ℹ️ About this app

What it is

A free, single web app that plans and explains the Friday-evening public stargazing sessions at the Science Centre Observatory. It has two faces: a detailed dashboard for volunteers and docents (tonight's targets, weather go/no-go, the telescopes, a printable session pack), and a friendly, multilingual Sky Guide for visitors.

Everything astronomical — the Moon, the planets, deep-sky target heights, the sky map, sunrise and twilight times, comets, satellite passes — is computed live on your own device. The only thing that needs the internet is the live weather forecast; once the page has loaded it works fully offline, which is why it keeps running in the dome with no signal.

Where the numbers come from

Every figure is traceable. The astronomy is computed on-device from published methods; the live environmental data comes from official Singapore and open sources.

• Positions of the Sun, Moon & planets — the method of Paul Schlyter (How to compute planetary positions).
• Jupiter & Saturn detail — Jean Meeus, Astronomical Algorithms (Galilean moons, ring tilt); Great Red Spot longitude tracked to the JUPOS drift trend.
• Deep-sky catalogue — AstroPixels Messier & Caldwell catalogues, Fred Espenak.
• Double & carbon stars — Washington Double Star catalog (WDS) and SIMBAD, compiled.
• Twenty-Eight Mansions — stars & asterisms — member stars and connecting lines from the Stellarium “Chinese” sky culture, joined to Hipparcos (ESA) J2000 star positions.
• Chinese ↔ Western star names — the traditional per-star names (宿-numeral, e.g. 心宿二 = Antares) paired with modern Western designations follow the Hong Kong Space Museum bilingual star-name list (via Wikipedia's List of Chinese star names), itself after Yi Shitong, Atlas Comparing Chinese and Western Star Maps (1981) and Chen Meidong, Star Charts in Ancient China (1996).
• Almanac “mansion of the day” — the traditional East-Asian koyomi 二十八宿: a continuous 28-day calendar cycle assigned to each date (distinct from the Moon's real position), computed on-device and cross-checked against the calc-site and koyominote almanacs and the National Astronomical Observatory of Japan koyomi documentation.
• Indian nakshatras — junction stars & pañchāṅga — the 27 nakshatras' junction stars (yogatārā) after the standard list (Sūrya Siddhānta / B. V. Raman), matched to Hipparcos J2000; deities, symbols, gaṇas and the nine planetary lords after classical Jyotiṣa (Parāśara tradition); sidereal longitudes, the Moon's nakshatra and the pañchāṅga (tithi, yoga, karaṇa) computed on-device using the Lahiri (Chitrapakṣa) ayanāṁśa.
• Malay / Nusantara star-pictures & buruj — the indigenous bintang (Bintang Pari, Belantik/Waluku, Biduk, Bintang Tujuh/Kartika, Kala Jengking) from folk-astronomy studies of the Malay Peninsula and the wider Nusantara (Malay, Javanese & Bugis traditions); the twelve buruj from the Arabic zodiac of the Malay taqwim. Names given in Rumi with the traditional Jawi script.
• Babylonian constellations & zodiac — the figures and Three Paths of MUL.APIN (standard edition of Hunger & Pingree) with their generally accepted modern star identifications, at Hipparcos J2000 positions; the 12 zodiac signs after the Babylonian originals. Path membership follows MUL.APIN's ±17° declination bands.
• Egyptian figures & decans — Sah (Orion), Sopdet (Sirius) and Meskhetiu (the Big Dipper) are securely identified; Taweret (Draco) and the northern group follow the tomb-ceiling diagrams (Senmut, Seti I, Dendera). The 36 decans are shown as the 10-day timekeeping ring anchored on Sopdet; individual decan star-IDs remain uncertain in the scholarship.
• Maya figures & the Venus calendar — Tzab = the Pleiades, the Turtle/Hearthstones = Orion, Xaman Ek' = Polaris are well established (codices, Popol Vuh, living Maya lore); the ecliptic "zodiac" animals of the Paris Codex are more debated. The Venus cycle (583.92-day synodic period, the 8-year pentagram) follows the Dresden Codex; Venus computed on-device.
• Inca / Andean dark-cloud constellations — after Gary Urton, At the Crossroads of the Earth and the Sky (1981) and Andean ethnography. The bright figures use Hipparcos J2000 star positions; the dark-cloud animals are drawn as shaded silhouettes at the approximate positions of the Milky Way's dark nebulae (exact outlines vary between sources). The Llama's eyes are α & β Centauri.
• Polynesian star lines — the Hawaiian wayfinding system of the Polynesian Voyaging Society (Nainoa Thompson): the four star lines and the 32-house star compass, at Hipparcos J2000 positions.
• Aboriginal Australian figures — a small, widely-shared selection from published research (e.g. Ray Norris & Duane Hamacher with Aboriginal knowledge-holders); the Emu is a dark constellation drawn as a shaded silhouette (its true extent is far larger).
• Greek constellations & myths — the classical figures of Ptolemy's Almagest with their standard myths (Aratus, Ovid), at Hipparcos J2000 positions — the basis of the modern 88 IAU constellations used throughout this app.
• Shared engine — all newer culture pages compute star positions from one shared module, sky-culture-core.js (local sidereal time & alt/az for SCOB), with cross-culture links resolved against the loaded data files.
