Galsim-Galaxy.ipynb

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    "# Copyright (c) 2012-2018 by the GalSim developers team on GitHub\n",
    "# https://github.com/GalSim-developers\n",
    "#\n",
    "# This file is part of GalSim: The modular galaxy image simulation toolkit.\n",
    "# https://github.com/GalSim-developers/GalSim\n",
    "#\n",
    "# GalSim is free software: redistribution and use in source and binary forms,\n",
    "# with or without modification, are permitted provided that the following\n",
    "# conditions are met:\n",
    "#\n",
    "# 1. Redistributions of source code must retain the above copyright notice, this\n",
    "#    list of conditions, and the disclaimer given in the accompanying LICENSE\n",
    "#    file.\n",
    "# 2. Redistributions in binary form must reproduce the above copyright notice,\n",
    "#    this list of conditions, and the disclaimer given in the documentation\n",
    "#    and/or other materials provided with the distribution.\n",
    "#\n",
    "\"\"\"\n",
    "COPY OF Demo #1\n",
    "​\n",
    "This is the first script in our tutorial about using GalSim in python scripts: examples/demo*.py.\n",
    "(This file is designed to be viewed in a window 100 characters wide.)\n",
    "​\n",
    "Each of these demo*.py files are designed to be equivalent to the corresponding demo*.yaml file\n",
    "(or demo*.json -- found in the json directory).  If you are new to python, you should probably\n",
    "look at those files first as they will probably have a quicker learning curve for you.  Then you\n",
    "can look through these python scripts, which show how to do the same thing.  Of course, experienced\n",
    "pythonistas may prefer to start with these scripts and then look at the corresponding YAML files.\n",
    "​\n",
    "To run this script, simply write:\n",
    "​\n",
    "    python demo1.py\n",
    "​\n",
    "​\n",
    "This first script is about as simple as it gets.  We draw an image of a single galaxy convolved\n",
    "with a PSF and write it to disk.  We use a circular Gaussian profile for both the PSF and the\n",
    "galaxy, and add a constant level of Gaussian noise to the image.\n",
    "​\n",
    "In each demo, we list the new features introduced in that demo file.  These will differ somewhat\n",
    "between the .py and .yaml (or .json) versions, since the two methods implement things in different\n",
    "ways.  (demo*.py are python scripts, while demo*.yaml and demo*.json are configuration files.)\n",
    "​\n",
    "New features introduced in this demo:\n",
    "​\n",
    "- obj = galsim.Gaussian(flux, sigma)\n",
    "- obj = galsim.Convolve([list of objects])\n",
    "- image = obj.drawImage(scale)\n",
    "- image.added_flux  (Only present after a drawImage command.)\n",
    "- noise = galsim.GaussianNoise(sigma)\n",
    "- image.addNoise(noise)\n",
    "- image.write(file_name)\n",
    "- image.FindAdaptiveMom()\n",
    "\"\"\"\n",
    "\n",
    "import sys\n",
    "import os\n",
    "import math\n",
    "import logging\n",
    "import galsim\n",
    "\n",
    "    \"\"\"\n",
    "    About as simple as it gets:\n",
    "      - Use a circular Gaussian profile for the galaxy.\n",
    "      - Convolve it by a circular Gaussian PSF.\n",
    "      - Add Gaussian noise to the image.\n",
    "    \"\"\"\n",
    "    # In non-script code, use getLogger(__name__) at module scope instead.\n",
    "    logging.basicConfig(format=\"%(message)s\", level=logging.INFO, stream=sys.stdout)\n",
    "    logger = logging.getLogger(\"simplegalaxy\")\n",
    "\n",
    "    gal_flux = 2.e5    # total counts on the image\n",
    "    gal_sigma = 0.2     # arcsec\n",
    "    psf_sigma = 0.01     # arcsec\n",
    "    pixel_scale = 0.2  # arcsec / pixel\n",
    "    noise = 30.        # standard deviation of the counts in each pixel\n",
    "\n",
    "    logger.info('Starting simplegalaxy using:')\n",
    "    logger.info('    - circular Gaussian galaxy (flux = %.1e, sigma = %.1f),',gal_flux,gal_sigma)\n",
    "    logger.info('    - circular Gaussian PSF (sigma = %.1f),',psf_sigma)\n",
    "    logger.info('    - pixel scale = %.2f,',pixel_scale)\n",
    "    logger.info('    - Gaussian noise (sigma = %.2f).',noise)\n",
    "\n",
    "    # Define the galaxy profile\n",
    "    gal = galsim.Gaussian(flux=gal_flux, sigma=gal_sigma)\n",
    "    logger.debug('Made galaxy profile')\n",
    "\n",
    "    # Define the PSF profile\n",
    "    psf = galsim.Gaussian(flux=1., sigma=psf_sigma) # PSF flux should always = 1\n",
    "    logger.debug('Made PSF profile')\n",
    "\n",
    "    # Final profile is the convolution of these\n",
    "    # Can include any number of things in the list, all of which are convolved\n",
    "    # together to make the final flux profile.\n",
    "    final = galsim.Convolve([gal, psf])\n",
    "    logger.debug('Convolved components into final profile')\n",
    "\n",
    "    # Draw the image with a particular pixel scale, given in arcsec/pixel.\n",
    "    # The returned image has a member, added_flux, which is gives the total flux actually added to\n",
    "    # the image.  One could use this value to check if the image is large enough for some desired\n",
    "    # accuracy level.  Here, we just ignore it.\n",
    "    image = final.drawImage(scale=pixel_scale)\n",
    "    #image = final.drawImage(scale=pixel_scale, method = \"phot\", save_photons=True)\n",
    "    logger.debug('Made image of the profile: flux = %f, added_flux = %f',gal_flux,image.added_flux)\n",
    "\n",
    "    # Add Gaussian noise to the image with specified sigma\n",
    "    image.addNoise(galsim.GaussianNoise(sigma=noise))\n",
    "    logger.debug('Added Gaussian noise')\n",
    "\n",
    "    # Add sensor effects\n",
    "    sensor = galsim.SiliconSensor(strength = 1.0, diffusion_factor=100, nrecalc=10000)\n",
    "    photons = galsim.PhotonArray(100000)\n",
    "    sensor.accumulate(photons, image.view())\n",
    "\n",
    "    # Write the image to a file\n",
    "    if not os.path.isdir('output'):\n",
    "        os.mkdir('output')\n",
    "    file_name = os.path.join('output','simplegalaxy.fits')\n",
    "    # Note: if the file already exists, this will overwrite it.\n",
    "    image.write(file_name)\n",
    "\n",
    "    results = image.FindAdaptiveMom()\n",
    "\n"
   ]
  }
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