microns
(90%)
J,H,K,L,M [1.05 - 5.0] microns
(90%)
Near-IR observations
with optical WF sensing
N20C80 V,R,I,J,K [0.45 - 2.55] microns
(20%)
V,R,I,J,H,K [1.05 - 5.0] microns
(80%)
WF sensing and
observing in the IR
N90C10 V,R,I,J,K [0.45 - 2.55] microns
(90%)
V,R,I,J,H,K [1.05 - 5.0] microns
(10%)
WF sensing and
observing in the IR
JHK I,J,H,K [0.8 - 2.55] microns
(90%)
L,M [2.8 - 5.5] microns
(90%)
Thermal-IR observations
with WF sensing in the near-IR
K K [1.9 - 2.55] microns
(90%)
J,H [0.45 - 1.8] microns
(90%)
V,R,I,J,H observations
with WF sensing in K
FREE The NAOS-PS will try to find an optimal Dicroic/WFS combination. Note
Slit:
Grism/Filter Mode:
Instrument mode : (select Double_RdRstRd for LW).

Results

S/N ratio: S/N = DIT = sec Please note the relevant minimum DIT in the manual.
Exposure Time: NDIT =

The total exposure time is the product of DIT (Detector Integration Time) by NDIT (number of DITs). This exposure time does not take into account instrument and telescope overheads.


Plots: Toggle All / No Plots

Resultant spectrum including sky
Object Spectrum only
Sky Emission Spectrum
Sky Transmission Spectrum
S/N as a function of wavelength
Total Efficiency and Wavelength Range
Input spectrum in physical units
Point Spread Function (point source only)
Enslitted Energy (point source only)

Detailed S/N info
      

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