{
  "dataset": {
    "title": "Astrocartography Orbs: How Close Counts, With Sources",
    "canonical": "https://astrocartographers.com/accuracy/orb-thresholds",
    "data": "https://astrocartographers.com/accuracy/orb-thresholds/data",
    "published": "2026-08-01",
    "publisher": "Astrocartographers",
    "license": "https://creativecommons.org/licenses/by/4.0/",
    "licenseLabel": "CC BY 4.0",
    "note": "Every published astrocartography orb figure with its source, the mile-to-kilometre conversion rule, the four bands this engine uses, and the relocated-angularity degree bands. One band is deliberately uncited and is labelled as ours.",
    "citation": "Astrocartographers, \"Astrocartography Orbs: How Close Counts, With Sources\", https://astrocartographers.com/accuracy/orb-thresholds, published 2026-08-01."
  },
  "kmPerMile": 1.609344,
  "rounding": {
    "sourceKm": "miles * kmPerMile, rounded to the nearest km",
    "bandKm": "miles * kmPerMile, rounded to the nearest 5 km"
  },
  "grades": [
    {
      "grade": "A",
      "means": "Jim Lewis's own published words, the field's originator."
    },
    {
      "grade": "B",
      "means": "A named practitioner in print, under their own byline."
    },
    {
      "grade": "C",
      "means": "A vendor's encyclopedia, no individual author."
    }
  ],
  "sources": [
    {
      "grade": "A",
      "author": "Jim Lewis",
      "work": "Cyclo*Carto*Graphy handbook, 1982, pp. 6–7 (via Currey)",
      "quote": "up to 700 miles each side of where they pass",
      "miles": 700,
      "outerMiles": 700
    },
    {
      "grade": "A",
      "author": "Jim Lewis",
      "work": "Professional Training seminar, 1993, p. 26 (via Siregar)",
      "quote": "700-800 miles either side of the line; that's a huge orb",
      "miles": [
        700,
        800
      ],
      "outerMiles": 800
    },
    {
      "grade": "B",
      "author": "Moses Siregar III",
      "work": "The only source grading the whole range rather than quoting one outer limit",
      "quote": "under 150 miles very close; 200-350 miles moderate; 350-500 miles weak though still important; I use something like 500 miles as the outer range",
      "miles": 500,
      "outerMiles": 500
    },
    {
      "grade": "B",
      "author": "Ken Irving",
      "work": "Lewis's posthumous co-author (via Currey)",
      "quote": "standard around 300 miles, with a maximum orb of 700 miles in some cases",
      "miles": [
        300,
        700
      ],
      "outerMiles": 700
    },
    {
      "grade": "B",
      "author": "Robert Currey",
      "work": "Certified A*C*G Consultant",
      "quote": "within 350 miles … predominant; 700 miles weak, but hard to discern",
      "miles": 350,
      "outerMiles": 700,
      "url": "https://astrocartography.uk/acgorbs.htm"
    },
    {
      "grade": "B",
      "author": "Dale O'Brien & Martin Davis",
      "work": "in Davis (ed.), From Here to There",
      "quote": "a range of relevance up to 500 miles in either direction",
      "miles": 500,
      "outerMiles": 500
    },
    {
      "grade": "C",
      "author": "Astrodienst AstroWiki",
      "work": "Vendor encyclopedia, no byline",
      "quote": "around 1000 km either side of this line, although the influence wanes",
      "miles": 621,
      "outerMiles": 621
    }
  ],
  "bands": [
    {
      "label": "Under the line",
      "km": 80,
      "miles": null,
      "attribution": "Ours. No source at this radius, and we say so.",
      "means": "Close enough that the line is the first thing worth saying about the place. This is the only band with no citation behind it, and it is deliberately stricter than every source's innermost figure: Siregar's very close begins at 150 miles, Martin Davis's tight working practice at 150. A band this strict can only ever under-claim, and it is the only band allowed to say under the line, so that is the right direction to err in."
    },
    {
      "label": "Peak",
      "km": 320,
      "miles": 200,
      "attribution": "Siregar: the top of his strong band, where moderate begins.",
      "means": "The line is doing real work here. Most of what a reading says about a place is said from inside this band."
    },
    {
      "label": "Background",
      "km": 565,
      "miles": 350,
      "attribution": "Siregar's moderate/weak boundary, and the same 350 miles Currey calls predominant.",
      "means": "Present, and worth naming once, but not the thing that decides how a place reads."
    },
    {
      "label": "Faint",
      "km": 805,
      "miles": 500,
      "attribution": "Siregar's outer range, and O'Brien & Davis's up to 500 miles in either direction.",
      "means": "The tightest outer limit anybody publishes. Past here a reading should say nothing, and ours says nothing."
    }
  ],
  "angularityBands": [
    {
      "label": "Strong",
      "deg": 3,
      "means": "The planet sits within this many degrees of the angle in a chart recast for the place."
    },
    {
      "label": "Moderate",
      "deg": 6,
      "means": "Present in the relocated chart, and worth naming beside the ground distance."
    },
    {
      "label": "Out",
      "deg": 8,
      "means": "Siregar's stated outer limit: eight degrees at most from any angle in the relocated chart."
    }
  ],
  "spread": {
    "tightestMiles": 500,
    "widestMiles": 800,
    "factor": 1.6,
    "tightestKm": 805,
    "widestKm": 1287
  },
  "lewisCaveat": "the lines are not nearly as strong if you're at the edge than if you're right under the line"
}