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ISS SHADOWTRACE

Author: Alan Catovic · v1.0

ISS ShadowTrace is a browser-based precision tool for predicting and planning transits of the International Space Station (ISS) across the Sun and Moon. No installation required — everything runs locally in your browser.

Core Calculations

Solar transits & close passes — precise detection using center-line ray-casting (ISS→Sun direction intersected with WGS84 ellipsoid)
Lunar transits & close passes — same methodology as transit-finder.com; angular-separation minimization for accurate center-time
Topocentric Moon parallax (Meeus Ch.40) — corrects up to 57 arcminutes of geocentric error
Atmospheric refraction (Bennett formula) — lifts Sun/Moon apparent position by up to 20' at low elevations
Physical ISS size — 67 m effective angular radius for realistic transit width and path calculation
Sub-second timing precision — 45-iteration binary search for ingress/egress times
TLE propagation via satellite.js (SGP4/SDP4) with TLE age warnings and staleness alerts

Results & Display

UTC and local time side-by-side for every event
ISS angular diameter, slant range, azimuth, elevation, angular speed (arcsec/s)
Angular separation from Sun/Moon disk center
Center-line ground distance and visibility path width
Transit duration (ingress to egress) in seconds
Sky thumbnail showing ISS track relative to Sun/Moon disk
Moon phase rendered per event
Elevation profile chart ±5 minutes around transit
Weather forecast badge (cloud cover %) via Open-Meteo API
Confidence rating (High / Medium / Low) based on TLE age and geometry

Map & Planning

Interactive Leaflet map with transit corridors, center-lines and path width bands
Observer marker with 200 km reference circle
Solar (red) and lunar (blue) corridor color coding
Countdown timer to next upcoming event
Stellarium Web integration — opens sky view at exact event time
Astrophotography calculator: FOV, plate scale (arcsec/px), max exposure time
Real-time ISS tracker embedded (isstracker.pl widget)

Export & Sharing

Single-event or all-events .ics calendar export
CSV export with full orbital and geometric parameters
Shareable URL — encodes all search settings in a URL hash
Auto-loads settings from URL hash on page open
GPS location detection with automatic elevation lookup (Open-Meteo)

Note on accuracy: Results match transit-finder.com within 1–3 km (center-line) and 2–5 seconds (center-time) when using a fresh TLE (<12 h old). Lunar events with a TLE older than 24 h may diverge by 50–100 km due to ISS orbital drift. Always fetch a fresh TLE before planning an observation.

ISS ShadowTrace je precizni alat koji radi u browseru i služi za predviđanje i planiranje tranzita Međunarodne svemirske stanice (ISS) ispred Sunca i Mjeseca. Nije potrebna instalacija — sve se izvršava lokalno u vašem browseru.

Osnovni proračuni

Solarni tranziti i bliski prolazi — precizna detekcija pomoću center-line ray-castinga (smjer ISS→Sunce, presjek s WGS84 elipsoidom)
Lunarni tranziti i bliski prolazi — isti metodologija kao transit-finder.com; minimizacija kutnog rastojanja za tačno centralno vrijeme
Topocentrička paralaksa Mjeseca (Meeus Ch.40) — korigira do 57 lučnih minuta geocentrične greške
Atmosferska refrakcija (Bennettova formula) — podiže prividnu poziciju Sunca/Mjeseca do 20' pri niskim elevacijama
Fizičke dimenzije ISS-a — efektivni kutni polumjer 67 m za realan proračun širine tranzitnog koridora
Preciznost ispod sekunde — binarna pretraga s 45 iteracija za ingress/egress vremena
TLE propagacija putem satellite.js (SGP4/SDP4) s upozorenjima o starosti TLE-a

Rezultati i prikaz

UTC i lokalno vrijeme prikazani jedan pored drugog za svaki događaj
Kutni prečnik ISS-a, kosa udaljenost, azimut, elevacija, kutna brzina (arcsec/s)
Kutno rastojanje od centra diska Sunca/Mjeseca
Udaljenost centar-linije i širina puta vidljivosti na tlu
Trajanje tranzita (od ingressa do egressа) u sekundama
Minijaturni prikaz neba — položaj ISS-a u odnosu na disk Sunca/Mjeseca
Prikaz faze Mjeseca za svaki događaj
Graf elevacijske putanje ±5 minuta oko tranzita
Prognoza oblačnosti (%) putem Open-Meteo API-ja
Ocjena pouzdanosti (Visoka / Srednja / Niska) na osnovu starosti TLE-a i geometrije

Mapa i planiranje

Interaktivna Leaflet mapa s koridorima tranzita, centralnim linijama i trakama puta
Marker posmatrača s referentnim krugom od 200 km
Crvena boja za solarne, plava za lunarne koridore
Odbrojavanje do sljedećeg predstojećeg događaja
Integracija sa Stellarium Web — otvara prikaz neba u tačno vrijeme događaja
Astrofotografski kalkulator: FOV, plate scale (arcsec/px), maksimalni exposure
Ugrađeni ISS tracker u realnom vremenu (widget isstracker.pl)

Export i dijeljenje

Export u .ics kalendar — jedan događaj ili svi odjednom
CSV export sa svim orbitalnim i geometrijskim parametrima
Dijeljivi URL — enkodira sve parametre pretrage u URL hash
Automatsko učitavanje postavki iz URL hash-a pri otvaranju stranice
Automatska detekcija GPS lokacije s dohvatom nadmorske visine (Open-Meteo)

Napomena o tačnosti: Rezultati se poklapaju s transit-finder.com unutar 1–3 km (center-line) i 2–5 sekundi (centralno vrijeme) uz svježi TLE (<12 h). Lunarni događaji s TLE-om starijim od 24 h mogu odstupati 50–100 km zbog drifta ISS orbite. Uvijek dohvati svježi TLE prije planiranja posmatranja.

ISS SHADOWTRACE

Solar & Lunar transits of the International Space Station

Author: Alan Catovic

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Run a search to see next event countdown

Observer Location

Latitude (°N)

Longitude (°E)

Altitude (m)

TLE Data

Search Parameters

Start (UTC)

Duration (days)

Profile

Target

Min ISS Elevation (°)

Max center-line dist. (km)

📷 Astrophotography Calculator

Focal length (mm)

Sensor width (mm)

Sensor height (mm)

Pixel pitch (µm)

FOV: –

Plate scale: –

ISS speed (500 km): –

Max exposure: –

Max exposure = max shutter speed before ISS blurs across 1 pixel.

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