Astronomy Ephemeris Calculator: Explore the Solar System Through Time
Planets are constantly changing position, distance, apparent size and brightness. An ephemeris tells us how those properties change with time.
Four ways to follow a Solar System object
30 October 2026
Compare the brightness, distance, apparent size and sky position of Solar System objects on any date.
| Object | Magnitude | Distance | Apparent size | RA | Dec |
|---|---|---|---|---|---|
| Sun | -26.76 | 0.993420 AU | 1,932.44″ | 14h 15m 33.1s | −13° 35′ 14.6″ |
| Moon | -11.46 | 0.002444 AU | 1,961.94″ | 05h 52m 33.5s | +27° 43′ 18.8″ |
| Mercury | 2.03 | 0.700348 AU | 9.61″ | 15h 00m 42.8s | −19° 15′ 51.8″ |
| Venus | -4.18 | 0.276539 AU | 60.39″ | 13h 31m 57.4s | −15° 20′ 39.5″ |
| Mars | 0.82 | 1.446960 AU | 6.46″ | 09h 20m 41.9s | +17° 09′ 12.6″ |
| Jupiter | -1.99 | 5.411040 AU | 35.65″ | 09h 45m 00.9s | +14° 15′ 49.7″ |
| Saturn | 0.45 | 8.249520 AU | 19.48″ | 00h 37m 25.5s | +01° 06′ 25.1″ |
| Uranus | 5.61 | 18.424000 AU | 3.80″ | 04h 09m 40.9s | +20° 51′ 49.3″ |
| Neptune | 7.69 | 28.908500 AU | 2.35″ | 00h 08m 39.3s | — |
| Ceres | 8.46 | 2.183660 AU | 0.60″ | 07h 35m 52.5s | +23° 55′ 17.0″ |
| Vesta | 6.69 | 1.399630 AU | 0.52″ | 01h 14m 42.9s | −04° 24′ 24.0″ |
| Pluto | 14.59 | 35.500100 AU | 0.09″ | 20h 24m 20.2s | −23° 42′ 09.4″ |
Values are read from the JPL-derived ephemeris data used throughout Show Me The Sky.
Choose an object and explore
How does it change?
Venus — Magnitude
What do these parameters tell us?
Brightness and apparent size
A planet's appearance changes as both its distance and geometry relative to Earth and the Sun change.
The magnitude scale describes apparent brightness, while angular size describes how large an object appears in the sky.
Distance and elongation
One astronomical unit (AU) is approximately the mean Earth–Sun distance.
Elongation measures the apparent angular separation between an object and the Sun. It is especially useful when considering the visibility of Mercury and Venus.
The Solar System is a moving system
A planet does not have one fixed distance, apparent diameter or brightness. Those quantities continually change as Earth and the other planets move around the Sun.
Ephemerides turn that orbital motion into predictions we can use to plan observations and understand what we see through a telescope.
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