{
  "id": 67944,
  "title": "Flux or Flux difference?",
  "url": "/competitions/PLAsTiCC-2018/discussion/67944",
  "author_name": "",
  "post_date": "2018-10-07T15:56:12.097905700Z",
  "votes": 3,
  "comment_count": 2,
  "views": 0,
  "content": "<p>Are the flux values really some sort of flux difference from a \"baseline\" value that is different for each object?</p>",
  "messages": [
    {
      "id": "400107",
      "postDate": "10/07/2018 15:56:12",
      "content": "<p>Are the flux values really some sort of flux difference from a \"baseline\" value that is different for each object?</p>",
      "rawMarkdown": "Are the flux values really some sort of flux difference from a \"baseline\" value that is different for each object?",
      "votes": null
    },
    {
      "id": "400794",
      "postDate": "10/08/2018 22:34:45",
      "content": "<p>Hi Iain,</p>\n\n<p>Correct - this \"difference imaging\" and the meaning of the <code>flux</code> column is described in the data note (<a href=\"https://arxiv.org/pdf/1810.00001.pdf\">https://arxiv.org/pdf/1810.00001.pdf</a>, page 2--3) and the starter kit kernel (<a href=\"https://www.kaggle.com/michaelapers/the-plasticc-astronomy-starter-kit\">https://www.kaggle.com/michaelapers/the-plasticc-astronomy-starter-kit</a>, Sec. 2c). </p>\n\n<p>Best,</p>\n\n<p>-Gautham on behalf of the PLAsTiCC team</p>",
      "rawMarkdown": "Hi Iain,\n\nCorrect - this \"difference imaging\" and the meaning of the `flux` column is described in the data note (https://arxiv.org/pdf/1810.00001.pdf, page 2--3) and the starter kit kernel (https://www.kaggle.com/michaelapers/the-plasticc-astronomy-starter-kit, Sec. 2c). \n\nBest,\n\n-Gautham on behalf of the PLAsTiCC team",
      "votes": null
    },
    {
      "id": "412347",
      "postDate": "10/30/2018 03:28:18",
      "content": "<p>Thanks Gautham for the response. One extra question about the \"difference imaging\". How is it calculated? Reading some discussions, I understood that the procedure is to compare each image (i1, i2, i3, ...iN) minus template (T), example:  i1-T = flux1, i2-T=flux2, ... iN-T=fluxN... Sincerely, I always believed that differences were calculated against the \"last image taken\" by the LSST, example:  (i1-Template = flux1, i2-i1 = flux2, ... iN-iN-1 = fluxN)... I think the second procedure is more \"real\" to evaluate the light changes... Is it some kind of LSST calculation/data access restriction? Thank you!</p>",
      "rawMarkdown": "Thanks Gautham for the response. One extra question about the \"difference imaging\". How is it calculated? Reading some discussions, I understood that the procedure is to compare each image (i1, i2, i3, ...iN) minus template (T), example:  i1-T = flux1, i2-T=flux2, ... iN-T=fluxN... Sincerely, I always believed that differences were calculated against the \"last image taken\" by the LSST, example:  (i1-Template = flux1, i2-i1 = flux2, ... iN-iN-1 = fluxN)... I think the second procedure is more \"real\" to evaluate the light changes... Is it some kind of LSST calculation/data access restriction? Thank you!",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 400794,
      "author_name": "gsnarayan",
      "author_url": "",
      "post_date": "10/08/2018 22:34:45",
      "content": "<p>Hi Iain,</p>\n\n<p>Correct - this \"difference imaging\" and the meaning of the <code>flux</code> column is described in the data note (<a href=\"https://arxiv.org/pdf/1810.00001.pdf\">https://arxiv.org/pdf/1810.00001.pdf</a>, page 2--3) and the starter kit kernel (<a href=\"https://www.kaggle.com/michaelapers/the-plasticc-astronomy-starter-kit\">https://www.kaggle.com/michaelapers/the-plasticc-astronomy-starter-kit</a>, Sec. 2c). </p>\n\n<p>Best,</p>\n\n<p>-Gautham on behalf of the PLAsTiCC team</p>",
      "votes": null,
      "replies": []
    },
    {
      "id": 412347,
      "author_name": "jcfigueroa",
      "author_url": "",
      "post_date": "10/30/2018 03:28:18",
      "content": "<p>Thanks Gautham for the response. One extra question about the \"difference imaging\". How is it calculated? Reading some discussions, I understood that the procedure is to compare each image (i1, i2, i3, ...iN) minus template (T), example:  i1-T = flux1, i2-T=flux2, ... iN-T=fluxN... Sincerely, I always believed that differences were calculated against the \"last image taken\" by the LSST, example:  (i1-Template = flux1, i2-i1 = flux2, ... iN-iN-1 = fluxN)... I think the second procedure is more \"real\" to evaluate the light changes... Is it some kind of LSST calculation/data access restriction? Thank you!</p>",
      "votes": null,
      "replies": []
    }
  ],
  "raw_markdown_by_id": {
    "400107": "Are the flux values really some sort of flux difference from a \"baseline\" value that is different for each object?",
    "400794": "Hi Iain,\n\nCorrect - this \"difference imaging\" and the meaning of the `flux` column is described in the data note (https://arxiv.org/pdf/1810.00001.pdf, page 2--3) and the starter kit kernel (https://www.kaggle.com/michaelapers/the-plasticc-astronomy-starter-kit, Sec. 2c). \n\nBest,\n\n-Gautham on behalf of the PLAsTiCC team",
    "412347": "Thanks Gautham for the response. One extra question about the \"difference imaging\". How is it calculated? Reading some discussions, I understood that the procedure is to compare each image (i1, i2, i3, ...iN) minus template (T), example:  i1-T = flux1, i2-T=flux2, ... iN-T=fluxN... Sincerely, I always believed that differences were calculated against the \"last image taken\" by the LSST, example:  (i1-Template = flux1, i2-i1 = flux2, ... iN-iN-1 = fluxN)... I think the second procedure is more \"real\" to evaluate the light changes... Is it some kind of LSST calculation/data access restriction? Thank you!"
  },
  "source": "meta"
}