• Comets — heliocentric orbital elements from the Minor Planet Center / aerith.net, solved on-device; magnitudes use each comet's published brightness law m = g + 5·log Δ + K·log r. The dedicated Comets tonight page lists which tracked comets are up, how bright and where to point.
• Satellites (ISS, Tiangong, Hubble) — CelesTrak two-line elements, propagated on your device with satellite.js (SGP4), bundled with the app so passes compute offline.
• Weather & rain radar — Open-Meteo and the Meteorological Service Singapore (weather.gov.sg).
• Seeing & transparency — 7Timer! astro (with a local wind/humidity estimate as an offline fallback); surfaced in the glance summary, the session run-sheet and the Jupiter/Saturn high-power detail.
• Haze / air quality — 24-hour PSI and 1-hour PM2.5 for all five regions from the National Environment Agency via data.gov.sg; the multi-night outlook (PM2.5, PM10, dust and aerosol optical depth) from Open-Meteo’s air-quality model. Health bands and advisories are NEA’s (haze.gov.sg); the conversion from a particle concentration into magnitudes of lost sky — aerosol extinction along the air path, plus the extra sky glow the smoke scatters back down — is our own estimate, documented in haze-core.js. Airmass after Kasten & Young (1989). The regional picture — where the fires are burning and which way the smoke is being carried — leads with Singapore's own haze satellite product from the Meteorological Service Singapore (a false-colour NOAA-20 scene with MSS's own hotspot-confidence markers, the imagery behind the national haze bulletins), alongside NASA Worldview / GIBS imagery (VIIRS true colour and 375 m active-fire detections, VIIRS aerosol optical depth, Himawari-9 visible, and the VIIRS day-night band — each layer chosen by measuring how much of the Singapore region it actually covers, not by name), with the smoke-transport wind at 850 hPa from Open-Meteo. The authoritative regional products are the ASEAN Specialised Meteorological Centre (operated by the Meteorological Service Singapore) and MSS’s haze page. See the Haze & the night sky page.
• Solar activity & sunspots — NOAA Space Weather Prediction Center (regions, 10.7 cm flux, X-ray flares); the live white-light Sun image is courtesy NASA / SDO (HMI).
• Meteor showers — peak dates and Zenithal Hourly Rates are standard almanac values (radiant height & "from SCOB" rating computed on-device); deeper data from the International Meteor Organization and the American Meteor Society.
• Lunar surface features (Tonight on the Moon) — feature positions from the IAU/USGS Gazetteer of Planetary Nomenclature; phase, terminator (selenographic colongitude) and libration from the lunar theory of J. Meeus & P. Schlyter, computed on-device.
• Sky-events calendar — Sea & Sky astronomy calendar (seasky.org), covering 2026–2028; eclipse paths cross-checked against NASA/GSFC. The list carries an on-screen reminder when it nears its end so it never quietly runs dry.
• Eclipses (the solar & lunar eclipses page) — dates, types, durations and paths are from NASA's Goddard Eclipse Web Site (Espenak & Meeus), cross-checked with timeanddate.com; the world map is schematic and the countdown is computed on-device.
• Light-pollution realism & limiting magnitude — the Bortle dark-sky scale sets a clear-night limit for Jurong, which the app then reduces live for the Moon (illuminated fraction × altitude) and the current haze (west 24-h PSI) to estimate tonight's faintest deep-sky reach. A rough observing estimate, not photometry.
• Extreme-object facts (nebulae, neutron stars, black holes) — NASA and the ESA / Event Horizon Telescope Collaboration.
• Solar-system structure (the Solar System section: live orrery, the planets and beyond Neptune) — the live top-down orrery and apparent-retrograde loops are computed on-device from the same planetary elements as the positions above (Schlyter); orbital distances, periods and eccentricities are standard values from NASA/JPL Solar System Dynamics. Asteroid-belt, Kuiper-belt, dwarf-planet, heliosphere and Oort-cloud figures are standard published estimates (the Oort cloud has never been directly observed). Voyager 1 & 2 distances are projected from NASA/JPL Voyager tracking. The unconfirmed “Planet Nine” hypothesis follows Batygin & Brown (2016), now being tested by the Vera C. Rubin Observatory.
• Seestar S30 specifications — the manufacturer, ZWO.
• Imaging & visual filters — the filter reference's emission-line wavelengths (Hα 656.3, OIII 500.7, SII 671.6, Hβ 486.1 nm) follow standard atomic-spectroscopy values (NIST Atomic Spectra Database); the narrowband, dual-band, LRGB, planetary and solar filter guidance is compiled from filter-maker specifications and common astrophotography practice.
• Eyepiece designs — the eyepiece types guide describes the standard optical designs (Huygens, Ramsden, Kellner, Plössl, Abbe orthoscopic, Erfle and Nagler-type ultra-wides) and the apparent-field / eye-relief / exit-pupil relationships from established amateur-optics references; the pros, cons and quoted figures are typical values compiled from eyepiece-maker specifications and common observing practice.
• QR codes (kiosk, object cards & poster) — generated on-device with qrcode.js (davidshimjs), bundled with the app (self-hosted) so it works offline.

