{ "schema": 1, "retrieved_date": "2026-10-02", "purpose": "Independent educational sky simulation, not NPS endorsement or an observing forecast.", "location": { "name": "Sunset Point", "latitude": 37.622568, "longitude": -112.165988, "coordinate_reference": "NPS public POI object 7763, WGS84 longitude/latitude; rounded to 6 decimals", "coordinate_accuracy": "Unknown in NPS source", "height_assumption": "0 m on WGS84 ellipsoid for lunar parallax; not the actual site elevation", "source": "nps-location" }, "sources": [ { "id": "hyg", "title": "HYG Database 4.1", "short_title": "HYG catalogue", "publisher": "David Nash / Astronexus", "author": "David Nash", "url": "https://github.com/astronexus/HYG-Database/tree/c7f7f883fe678cc7680169a50ccd7dcc49b060ce/hyg", "date": "Version 4.1; repository pinned by commit", "rights": "CC BY-SA 4.0; runtime subset and catalogue-derived charts retain the same license and attribution.", "supports": [ "Star positions at epoch/equinox J2000.0", "Apparent visual magnitude", "Catalogue identities and names", "Maximum omitted proper motion in the subset" ], "local_evidence": "content/night-sky/research/catalog-acquisition.json", "limits": "Archived version deliberately pinned. Some companion names with B are unofficial per the README. Variable star brightness is not animated. The catalogue is not a list of guaranteed naked-eye detections." }, { "id": "nps-location", "title": "NPS Public Points of Interest — Sunset Point, object 7763", "short_title": "NPS location", "publisher": "National Park Service, National Geospatial Program", "author": "National Park Service", "url": "https://mapservices.nps.gov/arcgis/rest/services/NationalDatasets/NPS_Public_POIs/FeatureServer/0/7763?f=pjson", "date": "Live public record retrieved 2026-10-02; no source revision date asserted", "rights": "U.S. Government public data; source method NAIP, Harpers Ferry retained. No source imagery copied.", "supports": [ "Fixed published location: 37.622568244798885 N, -112.1659876923019 E" ], "local_evidence": "content/night-sky/research/nps-sunset-point.json", "limits": "Accuracy field is Unknown. The point is not a parking entrance, accessibility assessment, local skyline or access permission." }, { "id": "schlyter", "title": "How to compute planetary positions", "short_title": "Orbital formulas", "publisher": "Paul Schlyter", "author": "Paul Schlyter", "url": "https://stjarnhimlen.se/comp/ppcomp.html", "date": "Undated online reference; describes formulas developed in 1979 from van Flandern and Pulkkinen", "rights": "Mathematical methods used in an original implementation; article, diagrams and program code are not republished.", "supports": [ "Low-precision solar and lunar elements", "Lunar longitude, latitude and distance perturbations", "Coordinate transformations and topocentric distinction" ], "limits": "The article's accuracy claim is not adopted without testing. This lane uses wider teaching tolerances, a full ellipsoid observer-vector subtraction, and independent Horizons checks." }, { "id": "meeus", "title": "Astronomical Algorithms, second edition, chapters 12 and 21", "short_title": "Meeus, 1998", "publisher": "Willmann-Bell", "author": "Jean Meeus", "url": "https://ui.adsabs.harvard.edu/abs/1998asal.book.....M/abstract", "date": "1998", "rights": "Numerical formulas and facts implemented independently; no book text, tables or artwork republished.", "supports": [ "Mean sidereal time equation 12.4", "IAU 1976 J2000-to-date precession" ], "limits": "Bibliographic reference only: no book text was acquired, and ADS was inaccessible in this session. The independent numerical evidence is the ERFA/SOFA matrix and JPL Horizons, not an assertion that the full book was re-read. Mean coordinates omit nutation and aberration." }, { "id": "erfa", "title": "ERFA authoritative test vectors for IAU 1976 precession", "short_title": "ERFA reference", "publisher": "ERFA / NumFOCUS", "author": "ERFA and IAU SOFA contributors", "url": "https://github.com/liberfa/erfa/blob/master/src/t_erfa_c.c", "date": "Retrieved 2026-10-02; relevant numerical test values retained", "rights": "Numerical validation facts; no ERFA runtime dependency or source redistribution.", "supports": [ "Independent pmat76 matrix case" ], "limits": "Numerical reference check is not professional astronomer review." }, { "id": "jpl-horizons", "title": "Horizons System — observer tables and documented quantities", "short_title": "NASA/JPL Horizons", "publisher": "NASA Jet Propulsion Laboratory, Solar System Dynamics", "author": "JPL Solar System Dynamics Group", "url": "https://ssd.jpl.nasa.gov/horizons/manual.html", "date": "Reference queries 2026-10-02; DE441 ephemeris", "rights": "Public NASA/JPL numerical output retained for verification with provenance; no imagery used.", "supports": [ "Independent Sun and Moon azimuth/altitude", "Independent lunar illuminated fraction", "Apparent sidereal time comparison", "Airless topocentric reference conventions" ], "local_evidence": "content/night-sky/research/jpl-sun.json