{
  "id": 71343,
  "title": "Is flux normalized for a pass band filter profile?",
  "url": "/competitions/PLAsTiCC-2018/discussion/71343",
  "author_name": "",
  "post_date": "2018-11-12T19:51:22.384445100Z",
  "votes": 1,
  "comment_count": 10,
  "views": 0,
  "content": "<p>The passband filters have different opacity, is flux normalized to take it into account ? Also, for a given object is the reference image the same across all pass bands? What it the spectral profile of the reference image, does it mimic black-body radiation?</p>",
  "messages": [
    {
      "id": "419943",
      "postDate": "11/12/2018 19:51:22",
      "content": "<p>The passband filters have different opacity, is flux normalized to take it into account ? Also, for a given object is the reference image the same across all pass bands? What it the spectral profile of the reference image, does it mimic black-body radiation?</p>",
      "rawMarkdown": "The passband filters have different opacity, is flux normalized to take it into account ? Also, for a given object is the reference image the same across all pass bands? What it the spectral profile of the reference image, does it mimic black-body radiation?",
      "votes": null
    },
    {
      "id": "419960",
      "postDate": "11/12/2018 20:54:12",
      "content": "<blockquote>\n  <p>Also, for a given object is the reference image the same across all pass bands?</p>\n</blockquote>\n\n<p>No, each PB has it's own template.</p>\n\n<blockquote>\n  <p>What it the spectral profile of the reference image, does it mimic black-body radiation?</p>\n</blockquote>\n\n<p>Since the pre-survey image might contain a flux brighter than its true zero leading to a negative flux, I'd assume no</p>",
      "rawMarkdown": "&gt;  Also, for a given object is the reference image the same across all pass bands?\n\nNo, each PB has it's own template.\n\n&gt; What it the spectral profile of the reference image, does it mimic black-body radiation?\n\nSince the pre-survey image might contain a flux brighter than its true zero leading to a negative flux, I'd assume no",
      "votes": null
    },
    {
      "id": "420002",
      "postDate": "11/12/2018 22:55:17",
      "content": "<p><code>No, each PB has it's own template</code> -- is it from the starter document?did not notice it...  </p>",
      "rawMarkdown": "```No, each PB has it's own template``` -- is it from the starter document?did not notice it...",
      "votes": null
    },
    {
      "id": "420015",
      "postDate": "11/12/2018 23:28:25",
      "content": "<p>One of the official LSST folks commented on a thread a while back; I can't find it now, but I'm certain I recall the testimony accurately :-).</p>",
      "rawMarkdown": "One of the official LSST folks commented on a thread a while back; I can't find it now, but I'm certain I recall the testimony accurately :-).",
      "votes": null
    },
    {
      "id": "420057",
      "postDate": "11/13/2018 01:46:51",
      "content": "<p>Authman is correct - each passband has it's own reference image. The reference image is also a real image, just like the rest of the measurements. The passband profile for the reference images is the same as the rest of the observations if that is what you mean by spectral profile. Astronomers normally refer to spectral profiles (or more precisely spectral energy distributions or SEDs) of sources, not the passbands. Each image has several tens of thousands of sources, each with their own spectral profile/SED. </p>\n\n<p>A more helpful statement might be that you don't need to worry about the properties of the template image for this challenge. We have not included them with the metadata.</p>\n\n<p>Cheers,</p>\n\n<p>-Gautham for the PLAsTiCC team</p>",
      "rawMarkdown": "Authman is correct - each passband has it's own reference image. The reference image is also a real image, just like the rest of the measurements. The passband profile for the reference images is the same as the rest of the observations if that is what you mean by spectral profile. Astronomers normally refer to spectral profiles (or more precisely spectral energy distributions or SEDs) of sources, not the passbands. Each image has several tens of thousands of sources, each with their own spectral profile/SED. \n\nA more helpful statement might be that you don't need to worry about the properties of the template image for this challenge. We have not included them with the metadata.\n\nCheers,\n\n-Gautham for the PLAsTiCC team",
      "votes": null
    },
    {
      "id": "420076",
      "postDate": "11/13/2018 02:44:38",
      "content": "<p>is the flux same as apparent magnitude?</p>",
      "rawMarkdown": "is the flux same as apparent magnitude?",
      "votes": null
    },
    {
      "id": "420087",
      "postDate": "11/13/2018 03:18:20",
      "content": "<p>The flux is the difference between measured brightness and a reference brightness.  Apparent magnitude is a log transform of the measured brightness.  Therefore flux and magnitude are not the same.</p>",
