{
  "site": {
    "horizonProfile": {
      "observerElevM": 1372,
      "profile": {
        "N": 1.5,
        "NNE": 0.6,
        "NE": 3.2,
        "ENE": 4.7,
        "E": 5.2,
        "ESE": 5.3,
        "SE": 5.7,
        "SSE": 4.4,
        "S": 3.9,
        "SSW": 2.3,
        "SW": 2.9,
        "WSW": 7.5,
        "W": 8.3,
        "WNW": 11,
        "NW": 7.7,
        "NNW": 4.7
      },
      "south": {
        "worst": 5.7,
        "mean": 3.8,
        "dueSouth": 3.9
      },
      "core": {
        "coreAltitudeDeg": 12.3,
        "terrainDeg": 5.7,
        "marginDeg": 6.6,
        "verdict": "clear"
      },
      "computed": "2026-09-17",
      "parts": null
    },
    "id": "glacier",
    "name": "Glacier National Park",
    "region": "St. Mary, MT",
    "timezone": "America/Denver",
    "darkSkyPark": true,
    "kind": "area",
    "kindNote": "Every figure on this page is computed at the St. Mary Visitor Center, on the east side of the park, where the Park Service runs its summer astronomy programs from the Dusty Star Observatory. The park is big mountain country, so the sky and the horizon differ from valley to valley, and the terrain figure here is for that one point.",
    "insideNote": null,
    "mergedFrom": null,
    "visited": false,
    "bortle": null,
    "skyBrightness": null,
    "skyBrightnessFrom": null,
    "darknessNote": "Not measured. Nobody has published a sky-brightness reading for the visitor center that this site can point at. What the Park Service says is that light pollution's effects are evident even in Glacier's protected skies, that it monitors light pollution over the park in support of the certification, and that its own monitoring image shows lights from businesses half a mile outside the park and the visitor center's own light.",
    "lat": 48.7473,
    "lng": -113.439,
    "ground": null,
    "groundBy": null,
    "horizon": null,
    "access": null,
    "accessUnknown": [
      "Which spot to stand in: nowhere is pinned, because nobody from this site has been there. The visitor center is where the Park Service runs its programs, not a recommendation from anyone who has looked at the sky from it",
      "Where a car can stop after the visitor center closes, and whether it can stay the night",
      "Whether lights on the building or in the parking area stay on after the programs end",
      "Cell coverage at the visitor center",
      "What the parking area's own horizon looks like, as opposed to the computed terrain"
    ],
    "contact": {
      "mail": "PO Box 128, West Glacier, MT 59936",
      "phone": "406-888-7800"
    },
    "sources": [
      {
        "label": "NPS, Glacier National Park, Night Sky",
        "url": "https://www.nps.gov/glac/learn/nature/night-sky.htm"
      },
      {
        "label": "NPS, Glacier National Park, Astronomy Programs",
        "url": "https://www.nps.gov/glac/planyourvisit/astronomy-programs.htm"
      },
      {
        "label": "NPS, St. Mary Visitor Center",
        "url": "https://www.nps.gov/places/st-mary-visitor-center.htm"
      },
      {
        "label": "OpenStreetMap, Saint Mary Visitor Center (the coordinates)",
        "url": "https://www.openstreetmap.org/way/83326235"
      }
    ],
    "verified": "2026-09-17",
    "notes": "Glacier and Waterton Lakes across the border are certified together as an International Dark Sky Park, in the Park Service's own words. Its nightly astronomy programs are usually offered in July and August, again in its words, at St. Mary and at Apgar on the west side, with a 20-inch telescope at the Dusty Star Observatory at the St. Mary Visitor Center, and Logan Pass star parties happen on announced dates with tickets, because parking there is limited. That is the Park Service describing its own programs, not a visit by anyone from this site.",
    "lightSource": null
  },
  "days": 14,
  "generatedAt": "2026-09-18T04:10:44.053Z",
  "weather": {
    "source": "Open-Meteo",
    "error": null,
    "nightsCovered": 14,
    "nightsTotal": 14,
    "note": "Cloud forecast covers every night shown"
  },
  "headline": "The best night in the next 14 is Thursday September 17. Moon down after 10:33pm, clear skies.",
  "best": {
    "site": "glacier",
    "siteName": "Glacier National Park",
    "region": "St. Mary, MT",
    "date": "2026-09-17",
    "score": 93,
    "verdict": "Excellent",
    "headline": "Excellent night. Moon down after 10:33pm, clear skies.",
    "headlineLead": "Excellent night",
    "headlineDetail": "moon down after 10:33pm, clear skies",
    "milkyWay": {
      "visible": false,
      "maxAltitudeDeg": 7.6,
      "hoursUseful": 0,
      "bestAt": "9:33pm",
      "note": "Milky Way core only reaches 7.6°, low enough that haze takes most of it"
    },
    "window": {
      "darkFrom": "9:33pm",
      "darkTo": "5:27am",
      "hours": 7.92,
      "bestFrom": "10:33pm",
      "bestTo": "5:27am"
    },
    "factors": [
      {
        "key": "cloud",
        "name": "Cloud",
        "score": 92,
        "weight": 38,
        "note": "8% cloud, essentially clear"
      },
      {
        "key": "moon",
        "name": "Moon",
        "score": 99,
