SKYCALC Sky Model Calculator

Sky Model Mode Version 2.0.0
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SkyCalc Sky Model Calculator

Optional Parameter Initialisation using Almanac Service

The Cerro Paranal Advanced Sky Model

Observatory Height above Sea Level New option!
Altitude of Target above Horizon alt=[19.5, 90]°

alt, z and 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  (Paranal median ≈ 2.5mm)
Monthly Averaged Solar Radio Flux

Select Components to Include in the Radiance Model:

Note the following moon coordinate constraints: |z – zmoon| ≤ ρ ≤ |z + zmoon|
where ρ=moon/target separation, z=90°−alt and zmoon=90°−altmoon
Sun-Moon Separation (Moon Phase) [0,360]° FLI = 0.50
Moon-Target Separation   ( ρ ) [0,180]°
Moon Altitude over Horizon ( altmoon )
[-90, 90]°
Moon-Earth Distance Normalised [0.91, 1.08]
Heliocentric Ecliptic Longitude of Target [-180, 180]°
Ecliptic Latitude of Target [-90, 90]°

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 (in Vacuum)

Convolving Line Spread Function

λmin= nm [ ≥ 300 nm]
λmax= nm [ ≤ 30,000 nm]
[≤ 106]
FWHM= bins
Width= bins


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).