      "rawMarkdown": "The flux is the difference between measured brightness and a reference brightness.  Apparent magnitude is a log transform of the measured brightness.  Therefore flux and magnitude are not the same.",
      "votes": null
    },
    {
      "id": "420125",
      "postDate": "11/13/2018 05:13:55",
      "content": "<p>thanks @CPMP. i am generating features and happen to get confused with how to properly augment the flux. but i think i got it now, thanks to all your replies.</p>",
      "rawMarkdown": "thanks @CPMP. i am generating features and happen to get confused with how to properly augment the flux. but i think i got it now, thanks to all your replies.",
      "votes": null
    },
    {
      "id": "420245",
      "postDate": "11/13/2018 10:37:09",
      "content": "<p>No pb.  This took time to grasp for me too!</p>",
      "rawMarkdown": "No pb.  This took time to grasp for me too!",
      "votes": null
    },
    {
      "id": "420251",
      "postDate": "11/13/2018 10:53:16",
      "content": "<p><code>Astronomers normally refer to spectral profiles (or more precisely spectral energy distributions or SEDs) of sources, not the passbands</code> -- yes, that's what I meant, as I understood for the reference you use the image of the known source; it would be nice to know it's light curve or SED, but as they are different for each pass band and each part of the sky, then it would not work out. Good to know each spectral part has a different reference, it explains my observations in experiments</p>",
      "rawMarkdown": "```Astronomers normally refer to spectral profiles (or more precisely spectral energy distributions or SEDs) of sources, not the passbands``` -- yes, that's what I meant, as I understood for the reference you use the image of the known source; it would be nice to know it's light curve or SED, but as they are different for each pass band and each part of the sky, then it would not work out. Good to know each spectral part has a different reference, it explains my observations in experiments",
      "votes": null
    },
    {
      "id": "420269",
      "postDate": "11/13/2018 11:28:24",
      "content": "<p>BTW, when the different between reference and object is over 3 sigma, what is sigma?</p>",
      "rawMarkdown": "BTW, when the different between reference and object is over 3 sigma, what is sigma?",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 419960,
      "author_name": "authman",
      "author_url": "",
      "post_date": "11/12/2018 20:54:12",
      "content": "<blockquote>\n  <p>Also, for a given object is the reference image the same across all pass bands?</p>\n</blockquote>\n\n<p>No, each PB has it's own template.</p>\n\n<blockquote>\n  <p>What it the spectral profile of the reference image, does it mimic black-body radiation?</p>\n</blockquote>\n\n<p>Since the pre-survey image might contain a flux brighter than its true zero leading to a negative flux, I'd assume no</p>",
      "votes": null,
      "replies": [
        {
          "id": 420002,
          "author_name": "blondinka",
          "author_url": "",
          "post_date": "11/12/2018 22:55:17",
          "content": "<p><code>No, each PB has it's own template</code> -- is it from the starter document?did not notice it...  </p>",
          "votes": null,
          "replies": []
        },
        {
          "id": 420015,
          "author_name": "authman",
          "author_url": "",
          "post_date": "11/12/2018 23:28:25",
          "content": "<p>One of the official LSST folks commented on a thread a while back; I can't find it now, but I'm certain I recall the testimony accurately :-).</p>",
          "votes": null,
          "replies": []
        }
      ]
    },
    {
      "id": 420057,
      "author_name": "gsnarayan",
      "author_url": "",
      "post_date": "11/13/2018 01:46:51",
      "content": "<p>Authman is correct - each passband has it's own reference image. The reference image is also a real image, just like the rest of the measurements. The passband profile for the reference images is the same as the rest of the observations if that is what you mean by spectral profile. Astronomers normally refer to spectral profiles (or more precisely spectral energy distributions or SEDs) of sources, not the passbands. Each image has several tens of thousands of sources, each with their own spectral profile/SED. </p>\n\n<p>A more helpful statement might be that you don't need to worry about the properties of the template image for this challenge. We have not included them with the metadata.</p>\n\n<p>Cheers,</p>\n\n<p>-Gautham for the PLAsTiCC team</p>",
      "votes": null,
      "replies": [
        {
          "id": 420076,
          "author_name": "niclasdoce",
          "author_url": "",
          "post_date": "11/13/2018 02:44:38",
          "content": "<p>is the flux same as apparent magnitude?</p>",
          "votes": null,
          "replies": []
        },