        "weight": 31,
        "note": "first quarter at 45%, sets 10:33pm, dark after that"
      },
      {
        "key": "darkness",
        "name": "Darkness",
        "score": 88,
        "weight": 19,
        "note": "7h55m of astronomical darkness, 9:33pm–5:27am"
      },
      {
        "key": "transparency",
        "name": "Transparency",
        "score": 88,
        "weight": 12,
        "note": "Dewpoint spread 10.8°C, dry and steady air"
      }
    ],
    "weatherBacked": true,
    "confidence": "full",
    "dataSources": {
      "astronomy": "SunCalc (local computation)",
      "weather": "Open-Meteo"
    },
    "weekday": "Thursday",
    "isWeekend": false
  },
  "bestWeekend": {
    "site": "glacier",
    "siteName": "Glacier National Park",
    "region": "St. Mary, MT",
    "date": "2026-09-19",
    "score": 77,
    "verdict": "Good",
    "headline": "Good night. Moon down after 12:23am, clear skies.",
    "headlineLead": "Good night",
    "headlineDetail": "moon down after 12:23am, clear skies",
    "milkyWay": {
      "visible": false,
      "maxAltitudeDeg": 7.4,
      "hoursUseful": 0,
      "bestAt": "9:28pm",
      "note": "Milky Way core only reaches 7.4°, low enough that haze takes most of it"
    },
    "window": {
      "darkFrom": "9:28pm",
      "darkTo": "5:31am",
      "hours": 8.05,
      "bestFrom": "12:23am",
      "bestTo": "5:31am"
    },
    "factors": [
      {
        "key": "cloud",
        "name": "Cloud",
        "score": 76,
        "weight": 38,
        "note": "20% cloud cover, 16% of it high"
      },
      {
        "key": "moon",
        "name": "Moon",
        "score": 93,
        "weight": 31,
        "note": "first quarter at 64%, sets 12:23am, dark after that"
      },
      {
        "key": "darkness",
        "name": "Darkness",
        "score": 89,
        "weight": 19,
        "note": "8h03m of astronomical darkness, 9:28pm–5:31am"
      },
      {
        "key": "transparency",
        "name": "Transparency",
        "score": 22,
        "weight": 12,
        "note": "Dewpoint spread 4.2°C, some haze possible"
      }
    ],
    "weatherBacked": true,
    "confidence": "full",
    "dataSources": {
      "astronomy": "SunCalc (local computation)",
      "weather": "Open-Meteo"
    },
    "weekday": "Saturday",
    "isWeekend": true
  },
  "nights": [
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-17",
      "score": 93,
      "verdict": "Excellent",
      "headline": "Excellent night. Moon down after 10:33pm, clear skies.",
      "headlineLead": "Excellent night",
      "headlineDetail": "moon down after 10:33pm, clear skies",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 7.6,
        "hoursUseful": 0,
        "bestAt": "9:33pm",
        "note": "Milky Way core only reaches 7.6°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:33pm",
        "darkTo": "5:27am",
        "hours": 7.92,
        "bestFrom": "10:33pm",
        "bestTo": "5:27am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 92,
          "weight": 38,
          "note": "8% cloud, essentially clear"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 99,
          "weight": 31,
          "note": "first quarter at 45%, sets 10:33pm, dark after that"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 88,
          "weight": 19,
          "note": "7h55m of astronomical darkness, 9:33pm–5:27am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 88,
          "weight": 12,
          "note": "Dewpoint spread 10.8°C, dry and steady air"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Thursday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-18",
      "score": 55,
      "verdict": "Fair",
      "headline": "Workable. Moon down after 11:20pm, 93% cloud.",
      "headlineLead": "Workable",
      "headlineDetail": "moon down after 11:20pm, 93% cloud",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 7.5,
        "hoursUseful": 0,
        "bestAt": "9:30pm",
        "note": "Milky Way core only reaches 7.5°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:30pm",
        "darkTo": "5:29am",
        "hours": 7.98,
        "bestFrom": "11:20pm",
        "bestTo": "5:29am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 0,
          "weight": 38,
          "note": "93% cloud, mostly high cirrus, thin to the eye but ruinous for photography"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 98,
          "weight": 31,
          "note": "first quarter at 55%, sets 11:20pm, dark after that"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 89,
          "weight": 19,
          "note": "7h59m of astronomical darkness, 9:30pm–5:29am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 65,
          "weight": 12,
          "note": "Dewpoint spread 8.5°C, some haze possible"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Friday",
      "isWeekend": true
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-19",
      "score": 77,
      "verdict": "Good",
      "headline": "Good night. Moon down after 12:23am, clear skies.",
      "headlineLead": "Good night",
      "headlineDetail": "moon down after 12:23am, clear skies",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 7.4,
