Set 1: SkyMaker simulation information
STEP home Simulations Data Mailing List


These simulations can be downloaded from the University of British Columbia from The input catalogues can also be downloaded from here.

Each simulation set is an ensemble of 64 4096x4096 pixels images. Expect a total of roughly 2e5 galaxies for each set, which allows a shear statistical uncertainty of ~1e-3. Each set has been done with a fixed PSF and fixed shear strength (see details below). There are 6 types of PSF (ranging from psf0 to psf5) and 5 types of shear (lens0 to lens4) so far. In each set, each image is identified with a number ranging from 1 to 64. For a given image number, the galaxies and stars are UNCHANGED (same location, unlensed orientation, mag, profil, etc...) for different PSF and shears.
Any comments/questions: waerbeke[at]

Directory tree:

STEPimages ---> psf0lens0 ---> STEPimage.1.psf0.lens0.fits
psf0lens1 ---> STEPimage.*.psf0.lens1.fits

Contains galaxies for image number 1 to 64. format is:

200 155.598 1954.978 20.3004 0.191 0.252 0.798 84.68 0.704 0.761 79.03 0.61757

bulge: de vaucouleur
disk: exp(-sqrt(x^2+y^2)/rg) cut at 4rg

200: code
155.598 1954.978: X and Y
20.3004: total mag
0.191: bulge to total flux ratio
0.252: bulge length scale (arcsec)
0.798: bulge projected axis ratio
84.68: bulge position angle
0.704: disk length scale (arcsec)
0.761: disk projected axis ratio
79.03: disk position angle
0.61757: redshift

Contains all stars, format is:

100 434.089 2588.512 24.7552

100: code
434.089 2588.512: X and Y
24.7552: magnitude

CCD, noise and sky properties:

CCD gain is 2 e-/ADU
Readout noise is 2 e-/ADU
exposure time is 3600 sec.
mag_zero is 26.5
background sky is 19.2 (CFHT site, I band)
pixel scale is 0.206 arcsecs

Telescope pupil (CFHT config):

primary diameter 3.5m
secondary diameter 1m
4 arms 1cm thick (30 degres oriented)

Lensing strengths:
We encourage the blind analysis of these simulations. After you have analysed the simulations, the lensing strengths can be found in the in the STEP simulation report

lens0: e1=? e2=?
lens1: e1=? e2=?
lens2: e1=? e2=?
lens3: e1=? e2=?
lens4: e1=? e2=?

PSF types:
psf0: seeing=0.9 no anisotropy
psf1: seeing=0.7 coma in arcsec (0.4 0.3)
psf2: seeing=0.7 jitter in arcsec (major axis 0.4 minor axis 0.3 angle +30)
psf3: seeing=0.7 defocusing 0.4 arcsec
psf4: seeing=0.7 astigmatism in arcsec (0.4 0.3)
psf5: seeing=0.7 triangular PSF in arcsec (0.4 0.3)

Note that the equivalent seeing for psf1 to 5 is roughly 0.8-0.9 (which is comparable to the image quality in psf0)

SkyMaker stuff configuration file
Download the stuff configuration file here


Last modified 29th Mar.
SkyMaker simulations made available by Ludovic Van Waerbeke, waerbeke[at]