and jpl-moon.json, with exact query receipts", "limits": "Reference rows are samples, not exhaustive error proof. Future Earth orientation is predicted/extrapolated. JPL's topocentric phase is compared with the model's geocentric phase using a 2-percentage-point allowance." }, { "id": "esa-galactic", "title": "Gaia DR3 documentation §4.1.7 — Galactic coordinates", "short_title": "ESA coordinate frame", "publisher": "European Space Agency / Gaia DPAC", "author": "Alexey Butkevich and Lennart Lindegren", "url": "https://gea.esac.esa.int/archive/documentation/GDR3/Data_processing/chap_cu3ast/sec_cu3ast_intro/ssec_cu3ast_intro_tansforms.html", "date": "Gaia DR3 documentation release 1.3", "rights": "Coordinate transformation facts; no ESA image or diagram reproduced.", "supports": [ "ICRS-to-Galactic rotation defining the Galactic equator" ], "limits": "The band width and glow in the classroom are original schematic styling, not measured Milky Way brightness or dust structure." }, { "id": "nps-sky", "title": "Night Skies — Bryce Canyon National Park", "short_title": "NPS night skies", "publisher": "National Park Service", "author": "Bryce Canyon National Park", "url": "https://www.nps.gov/brca/learn/nature/night-skies.htm", "date": "Updated 2026-07-11", "rights": "Paraphrased interpretive facts; no photographs copied or photo rights inferred.", "supports": [ "Bryce dark-sky educational context", "Milky Way under clear, dark, new-Moon conditions", "Light stewardship" ], "limits": "The page's blanket two-hours-after-sunset statement and older Andromeda distance are not used. This product does not infer current conditions or program availability." }, { "id": "nps-stargazing", "title": "Stargazing at Bryce Canyon", "short_title": "NPS stargazing", "publisher": "National Park Service", "author": "Bryce Canyon National Park", "url": "https://www.nps.gov/thingstodo/stargazing-at-bryce-canyon.htm", "date": "Updated 2024-10-10", "rights": "Paraphrased facts and outbound reading link only; no media reused.", "supports": [ "Use official calendar or visitor center for actual programs", "Sunset Point is among the interpretive stargazing locations" ], "limits": "No present accessibility or weather guarantee is imported. No route, hike or new program schedule is recommended." }, { "id": "nasa-polaris", "title": "What Is the North Star and How Do You Find It?", "short_title": "NASA: Polaris", "publisher": "NASA / JPL-Caltech", "author": "Preston Dyches", "url": "https://science.nasa.gov/solar-system/skywatching/what-is-the-north-star-and-how-do-you-find-it/", "date": "Published 2021-07-28; updated 2024-11-06", "rights": "Paraphrased astronomical interpretation; no images reused.", "supports": [ "Polaris near the north celestial pole", "Daily apparent stellar rotation", "True north versus magnetic north", "Big Dipper finding aid" ], "limits": "The latitude/altitude relationship is a spherical-geometry consequence; exact Polaris altitude is calculated, not set equal to latitude." }, { "id": "nasa-asterisms", "title": "What Are Asterisms?", "short_title": "NASA: asterisms", "publisher": "NASA / JPL-Caltech", "author": "NASA Skywatching", "url": "https://science.nasa.gov/solar-system/what-are-asterisms/", "date": "Updated 2024-11-06", "rights": "Short factual paraphrases; original line drawings use HYG positions, not copied chart artwork.", "supports": [ "Summer Triangle members", "Winter Triangle members", "Asterisms are recognizable patterns" ], "limits": "Line choices are teaching aids, not official boundaries or physical links between stars." }, { "id": "nasa-arcturus", "title": "What's Up: September 2021", "short_title": "NASA: finding Arcturus", "publisher": "NASA / JPL-Caltech", "author": "NASA Skywatching", "url": "https://science.nasa.gov/resource/whats-up-september-2021/", "date": "2021-09", "rights": "Paraphrased finding technique; no media or old event predictions reused.", "supports": [ "Following the Big Dipper handle's arc to Arcturus" ], "limits": "The May example time and positions are newly calculated teaching choices, not quoted from an old monthly sky forecast." }, { "id": "nasa-seasons", "title": "What Are Constellations?", "short_title": "NASA: changing seasons", "publisher": "NASA Space Place", "author": "NASA / JPL-Caltech", "url": "https://spaceplace.nasa.gov/constellations/en/", "date": "Undated page retrieved 2026-10-02", "rights": "Paraphrased educational facts; no images reused.", "supports": [ "Different evening constellations as Earth orbits the Sun" ], "limits": "Seasonal scenes are examples, not exclusive visibility windows." }, { "id": "nasa-milky-way", "title": "Skywatching — galaxies and the Milky Way", "short_title": "NASA: our galaxy", "publisher": "NASA", "author": "NASA Skywatching", "url": "https://science.nasa.gov/skywatching/", "date": "Page retrieved 2026-10-02", "rights": "Paraphrased explanation only. Third-party photographs on this page are not reused.", "supports": [ "Milky Way