        "hoursUseful": 0,
        "bestAt": "9:28pm",
        "note": "Milky Way core only reaches 7.4°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:28pm",
        "darkTo": "5:31am",
        "hours": 8.05,
        "bestFrom": "12:23am",
        "bestTo": "5:31am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 76,
          "weight": 38,
          "note": "20% cloud cover, 16% of it high"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 93,
          "weight": 31,
          "note": "first quarter at 64%, sets 12:23am, dark after that"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 89,
          "weight": 19,
          "note": "8h03m of astronomical darkness, 9:28pm–5:31am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 22,
          "weight": 12,
          "note": "Dewpoint spread 4.2°C, some haze possible"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Saturday",
      "isWeekend": true
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-20",
      "score": 87,
      "verdict": "Excellent",
      "headline": "Excellent night. Moon down after 1:30am, clear skies.",
      "headlineLead": "Excellent night",
      "headlineDetail": "moon down after 1:30am, clear skies",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 7.3,
        "hoursUseful": 0,
        "bestAt": "9:25pm",
        "note": "Milky Way core only reaches 7.3°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:25pm",
        "darkTo": "5:33am",
        "hours": 8.12,
        "bestFrom": "1:30am",
        "bestTo": "5:33am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 100,
          "weight": 38,
          "note": "0% cloud, essentially clear"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 85,
          "weight": 31,
          "note": "waxing gibbous at 73%, sets 1:30am, dark after that"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 90,
          "weight": 19,
          "note": "8h07m of astronomical darkness, 9:25pm–5:33am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 47,
          "weight": 12,
          "note": "Dewpoint spread 6.7°C, some haze possible"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Sunday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-21",
      "score": 81,
      "verdict": "Good",
      "headline": "Good night. Moon down after 2:38am, clear skies.",
      "headlineLead": "Good night",
      "headlineDetail": "moon down after 2:38am, clear skies",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 7.2,
        "hoursUseful": 0,
        "bestAt": "9:23pm",
        "note": "Milky Way core only reaches 7.2°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:23pm",
        "darkTo": "5:34am",
        "hours": 8.19,
        "bestFrom": "2:38am",
        "bestTo": "5:34am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 92,
          "weight": 38,
          "note": "6% cloud, essentially clear"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 73,
          "weight": 31,
          "note": "waxing gibbous at 81%, sets 2:38am, dark after that"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 91,
          "weight": 19,
          "note": "8h11m of astronomical darkness, 9:23pm–5:34am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 56,
          "weight": 12,
          "note": "Dewpoint spread 7.6°C, some haze possible"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Monday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-22",
      "score": 58,
      "verdict": "Fair",
      "headline": "Workable. Moon down after 3:50am, 50% cloud.",
      "headlineLead": "Workable",
      "headlineDetail": "moon down after 3:50am, 50% cloud",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 7,
        "hoursUseful": 0,
        "bestAt": "9:20pm",
        "note": "Milky Way core only reaches 7°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:20pm",
        "darkTo": "5:36am",
        "hours": 8.26,
        "bestFrom": "3:50am",
        "bestTo": "5:36am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 37,
          "weight": 38,
          "note": "50% cloud, mostly high cirrus, thin to the eye but ruinous for photography"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 55,
          "weight": 31,
          "note": "waxing gibbous at 88%, sets 3:50am, dark after that"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 92,
          "weight": 19,
          "note": "8h15m of astronomical darkness, 9:20pm–5:36am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 84,
          "weight": 12,
          "note": "Dewpoint spread 10.4°C, dry and steady air"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Tuesday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-23",
      "score": 39,
      "verdict": "Poor",
      "headline": "Poor conditions. Moon down after 5:03am, 100% cloud.",
      "headlineLead": "Poor conditions",
      "headlineDetail": "moon down after 5:03am, 100% cloud",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 6.9,
        "hoursUseful": 0,
        "bestAt": "9:18pm",
        "note": "Milky Way core only reaches 6.9°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:18pm",
