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Questions tagged [galsim]

GalSim, the modular galaxy image simulation toolkit

GalSim is open-source software for simulating images of astronomical objects (stars, galaxies) in a variety of ways. The bulk of the calculations are carried out in C++, and the user interface is in python. In addition, the code can operate directly on "config" files, for those users who prefer not to work in python.

The impetus for the software package was a weak lensing community data challenge, called GREAT3. However, the code has numerous additional capabilities beyond those needed for the challenge, and has been useful for a number of projects that needed to simulate high-fidelity galaxy images with accurate sizes and shears.

The code is available on GitHub, where you can download the code and find more information. The wiki page includes basic documentation and a set of examples that serve as an introductory tutorial.

Questions on StackOverflow tagged with galsim should generally be of the "How do I do this?" variety. If you find a bug in the code, please open an issue, rather than ask a question here.

28 questions
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installing Galsim on OSX with conda environment: fftw/tmv file failed to link correctly

I have installed fftw and boost with conda; conda install -c https://conda.anaconda.org/anaconda boost conda install -c https://conda.anaconda.org/nlesc fftw tmv with scons tmv0.72){58}> scons install PREFIX=/home/rgm/local the scons with the…
Richard McMahon
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Unable to get python include path python executable for GalSim

I am trying to install (update) my local version of GalSim software on Ubuntu 14.04 by running SCons. I have all the dependencies (boost, TMV etc.) installed and have used it for quite a while now. I use Python2.7. But now, when I run scons from the…
Arun Kannawadi
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Trouble Installing GalSim on OSX with Anaconda

I have been attempting to install GalSim on OSX 10.9 Mavericks with Anaconda installed and set as the default python, but have been running into the following error: Unable to build a python loadable module using the python executable: /usr/bin/env…
msprijatelj
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Inline display when using GalSim on iPython Notebook

It seems that all the demos write the image file to the system so that we can view it with DS9. Is there a way we can view the images we make inline on iPython Notebook, as we code? This would speed up my coding a lot. Thank you!
Gigi
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GALSIM: Using interpolated image class without specifying flux normalisation

For a project I am undertaking, I will need to calculate the derivative of a given surface brightness profile which is convolved with a pixel response function (as well as PSF etc.) For various reasons, but mainly for consistency, I wish to do this…
Christopher Duncan
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Deciphering errors regarding simultaneous fitting to galaxies in Galsim

I am fitting to galaxies in galsim and receive the following errors: File "/home/luis/Documents/SRC2014/galsim_work/noiseLibrary.py", line 50, in create_galaxy gal = gal.shear(g1=e1, g2=e2) File "/usr/lib/python2.7/dist-packages/galsim/base.py",…
alvarezcl
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FFT Runtime Error in Running Galsim

I keep receiving the following error when running a script to save an animation: RuntimeError: SB Error: fourierDraw() requires an FFT that is too large, 6144 If you can handle the large FFT, you may update gsparams.maximum_fft_size. So I went…
alvarezcl
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GalSim automatic image size behavior for galsim.GSObject.draw()

I've noticed that GSObject.draw can be called without the image keyword. The documentation says that an automatically sized image is returned if image = None. How exactly is this automatic size determined? Does it make sure to retain some fraction…
Eric Suchyta
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Interpolating PSF parameters with galsim

I'm hoping I can use Galsim to test various methods of PSF interpolation. I want to generate an image with galaxies, sample the PSF at various points and interpolate the PSF to the galaxy locations. The examples demonstrate how to generate a PSF at…
djbard
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Is there a way to get the galsim stamp size of a profile without computing the pixel table?

In galsim, I have created a galaxy with a given sersic profile. I convole it by a PSF. I would like to know if there is a way to get the size of the stamp that would be computed using drawImage without actually computing the pixels. Basically, I'd…
akira
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How to import angle values from a catalog into GalSim

I'm trying to import galaxy values (Sersic index, half light radius, etc) from an external ascii file in to GalSim. I'm having trouble reading in the position angle value 'beta', and would like to know if this is possible using the YAML format.…
Lee
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galsim galaxy simulation with (local wcs) PSF

I would like to use Galsim to simulate a set of galaxies convolved by PSFs. The galaxies are simple double sersic profiles that I create using the Sersic class from galsim (and then Shear to introduce some ellipticity). The PSFs I'like to use are…
akira
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Drawing an image of PSF with custom radial profile in GalSim

I have a radial profile of a point spread function (PSF) that I want to draw in GalSim, so that I can call FindAdaptiveMom on the resulting image. The profile is in units of normalized intensity vs. angular position in arcseconds. I have looked at…
Gigi
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Is the galsim boost dependency really needed?

I see that there is a noboost branch in the GalSim repository, but is there any reason why Boost is still being used in the main line? Would be very useful if you'd just get rid of the unnecessary and painful dependency. I'd be happy to do some…
Dale
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Atmosphere vs. AtmosphericScreen then PhaseScreenList

I'm trying to use the code provided in phase_screens.py that can reproduce the plot by Jee & Tyson (2011). When I try to run the line psf = atm.makePSF(lam = 700., exptime = 15., diam = 8.4, obscuration = .6) I get an AttributeError that says,…
Gigi
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