"visual magnitude" meaning in English

{
  "forms": [
    {
      "form": "visual magnitudes",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "visual magnitude (plural visual magnitudes)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Astronomy",
          "orig": "en:Astronomy",
          "parents": [
            "Sciences",
            "Space",
            "All topics",
            "Nature",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "The apparent magnitude of a star in the central part of the spectrum of visible light"
      ],
      "id": "en-visual_magnitude-en-noun-EZQCtoXV",
      "links": [
        [
          "astronomy",
          "astronomy"
        ],
        [
          "apparent magnitude",
          "apparent magnitude"
        ],
        [
          "star",
          "star"
        ],
        [
          "spectrum",
          "spectrum"
        ],
        [
          "visible light",
          "visible light"
        ]
      ],
      "raw_glosses": [
        "(astronomy) The apparent magnitude of a star in the central part of the spectrum of visible light"
      ],
      "topics": [
        "astronomy",
        "natural-sciences"
      ]
    }
  ],
  "word": "visual magnitude"
}

{
  "forms": [
    {
      "form": "visual magnitudes",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "visual magnitude (plural visual magnitudes)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Astronomy"
      ],
      "glosses": [
        "The apparent magnitude of a star in the central part of the spectrum of visible light"
      ],
      "links": [
        [
          "astronomy",
          "astronomy"
        ],
        [
          "apparent magnitude",
          "apparent magnitude"
        ],
        [
          "star",
          "star"
        ],
        [
          "spectrum",
          "spectrum"
        ],
        [
          "visible light",
          "visible light"
        ]
      ],
      "raw_glosses": [
        "(astronomy) The apparent magnitude of a star in the central part of the spectrum of visible light"
      ],
      "topics": [
        "astronomy",
        "natural-sciences"
      ]
    }
  ],
  "word": "visual magnitude"
}