        "darkTo": "5:37am",
        "hours": 8.32,
        "bestFrom": "5:03am",
        "bestTo": "5:37am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 0,
          "weight": 38,
          "note": "100% cloud, mostly high cirrus, thin to the eye but ruinous for photography"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 30,
          "weight": 31,
          "note": "waxing gibbous at 94%, sets 5:03am, dark after that"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 92,
          "weight": 19,
          "note": "8h19m of astronomical darkness, 9:18pm–5:37am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 100,
          "weight": 12,
          "note": "Dewpoint spread 12.6°C, dry and steady air"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Wednesday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-24",
      "score": 31,
      "verdict": "Poor",
      "headline": "Poor conditions. Moon up all night, 94% cloud.",
      "headlineLead": "Poor conditions",
      "headlineDetail": "moon up all night, 94% cloud",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 6.8,
        "hoursUseful": 0,
        "bestAt": "9:16pm",
        "note": "Milky Way core only reaches 6.8°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:16pm",
        "darkTo": "5:39am",
        "hours": 8.39,
        "bestFrom": "9:16pm",
        "bestTo": "5:39am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 0,
          "weight": 38,
          "note": "94% cloud, mostly high cirrus, thin to the eye but ruinous for photography"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 3,
          "weight": 31,
          "note": "full moon at 98%, up the whole window, washing out faint targets"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 93,
          "weight": 19,
          "note": "8h23m of astronomical darkness, 9:16pm–5:39am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 100,
          "weight": 12,
          "note": "Dewpoint spread 16.4°C, dry and steady air"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Thursday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-25",
      "score": 61,
      "verdict": "Fair",
      "headline": "Workable. Moon up all night, clear skies.",
      "headlineLead": "Workable",
      "headlineDetail": "moon up all night, clear skies",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 6.7,
        "hoursUseful": 0,
        "bestAt": "9:13pm",
        "note": "Milky Way core only reaches 6.7°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:13pm",
        "darkTo": "5:41am",
        "hours": 8.46,
        "bestFrom": "9:13pm",
        "bestTo": "5:41am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 92,
          "weight": 38,
          "note": "7% cloud, essentially clear"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 0,
          "weight": 31,
          "note": "full moon at 100%, up the whole window, washing out faint targets"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 94,
          "weight": 19,
          "note": "8h27m of astronomical darkness, 9:13pm–5:41am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 73,
          "weight": 12,
          "note": "Dewpoint spread 9.3°C, some haze possible"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Friday",
      "isWeekend": true
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-26",
      "score": 52,
      "verdict": "Fair",
      "headline": "Workable. Moon up all night, 26% cloud.",
      "headlineLead": "Workable",
      "headlineDetail": "moon up all night, 26% cloud",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 6.5,
        "hoursUseful": 0,
        "bestAt": "9:11pm",
        "note": "Milky Way core only reaches 6.5°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:11pm",
        "darkTo": "5:42am",
        "hours": 8.52,
        "bestFrom": "9:11pm",
        "bestTo": "5:42am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 67,
          "weight": 38,
          "note": "26% cloud, mostly high cirrus, thin to the eye but ruinous for photography"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 0,
          "weight": 31,
          "note": "full moon at 100%, up the whole window, washing out faint targets"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 95,
          "weight": 19,
          "note": "8h31m of astronomical darkness, 9:11pm–5:42am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 74,
          "weight": 12,
          "note": "Dewpoint spread 9.4°C, some haze possible"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Saturday",
      "isWeekend": true
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-27",
      "score": 46,
      "verdict": "Poor",
      "headline": "Poor conditions. Moon up all night, 37% cloud.",
      "headlineLead": "Poor conditions",
      "headlineDetail": "moon up all night, 37% cloud",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 6.4,
        "hoursUseful": 0,
        "bestAt": "9:09pm",
        "note": "Milky Way core only reaches 6.4°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:09pm",