        {
          "id": 420087,
          "author_name": "cpmpml",
          "author_url": "",
          "post_date": "11/13/2018 03:18:20",
          "content": "<p>The flux is the difference between measured brightness and a reference brightness.  Apparent magnitude is a log transform of the measured brightness.  Therefore flux and magnitude are not the same.</p>",
          "votes": null,
          "replies": []
        },
        {
          "id": 420125,
          "author_name": "niclasdoce",
          "author_url": "",
          "post_date": "11/13/2018 05:13:55",
          "content": "<p>thanks @CPMP. i am generating features and happen to get confused with how to properly augment the flux. but i think i got it now, thanks to all your replies.</p>",
          "votes": null,
          "replies": []
        },
        {
          "id": 420245,
          "author_name": "cpmpml",
          "author_url": "",
          "post_date": "11/13/2018 10:37:09",
          "content": "<p>No pb.  This took time to grasp for me too!</p>",
          "votes": null,
          "replies": []
        },
        {
          "id": 420251,
          "author_name": "blondinka",
          "author_url": "",
          "post_date": "11/13/2018 10:53:16",
          "content": "<p><code>Astronomers normally refer to spectral profiles (or more precisely spectral energy distributions or SEDs) of sources, not the passbands</code> -- yes, that's what I meant, as I understood for the reference you use the image of the known source; it would be nice to know it's light curve or SED, but as they are different for each pass band and each part of the sky, then it would not work out. Good to know each spectral part has a different reference, it explains my observations in experiments</p>",
          "votes": null,
          "replies": []
        },
        {
          "id": 420269,
          "author_name": "blondinka",
          "author_url": "",
          "post_date": "11/13/2018 11:28:24",
          "content": "<p>BTW, when the different between reference and object is over 3 sigma, what is sigma?</p>",
          "votes": null,
          "replies": []
        }
      ]
    }
  ],
  "raw_markdown_by_id": {
    "419943": "The passband filters have different opacity, is flux normalized to take it into account ? Also, for a given object is the reference image the same across all pass bands? What it the spectral profile of the reference image, does it mimic black-body radiation?",
    "419960": "&gt;  Also, for a given object is the reference image the same across all pass bands?\n\nNo, each PB has it's own template.\n\n&gt; What it the spectral profile of the reference image, does it mimic black-body radiation?\n\nSince the pre-survey image might contain a flux brighter than its true zero leading to a negative flux, I'd assume no",
    "420002": "```No, each PB has it's own template``` -- is it from the starter document?did not notice it...",
    "420015": "One of the official LSST folks commented on a thread a while back; I can't find it now, but I'm certain I recall the testimony accurately :-).",
    "420057": "Authman is correct - each passband has it's own reference image. The reference image is also a real image, just like the rest of the measurements. The passband profile for the reference images is the same as the rest of the observations if that is what you mean by spectral profile. Astronomers normally refer to spectral profiles (or more precisely spectral energy distributions or SEDs) of sources, not the passbands. Each image has several tens of thousands of sources, each with their own spectral profile/SED. \n\nA more helpful statement might be that you don't need to worry about the properties of the template image for this challenge. We have not included them with the metadata.\n\nCheers,\n\n-Gautham for the PLAsTiCC team",
    "420076": "is the flux same as apparent magnitude?",
    "420087": "The flux is the difference between measured brightness and a reference brightness.  Apparent magnitude is a log transform of the measured brightness.  Therefore flux and magnitude are not the same.",
    "420125": "thanks @CPMP. i am generating features and happen to get confused with how to properly augment the flux. but i think i got it now, thanks to all your replies.",
    "420245": "No pb.  This took time to grasp for me too!",
    "420251": "```Astronomers normally refer to spectral profiles (or more precisely spectral energy distributions or SEDs) of sources, not the passbands``` -- yes, that's what I meant, as I understood for the reference you use the image of the known source; it would be nice to know it's light curve or SED, but as they are different for each pass band and each part of the sky, then it would not work out. Good to know each spectral part has a different reference, it explains my observations in experiments",
    "420269": "BTW, when the different between reference and object is over 3 sigma, what is sigma?"
  },
  "source": "meta"
}