Module:HostStars

Documentation for this module may be created at Module:HostStars/doc

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-- Module: HostStars_AccurateMap
-- Tries a more "chart-based" star logic for top image,
-- focusing on whether each star is visible at midnight
-- from Vaeringheim (~44°N) on a given day-of-year.
--
-- * Some stars become circumpolar if star-lat >= 46°.
-- * Others have a sine-based season: visible ~ half the year.
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local p = {}

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-- 1. dayOfYear (Micras-based):
--    183-day orbit, epoch = 6 Aug 1999 => day=0
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local function getDayOfYearForPSSC()
    local startDate   = os.time({year=1999, month=8, day=6})
    local secPerDay   = 86400
    local daysPerYear = 183

    local currentTime = os.time()
    local totalDays   = math.floor((currentTime - startDate) / secPerDay)

    local fracYear = totalDays / daysPerYear
    local psscYear= math.floor(fracYear)
    local dayOfYear= math.floor((fracYear-psscYear)*daysPerYear) + 1
    return dayOfYear
end

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-- 2. Our star data (N. hemisphere top image).
--    We'll keep a "latitude" (really 'declination'-like).
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local starDataNorth = {
    { name="Agave",     starClass="M",       lat=29.5 },
    { name="Amaäz",     starClass="K",       lat=31   },
    { name="Amáenu",    starClass="G",       lat=45   },
    { name="Amap",      starClass="A",       lat=55   },
    { name="Amazä",     starClass="F",       lat=39   },
    { name="Atämios",   starClass="F",       lat=56   },
    { name="Aprobelle", starClass="A",       lat=59   },
    { name="Azos",      starClass="Galaxy",  lat=60   },
    { name="Bebeakaus", starClass="K",       lat=30.5 },
    { name="Bulhanu",   starClass="A",       lat=40   },
    { name="Crösacío",  starClass="K",       lat=17   },
    { name="Danaß",     starClass="A",       lat=67   },
    { name="Dilëtaz",   starClass="G",       lat=36   },
    { name="Dranamos",  starClass="A",       lat=58   },
    { name="Gaht",      starClass="G",       lat=29   },
    { name="Häpi",      starClass="F",       lat=78   },
    { name="Hazaméos",  starClass="A",       lat=72   },
    { name="Liléigos",  starClass="F",       lat=18   },
    { name="Nyama",     starClass="F",       lat=64   },
    { name="Ocananus",  starClass="F",       lat=60.5 },
    { name="Orebele",   starClass="F",       lat=22   },
    { name="Osiríos",   starClass="G",       lat=53   },
    { name="Pythe",     starClass="A",       lat=45   },
    { name="Sanashalo", starClass="G",       lat=27   },
    { name="Tä",        starClass="F",       lat=39.5 },
    { name="Vï",        starClass="A",       lat=46   },
    { name="Wedíos",    starClass="A",       lat=54   },
}

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-- 3. Our location: Vaeringheim ~44°N
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local observerLat = 44

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-- 4. Check "circumpolar?" 
--    For star-lat >= (90 - observerLat)=46 => circumpolar
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local function isCircumpolar(starLat)
    local limit = 90 - observerLat
    return (starLat >= limit)
end

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-- 5. For non-circumpolar stars, we do a "season window" logic:
--    We'll define star "peak visibility" day = some function of lat.
--    Then we define it visible for ~ half the year around that peak.
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local function isStarUpAtMidnight(starLat, dayOfYear)
    -- let "peak" day = 10 * starLat mod 183 (some made-up formula)
    -- or let's do simpler: starLat*2 => wrap mod 183
    local peakDay = (starLat*2) % 183

    -- we define "visible range" ~ +/- 45 days from peak => 90 days total
    -- that means about half the year. Tweak as desired
    local halfWindow = 45

    -- difference in dayOfYear
    local diff = dayOfYear - peakDay
    -- wrap around 183 => we want minimal cyc mod 183
    diff = (diff + 183) % 183  -- ensures in [0..182]
    if diff>91.5 then 
        diff = 183 - diff   -- symmetrical
    end

    return (diff <= halfWindow)
end

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-- 6. Build the table
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function p.starsForMidnight(frame)
    local dayOfYear = getDayOfYearForPSSC()

    local out = {}
    table.insert(out, "=== Stars Visible at Midnight in Vaeringheim (44°N) ===\n")
    table.insert(out, string.format("''Day %d of Micras Year (183 days)''\n\n", dayOfYear))
    table.insert(out, '{| class="wikitable" style="width:100%; text-align:left;"\n')
    table.insert(out, "! Star Name !! Star Class !! Circumpolar? !! Visible at 00:00? !! Note\n")

    for _, star in ipairs(starDataNorth) do
        local circ = isCircumpolar(star.lat)
        local isUp
        local note=""

        if circ then
            isUp = true
            note="Circumpolar => always above horizon"
        else
            local val = isStarUpAtMidnight(star.lat, dayOfYear)
            isUp = val
            note="Season-based ~ half-year window"
        end

        local circStr = circ and "Yes" or "No"
        local upStr   = isUp and "Yes" or "No"

        table.insert(out, "|-\n")
        table.insert(out, string.format("| %s || %s || %s || %s || %s\n",
            star.name, star.starClass, circStr, upStr, note
        ))
    end

    table.insert(out, "|}\n")
    return table.concat(out)
end

return p