Astronomy & Geo: Sun, Moon, Planets and Coordinates

Astronomy & Geo is a six-panel workbench for positions, times and places: Sun, Moon, Planets, Satellites, Time Scales and Coordinates. Five panels share one location bar, so one latitude and longitude drive rise and set, phases, planet rows, passes and sidereal time; Coordinates reads its own fields.

Updated 2026-10-01Reviewed by CalcX Editorial Team6 sources4 min read

How to use the panels

Set the observer.Latitude and longitude drive Sun, Moon, Planets, Satellites and the LST card; Time Scales takes its own datetime, and Coordinates reads typed numbers.
Choose the date or instant.Sun and Moon take a date; Planets a local date and time; Time Scales ticks every second until you inspect a timestamp.
Read the cards first.Sunrise, sunset, solar noon and day length sit above the Sun curve; phase name, illuminated percentage, age and distance beside the phase disc; above-horizon planet rows are highlighted.
Work the tables.Twilight at −6°, −12° and −18°; the year's equinoxes and solstices; the next four Moon quarters.
Satellites and coordinates.Paste a TLE or fetch one from CelesTrak by NORAD ID, read the passes, export a calendar file; Coordinates converts, measures and outlines.

Worked examples

Sky readouts use the default observer (Beijing, 39.9042° N, 116.4074° E) on a UTC+8 clock; geodesy readouts do not depend on the clock.

Panel	Fixed input	Readout
Sun	1 Oct 2026	Sunrise 06:10, sunset 17:57, solar noon 12:04 · 46.9°, day length 11h 47m
Sun · twilight	1 Oct 2026	Civil 05:43 / 18:24, nautical 05:11 / 18:55, astronomical 04:40 / 19:27
Moon	1 Oct 2026, 12:00	Waning Gibbous, illuminated 76.3%, age 20.0 days, 369,485 km, magnitude −11.2; full moon Oct 26 12:12
Planets	1 Oct 2026, 12:00	Jupiter altitude 44.6°, azimuth 250°, 5.92 AU, magnitude −1.9, elongation 48°, in Leo
Satellites	built-in ISS TLE	51.64° inclination, 92.9 min period, apogee/perigee 420 / 417 km, ground track ±50 min
Time Scales	2026-10-01 12:00	JD 2461314.66667, MJD 61314.16667, JDE (TT) 2461314.66754, ΔT 75.5 s, LST 12:25:16, ISO week 2026-W40
Coordinates · Convert	39.9042, 116.4074	DMS 39°54'15.12"N 116°24'26.64"E, UTM 50S 449345.1 E 4417292.5 N, MGRS 50SMK4934517292, Geohash wx4g0bm6c
Coordinates · Distance	Beijing → Shanghai, 31.2304, 121.4737	Vincenty 1065.846 km, initial bearing 152.97°, final 155.93°; Haversine 1067.312 km, Δ -0.137 %
Coordinates · Area	rectangle 39.9100, 116.3900 – 39.9040, 116.4000	569072 m², 56.9072 ha, 853.607 mu, perimeter 3.0426 km

The Moon sits −5.4° below the horizon at 311° NW; Time Scales adds Unix 1790827200 and GAST 04:39:38; Beijing projected 100 km on a 45° bearing lands at 40.538021, 117.242036.

Reading the numbers and limits

Method limits.: Positions print to 0.1–1° (±1′ typical); rise and set are searched inside the selected local day; the phase name is the nearest eighth of the cycle while the illuminated percentage is continuous; the distance card names near perigee, apogee or mean. Distances are Vincenty with an iteration count and a spherical fallback at near-antipodal points; areas use spherical excess (<0.5% error).
Satellite predictions age.: Positions and passes come from your element set; the built-in ISS set is old and the panel warns until you press Update from CelesTrak. Passes need maximum elevation ≥10°; whether the satellite is sunlit against a dark sky is not modelled.
What it does not do.: No star chart, no ephemeris export, no time-zone conversion. For weekdays, date arithmetic and zone changes use the date calculator; for orbital dynamics, the Physics Sim; for other duration units, the time converter.

The clock behind the cards

The trap is the clock, not the coordinates: rise and set are searched from your device's midnight and printed in your device's zone, while the location bar moves only the observer. Keep the observer at Beijing and the date at 1 October 2026. A UTC+8 clock reads sunrise 06:10, sunset 17:57, day length 11h 47m; a UTC clock reads sunrise 22:11, sunset 09:57 and shows — for day length, because the sunset belongs to 1 October and the sunrise to 2 October. Match your device zone to the place, or convert the printed times afterwards.

Where it fits

Planning an evening outdoors

Enter the site and date: around Beijing on 1 October astronomical darkness runs 19:27 → 04:40, the planet table names what is up, and the Moon shows 76.3% illumination.

Coordinates in the field and on Chinese maps

A GPS fix is WGS-84, but AMap and Tencent expect GCJ-02 and Baidu expects BD-09; this Beijing point shifts by ≈555 m and ≈1375 m, half a block in map terms. The same tab emits DMS, DDM, UTM, MGRS, Web Mercator and a geohash, with per-provider map links.

Measuring and auditing

Beijing–Shanghai is 1065.846 km on the ellipsoid against 1067.312 km on the sphere; the default four-vertex plot is 569072 m² with a 3.0426 km perimeter. For logs, Time Scales turns one instant into Unix, JD, MJD, JDE, ΔT and ISO week.

References

Wikipedia: Twilight — twilight angles at −6°, −12° and −18°. en.wikipedia.org （访问日期：2026-10-01）
Wikipedia: Lunar phase — phase angle, illuminated fraction, eight names. en.wikipedia.org （访问日期：2026-10-01）
Wikipedia: Julian day — JD, MJD and the ephemeris JDE (TT). en.wikipedia.org （访问日期：2026-10-01）
Wikipedia: Restrictions on geographic data in China — WGS-84 → GCJ-02 and BD-09 shifts. en.wikipedia.org （访问日期：2026-10-01）
Wikipedia: Vincenty's formulae — ellipsoidal solutions, antipodal non-convergence. en.wikipedia.org （访问日期：2026-10-01）
Wikipedia: Simplified perturbations models — SGP4/SDP4 propagation behind TLEs. en.wikipedia.org （访问日期：2026-10-01）