 ## SKYCALC Sky Model Calculator

 Sky Model Mode Version 2.0.9 Description FAQ

Optional Parameter Initialisation using Almanac Service

## The Cerro Paranal Advanced Sky Model

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

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
 sfu

### 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

 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

### 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) Calculate Atmosphere Temperature and Bolometric Radiance

 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).

 Send comments and questions via https://support.eso.org/