        "darkTo": "5:44am",
        "hours": 8.59,
        "bestFrom": "9:09pm",
        "bestTo": "5:44am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 55,
          "weight": 38,
          "note": "37% cloud, mostly high cirrus, thin to the eye but ruinous for photography"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 0,
          "weight": 31,
          "note": "full moon at 97%, up the whole window, washing out faint targets"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 95,
          "weight": 19,
          "note": "8h35m of astronomical darkness, 9:09pm–5:44am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 60,
          "weight": 12,
          "note": "Dewpoint spread 8.0°C, some haze possible"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Sunday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-28",
      "score": 67,
      "verdict": "Fair",
      "headline": "Workable. Moon up all night, clear skies.",
      "headlineLead": "Workable",
      "headlineDetail": "moon up all night, clear skies",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 6.3,
        "hoursUseful": 0,
        "bestAt": "9:06pm",
        "note": "Milky Way core only reaches 6.3°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:06pm",
        "darkTo": "5:45am",
        "hours": 8.65,
        "bestFrom": "9:06pm",
        "bestTo": "5:45am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 96,
          "weight": 38,
          "note": "3% cloud, essentially clear"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 0,
          "weight": 31,
          "note": "waning gibbous at 92%, up the whole window, washing out faint targets"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 96,
          "weight": 19,
          "note": "8h39m of astronomical darkness, 9:06pm–5:45am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 100,
          "weight": 12,
          "note": "Dewpoint spread 13.3°C, dry and steady air"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Monday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-29",
      "score": 31,
      "verdict": "Poor",
      "headline": "Poor conditions. Moon up all night, 96% cloud.",
      "headlineLead": "Poor conditions",
      "headlineDetail": "moon up all night, 96% cloud",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 6.1,
        "hoursUseful": 0,
        "bestAt": "9:04pm",
        "note": "Milky Way core only reaches 6.1°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:04pm",
        "darkTo": "5:47am",
        "hours": 8.72,
        "bestFrom": "9:04pm",
        "bestTo": "5:47am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 0,
          "weight": 38,
          "note": "96% cloud, mostly high cirrus, thin to the eye but ruinous for photography"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 0,
          "weight": 31,
          "note": "waning gibbous at 85%, up the whole window, washing out faint targets"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 97,
          "weight": 19,
          "note": "8h43m of astronomical darkness, 9:04pm–5:47am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 100,
          "weight": 12,
          "note": "Dewpoint spread 13.3°C, dry and steady air"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Tuesday",
      "isWeekend": false
    },
    {
      "site": "glacier",
      "siteName": "Glacier National Park",
      "region": "St. Mary, MT",
      "date": "2026-09-30",
      "score": 26,
      "verdict": "Not worth the drive",
      "headline": "Not worth the drive. Moon up all night, 99% cloud.",
      "headlineLead": "Not worth the drive",
      "headlineDetail": "moon up all night, 99% cloud",
      "milkyWay": {
        "visible": false,
        "maxAltitudeDeg": 6,
        "hoursUseful": 0,
        "bestAt": "9:02pm",
        "note": "Milky Way core only reaches 6°, low enough that haze takes most of it"
      },
      "window": {
        "darkFrom": "9:02pm",
        "darkTo": "5:49am",
        "hours": 8.78,
        "bestFrom": "9:02pm",
        "bestTo": "5:49am"
      },
      "factors": [
        {
          "key": "cloud",
          "name": "Cloud",
          "score": 0,
          "weight": 38,
          "note": "99% cloud, mostly high cirrus, thin to the eye but ruinous for photography"
        },
        {
          "key": "moon",
          "name": "Moon",
          "score": 1,
          "weight": 31,
          "note": "waning gibbous at 76%, up the whole window, washing out faint targets"
        },
        {
          "key": "darkness",
          "name": "Darkness",
          "score": 98,
          "weight": 19,
          "note": "8h47m of astronomical darkness, 9:02pm–5:49am"
        },
        {
          "key": "transparency",
          "name": "Transparency",
          "score": 63,
          "weight": 12,
          "note": "Dewpoint spread 8.3°C, some haze possible"
        }
      ],
      "weatherBacked": true,
      "confidence": "full",
      "dataSources": {
        "astronomy": "SunCalc (local computation)",
        "weather": "Open-Meteo"
      },
      "weekday": "Wednesday",
      "isWeekend": false
    }
  ]
}