ClockAstronomical guide
How to Read ClockAstronomical's Interactive Zodiac Wheel
Read ClockAstronomical's zodiac wheel, planet markers, retrograde labels, filters, and forward or reverse time controls.
ClockAstronomical uses the zodiac as a clock face. Instead of hour and minute hands, ten markers show the calculated longitude of the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto for one UTC instant. Playback then redraws those markers as the simulated time changes.
This interactive zodiac wheel is intended to make one-dimensional ecliptic longitude easier to see. It does not show where to look above your local horizon, and it does not interpret the positions.
Start at 0° Aries
The circle contains twelve equal 30° sectors. The boundary at 12 o’clock is 0° Aries, and longitude increases clockwise:
| Clockwise longitude | Sign | Degree range shown in the table |
|---|---|---|
| 0° to less than 30° | Aries | 0° to less than 30° Aries |
| 30° to less than 60° | Taurus | 0° to less than 30° Taurus |
| 60° to less than 90° | Gemini | 0° to less than 30° Gemini |
| … | … | … |
| 330° to less than 360° | Pisces | 0° to less than 30° Pisces |
The two-letter sign names sit near the middle of their sectors. In other words, the Aries boundary is at the top; the Aries label itself is centered farther clockwise. Five-degree tick marks help estimate a marker’s location, while the Planet Degree Table supplies the rounded numeric reading.
A zodiac wheel with planets therefore shows the same positions as the table in a different form. The wheel is spatial; the table formats the values to two decimal places. Both come from one calculated snapshot, and the formatting does not imply 0.01° accuracy.
Read a planet marker
Each marker has a two-letter body label and sits at the body’s calculated
0–360° longitude. A label ending in R uses the retrograde accent color. No
suffix means the tool shows no retrograde label. For Mercury through Pluto,
that follows the app’s before-and-after motion test; the Sun and Moon are
deliberately returned without running that test.
When multiple bodies are close, ClockAstronomical may move their labels outward at different radii and connect them back with thin leader lines. The circular marker remains at the calculated angle. This layout rule preserves the longitude while making crowded text easier to read.
The grouping is purely visual. It does not declare a conjunction, aspect, alignment, or other relationship. To compare the numbers, open the degree table instead of inferring an exact separation from label spacing.
That distinction is useful when people use phrases such as graphical planetary positions or visual planetary positions. The graphic encodes longitude faithfully, but typography may be displaced for legibility.
Move the clock through time
The playback controls turn a static snapshot into a planetary motion visualization:
- Now returns to the device’s current instant, switches to 1×, and starts playing.
- Play and Pause start or stop the simulated clock without changing the selected instant unexpectedly.
- Rewind 10× and Forward 10× run simulated time at ten times the wall-clock rate in the chosen direction. They are continuous speeds, not ten-day step buttons.
- Custom rewind and Custom forward reveal a positive whole-number speed. Use the minus and plus controls, or type a value and apply it.
- Entering a value in Date and time (UTC) jumps directly to that instant and pauses, making it easier to inspect a stable result.
When the chart is visible and keyboard focus is not inside a button, field, or link, the Space bar also toggles Play and Pause. At either supported date-range boundary, outward playback stops exactly at the endpoint; the next Play action resumes inward.
This is how ClockAstronomical depicts planets moving through the zodiac. There are no drawn orbital paths or motion trails. The application repeatedly calculates new longitudes and redraws the markers for the simulated timestamp. Thus animated planetary positions means a sequence of computed snapshots, not an animation of physical planet orbits around the Sun.
Isolate the bodies you want to compare
Open Planet filters to hide or show individual bodies. The interface also offers two convenience groups:
- Inner planets: Sun, Moon, Mercury, Venus, and Mars;
- Outer planets: Jupiter, Saturn, Uranus, Neptune, and Pluto.
Those are interface labels, not a formal scientific classification. Hiding a body removes it from both the wheel and table, but does not change the selected time or the underlying calculation. Filters are not stored in a share link.
The filters are especially useful when slow outer-body movement would otherwise be hard to notice among faster markers. Select a date, keep only the bodies relevant to your comparison, choose a safe speed, and pause at any point to read the table.
What similar names mean here
People describe this kind of interface in several ways. In ClockAstronomical:
- interactive planetary positions means the date, direction, speed, and visible bodies can be changed;
- planetary positions visualization means a wheel and table share the same calculated longitudes;
- a zodiac planet visualizer or astrology planet visualizer means the longitude is labelled with tropical zodiac signs, without a horoscope;
- an interactive zodiac planet chart emphasizes the 12-sector wheel;
- an interactive planetary position chart emphasizes that the markers and numeric result respond to the time controls.
These phrases do not add features. ClockAstronomical remains one Western-style, tropical, geocentric longitude view. It has no houses, ascendant, aspects, sidereal mode, natal comparison, or predictive reading.
A useful before-and-after exercise
Use Mercury for a sequence that is short enough to explore. At ClockAstronomical
commit 6c4fcf5 with Astronomy Engine 2.1.19, the app gives this rounded
pair:
| UTC instant | Mercury position | Motion label |
|---|---|---|
| 5 April 2024, 12:00 | Aries 26.50° (26.50° longitude) | R |
| 15 April 2024, 12:00 | Aries 19.91° (19.91° longitude) | R |
Enter the first instant, filter the view to Mercury, and note its marker. For
an exact comparison, enter the second instant directly. To animate the span,
return to the first instant, choose Custom forward, enter 100000, and
play for roughly nine wall-clock seconds before pausing; at that multiplier,
ten simulated days take about 8.64 seconds. Use the date field afterward to
settle on the exact endpoint. The decreasing longitude makes the reverse
motion visible without pretending the playback rate is physical speed.
You can then rewind the simulation or play it forward again. The retrograde guide explains the motion label and its one-day numerical window. Remember that the tool is redrawing positions, not showing a path through the local night sky.
A zodiac wheel is not a sky map
A local sky map requires an observing location and normally uses altitude and azimuth to show direction and height above the horizon. ClockAstronomical asks for no location and calculates neither quantity. It cannot tell you whether a body is visible, when it rises, or which direction to face.
The wheel also should not be read as a plan view of the solar system. It is an Earth-centered angular chart of tropical ecliptic longitude. For the numeric coordinate and calculation details, continue with What Is a Planetary Ephemeris?.
Primary sources and methodology
- JPL Horizons system manual for the distinction among reference frames and observer-centered ecliptic coordinates.
- Astronomy Engine project documentation for the library used to calculate the underlying positions.