Sky lore & cultural star-names

The constellation pages tell the traditional Greek myths and, for Singapore's own communities and the ancient civilisations that first mapped the sky, how the same stars were named and pictured in several other traditions — each with its own full explainer and live tonight page, grouped under Skies across cultures in the menu:

• Chinese — the classical system of the Twenty-Eight Lunar Mansions, the Four Symbols and the Three Enclosures (e.g. 北斗 the Northern Dipper, 參 the Three Stars, the Qixi Cowherd & Weaving Girl), on the Chinese Sky and Chinese Sky Tonight pages. Mansion meanings and determinative stars follow standard references and Sun Xiaochun & Jacob Kistemaker, The Chinese Sky During the Han (Brill, 1997).
• Indian — the nakshatra tradition: the 27 lunar mansions, their nine planetary lords, deities and symbols, and the 12 rāśi, on the Indian Sky and Indian Sky Tonight pages. Names in Sanskrit (Devanagari) with IAST transliteration; the tonight page gives the Moon's nakshatra and the day's pañchāṅga.
• Arabic — the 28 lunar mansions (manāzil al-qamar) the Moon crosses each month and the anwāʾ weather-almanac: the third great lunar-mansion system, and the source of the Arabic star names the world still uses (Aldebaran, Altair, Deneb, Betelgeuse), on the Arabic Sky and Arabic Sky Tonight pages — the tonight page gives the Moon's own manzil from its live ecliptic longitude. All three lunar-mansion systems (Chinese 宿, Indian nakshatra, Arabic manzil) are matched star-by-star on the Three Lunar-Mansion Systems page. Roster after Ibn Qutayba's Kitāb al-Anwāʾ and Kunitzsch & Smart, A Dictionary of Modern Star Names.
• Malay & Nusantara — the indigenous star-pictures used for sea-navigation and the rice calendar (Bintang Pari, Belantik/Waluku, Biduk, Bintang Tujuh, Kala Jengking) and the 12 buruj, on the Malay Sky and Malay Sky Tonight pages. Names in Rumi with the traditional Jawi script; the tonight page gives a star compass, the Sun's buruj and Venus (Bintang Timur / Kejora).
• Babylonian — the constellations of MUL.APIN (c. 1000 BCE) sorted into the Three Paths of Enlil, Anu and Ea, and the 12-sign zodiac Babylon invented, on the Babylonian Sky and Babylonian Sky Tonight pages. These figures are the ancestors of the Greek/Western constellations. Names in Sumerian/Akkadian transliteration.
• Ancient Egyptian — Sah (Orion/Osiris), Sopdet (Sirius/Isis), Meskhetiu (the Big Dipper) and Taweret (Draco), the Imperishable and Unwearying stars, and the 36 decans that gave us the 24-hour day, on the Egyptian Sky and Egyptian Sky Tonight pages.
• Maya — Tzab (the rattlesnake's rattle, the Pleiades), the Turtle & Three Hearthstones (Orion), the Scorpion, the Peccaries (Gemini) and Xaman Ek' (Polaris), with Chak Ek' (Venus) and the Maya calendars, on the Maya Sky and Maya Sky Tonight pages.
• Inca / Andean — the bright figures (Qullqa the Pleiades, Chakana the Southern Cross) and the famous dark-cloud constellations of the Milky Way (Mayu) — Yacana the Llama, Yutu, the Fox, the Toad and the Serpent — on the Inca Sky and Inca Sky Tonight pages.
• Polynesian — the four Hawaiian wayfinding star lines and the star compass, with Hōkūleʻa (Arcturus), Māui's fishhook (Scorpius) and the Southern Cross, on the Polynesian Sky and Polynesian Sky Tonight pages.
• Aboriginal Australian — the Emu in the Sky (a dark constellation), the Seven Sisters (Pleiades), the canoe of Orion and the Southern Cross, on the Aboriginal Sky and Aboriginal Sky Tonight pages — among the oldest sky-stories on Earth.
• Greek — the classical constellations and their myths (the source of the modern Western sky), grouped by legend, with the twelve zodiac signs, on the Greek Sky and Greek Sky Tonight pages.
• Across the cultures — two synthesis pages tie the strand together: The Three Lunar-Mansion Systems (Chinese 宿 / Indian nakshatra / Arabic manzil matched star by star) and The Sky Through the Ages (all eleven traditions on one timeline, with a live cross-culture star explorer).

