Sky Model Calculator

SKYCALC Sky Model Calculator

Sky Model Mode Version 2.0.9

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Optional Parameter Initialisation using Almanac Service

Site
	Observatory

Time
	UT	Time step forward/back
	MJD

Target
	Target coordinates from CDS Simbad searching by Name or ID:
	α ^° δ ^°

Sun




	Note: The Cerro Paranal Advanced Sky Model does not take telluric scattered sun light into account

Moon

Coordinate system: Projection: Milkyway

Sun and Moon symbols are not to scale. The red target symbol can be moved.

The Cerro Paranal Advanced Sky Model

Observatory Height above Sea Level

Altitude of Target above Horizon

alt=[19.5, 90]°
zenith distance z=0°

alt, z and x are coupled through the
plane parallel approximation x=sec(z),
z being the zenith distance z=90°−alt

Airmass

x = [1, 3]

Season and Period of Night

Season:

Night Period:

Precipitable Water Vapor

PWV = mm

Monthly Averaged Solar Radio Flux

sfu

Select Components to Include in the Radiance Model:

Scattered Moonlight
Note the following moon coordinate constraints: |z – z_moon| ≤ ρ ≤ |z + z_moon|
where ρ=moon/target separation, z=90°−alt and z_moon=90°−alt_moon

Sun-Moon Separation (Moon Phase)	[0,360]°	FLI = 0.500 (Half Moon Waxing )
Moon-Target Separation ( ρ )	[0,180]°
Moon Altitude over Horizon ( alt_moon )	[-90, 90]°	z_moon=45°
Moon-Earth Distance Normalised	[0.91, 1.08]

Scattered Starlight

Zodiacal Light

Heliocentric Ecliptic Longitude of Target		[-180, 180]°
Ecliptic Latitude of Target		[-90, 90]°

Molecular Emission of Lower Atmosphere

Emission Lines of Upper Atmosphere

Airglow/Residual Continuum

Instrumental Thermal Emission
This radiance component represents an instrumental effect. The emission is provided relative to the other model components. To obtain the correct absolute flux, an instrumental response curve must be applied to the resulting model spectrum (see section 6.2.4 in the documentation).

Element1 (e.g. Telescope)	T1 = K	Emissivity1 = [0,1[
Element2 (e.g. Instrument)	T2 = K	Emissivity2 = [0,1[
Element3 (e.g. Cryostat)	T3 = K	Emissivity3 = [0,1[

Wavelength Grid

Convolving Line Spread Function

	Vacuum
	Air (using the formula of Edlén 1966)

λmin= nm [ ≥ 300 nm]
λmax= nm [ ≤ 30,000 nm]

	Linear binning Δλ = nm/bin
	Logarithmic binning λ/Δλ = [≤ 10⁶]

None
Gaussian	FWHM=	bins
Boxcar	Width=	bins

Bins: 13863 bins

λ/Δλ : 20000 (max 1000000)

FITS file size: 0.77Mb (max 30 Mb)

Approx. response time: 3.2 s

Outputs

Plot Radiance Spectrum	Plot Radiance Components
Plot Transmission Spectrum	Plot Transmission Components

Calculate Broad-Band UBVRIZYJHKLMNQ magnitudes per arcsec²
Plot LSF Kernel (select an LSF kernel to enable this option)

SkyCalc is based on the Cerro Paranal Advanced Sky Model, which was developed in particular to be used in the ESO Exposure Time Calculators, by a team of astronomers at the Institute for Astro- and Particle Physics at the University of Innsbruck, as part of an Austrian in-kind contribution to ESO.

The in-kind contribution also includes two tools to correct observations for telluric absorption and emission (Molecfit and Skycorr), which can be found here.

The citations for the Cerro Paranal Sky Model are Noll et al. (2012, A&A 543, A92) and Jones et al. (2013, A&A 560, A91).

A library of telluric transmission spectra with various resolutions and atmospheric conditions has been calculated with the Cerro Paranal Advanced Sky Model. A description of the usage of the spectra can be found in the article Moehler et al. (2014, A&A 568, A9).