band as our view through the disk from within it" ], "limits": "No visual observation or exact apparent band width at Bryce is asserted." }, { "id": "nasa-cassiopeia", "title": "IC 63 Ghost Nebula", "short_title": "NASA: Cassiopeia", "publisher": "NASA, ESA and STScI", "author": "Hubble science team", "url": "https://science.nasa.gov/asset/hubble/ic-63-ghost-nebula/", "date": "2018", "rights": "Paraphrased context about Cassiopeia only; the nebula image is not used.", "supports": [ "Cassiopeia W high on autumn and winter evenings at mid-northern latitudes" ], "limits": "No claim that the faint nebula is visible unaided; it is not included in the chart." }, { "id": "nasa-moon", "title": "Moon Phases", "short_title": "NASA: lunar phases", "publisher": "NASA", "author": "NASA lunar science education", "url": "https://science.nasa.gov/moon/moon-phases/", "date": "Page retrieved 2026-10-02", "rights": "Paraphrased explanation; no diagrams or photographs reused.", "supports": [ "Reflected sunlight", "Lunar phase geometry", "Phase and time above the horizon differ" ], "limits": "No copied current-phase widget or prediction feed. Full/new labels are approximate neighborhoods, not event times." }, { "id": "noaa-twilight", "title": "Definitions of Twilight", "short_title": "NOAA: twilight", "publisher": "NOAA National Weather Service", "author": "National Weather Service, Sioux Falls", "url": "https://www.weather.gov/fsd/twilight", "date": "Undated page retrieved 2026-10-02", "rights": "Paraphrased geometric definitions; no media reused.", "supports": [ "Civil, nautical and astronomical twilight boundaries at solar center altitudes -6, -12 and -18 degrees" ], "limits": "This tool calls center altitude >=0 daylight. Actual sunrise/sunset includes limb/refraction and is not calculated." }, { "id": "nps-adaptation", "title": "Stargazing — Zion National Park", "short_title": "NPS: dark adaptation", "publisher": "National Park Service", "author": "Zion National Park", "url": "https://www.nps.gov/zion/planyourvisit/sunset-stargazing.htm", "date": "Page retrieved 2026-10-02", "rights": "Paraphrased general observing advice, not Zion-specific access information; no media copied.", "supports": [ "Roughly 20–30 minutes for dark adaptation after white light", "Restrained red lighting" ], "limits": "Display color does not guarantee preserved night vision. Device brightness and neighboring applications are outside this page's control." }, { "id": "nasa-faq", "title": "Skywatching FAQ", "short_title": "NASA skywatching FAQ", "publisher": "NASA", "author": "NASA Skywatching", "url": "https://science.nasa.gov/skywatching/faq/", "date": "Page retrieved 2026-10-02", "rights": "Paraphrased facts; no source artwork reused.", "supports": [ "Celestial directions and observing context", "Constellations versus asterisms", "Sirius as brightest night-sky star", "Landscape obstruction" ], "limits": "The chart is not a navigation or terrain-safety tool." }, { "id": "nasa-deneb", "title": "Summer Triangle Corner: Deneb", "short_title": "NASA: Deneb", "publisher": "NASA Night Sky Network", "author": "Kat Troche; original Night Sky Notes material", "url": "https://science.nasa.gov/solar-system/skywatching/night-sky-network/summer-triangle-corner-deneb/", "date": "Displayed 2026-08-15", "rights": "Short factual paraphrase; no Stellarium or other artwork reproduced.", "supports": [ "Deneb belongs to Cygnus and the Summer Triangle" ], "limits": "Distances and physical luminosities are deliberately omitted." }, { "id": "nasa-altair", "title": "Summer Triangle Corner: Altair", "short_title": "NASA: Altair", "publisher": "NASA Night Sky Network", "author": "Kat Troche; original Dave Prosper article", "url": "https://science.nasa.gov/solar-system/skywatching/night-sky-network/summer-triangle-corner-altair/", "date": "Displayed 2026-07-15; article also notes original August 2020 and update July 2025", "rights": "Short factual paraphrase; no artwork reproduced.", "supports": [ "Altair belongs to Aquila and the Summer Triangle" ], "limits": "Source date discrepancy retained. No instantaneous observing report is inferred." } ], "conflicts_and_exclusions": [ "USNO solar and sidereal FAQ endpoints failed to load in this session. They are not cited as checked sources or used as numerical evidence. JPL Horizons provides independent references instead.", "NPS Night Skies includes historical and simplified statements; blanket post-sunset duration, Andromeda distance, air quality history, fines and programs are not imported.", "HYG is an archived, explicitly pinned catalogue, not a current variable-star brightness service.", "No measured landscape horizon or night-sky brightness is available; no observing reports are fabricated.", "No agency affiliation, NPS endorsement, field station, ownership, route or current access claim is added.", "Meeus is a bibliographic reference, not an acquired source text; the linked ADS record was unavailable. ERFA and JPL supply the retained numerical checks." ] }