These are living, shared traditions passed down in many forms — often oral and regional — and different cultures grouped the stars differently, so the names are not always the exact same figure the Greeks drew. We've done our best to represent them accurately and respectfully; if you spot something to correct or add, please let the observatory team know.

Explore & understand the sky

A few visitor explainers on why the sky looks the way it does from here — the view a place gets is decided by its latitude and its lights. Everything on these pages is computed live on your device from the same engine as the rest of the app:

• Why Singapore sees almost the whole sky — from 1.3°N both celestial poles sit on the horizon, so over a year we can reach almost the entire celestial sphere; a declination-band chart and a landmark-by-landmark comparison against the world's great observatories, on the Singapore sees it all page.
• Northern vs southern hemisphere skies — why a stargazer in London and one in Sydney never share a sky: the two celestial poles, circumpolar stars, the seasonal flip, Polaris versus the Southern Cross, and why Orion and the Moon look upside down down south — then how Singapore, on the equator, gets both halves. On the Two hemispheres, two skies page.
• Where did all the stars go? — what city light pollution really costs: two simulated panels of the same star field (a dark site versus Jurong), the key idea that light pollution raises the background rather than hiding the sky, and an honest target-by-target table, on the Light pollution page.
• Haze & the night sky — the live NEA reading for Jurong (24-hour PSI and the faster-moving 1-hour PM2.5), today’s trend, where the smoke sits across the island and a five-night outlook — plus the two separate things smoke does to a telescope: it dims the stars (three times as much near the horizon as overhead) and it brightens the sky by scattering Jurong’s streetlights back down. With the health bands and what each means for a public night on the deck, and — because a ground sensor only reports what has already arrived — a regional satellite view of the fires and the smoke pall, with the transport wind aloft naming which upwind region (Riau, southern Sumatra, Kalimantan) is actually feeding us and roughly how many hours away it is, on the Haze page.

The telescopes

The Science Centre Observatory's fleet: a 40 cm (16") Cassegrain and a 15 cm (6") apochromatic refractor in the main dome; an 11" and a 7" in the second dome; portable Celestron CPC (8"–11") and C6 SCTs on the deck; and a ZWO Seestar S30 smart telescope. Every observing verdict in the app is tuned to these instruments, this site, and the roughly 7:30–10 pm session window.