The chart wheel explained: ten things on Robin’s wheel

A chart wheel looks like a dartboard drawn by an astronomer, and the first look is the worst. This guide takes it apart in ten pieces. Each piece comes with its value from one real chart: Robin’s, an example person born 8:30am on 14 March 1990 in Chicago.

Everything below describes what Charthood’s wheel draws, because other tools make different choices. It is drawn straight from the engine behind our free birth chart calculator.

1. The outer ring is the twelve signs

The coloured band round the edge is the zodiac, cut into twelve 30° slices, each with its sign’s glyph in the middle. The tint is the element: warm for fire, olive for earth, pale blue for air, grey-green for water. Signs run anticlockwise, the way a printed chart has always shown them.

Robin’s Sun is at 23°44′ Pisces, so it sits in a water slice of the ring, the Pisces one. The Ascendant, 21°12′ Taurus, sits on the left edge, so the Taurus slice straddles the 9 o’clock line.

2. Spokes mark the house cusps

Twelve lines run from the ring towards the middle. Each is the start (the cusp) of a house, and the number inside the wheel names it. Four are drawn heavy: the 1st, 4th, 7th and 10th. The rest are thin.

Houses are not equal slices, at least in Placidus, which is the default. Robin’s narrowest house is the 8th, at 20.9°. The widest is the 12th, at 48.6°. Our houses guide explains why, and the Placidus vs Whole sign study shows what changes if you pick another system.

3. Why is the rising sign always on the left?

Because the wheel is a view of the sky from the birthplace, with east on the left. The Ascendant is the degree of the zodiac rising over the eastern horizon at the birth minute, so Charthood turns the wheel until that degree sits at 9 o’clock. It is labelled AC.

Opposite it, at 3 o’clock, is the Descendant, the degree setting in the west. It is the start of the 7th house and it has no label of its own: it is the heavy line facing AC. Robin’s are 21°12′ Taurus and 21°12′ Scorpio.

4. MC and IC: the top and bottom of the sky

The Midheaven (MC) is where the zodiac crosses the local meridian, the line from due south to due north overhead. The IC sits opposite, below your feet. Robin’s MC is 29°37′ Capricorn, and the IC is 29°37′ Cancer.

On Charthood’s wheel the MC is not at 12 o’clock. We turn the wheel by the Ascendant, not the MC, so the MC lands wherever the geometry puts it: for Robin, about 22° from the top. Only the MC is labelled; the IC is the heavy line on the other side.

5. Planet glyphs, and a tick at the true degree

Each planet and the North Node gets a glyph on a ring inside the houses. A small tick on the inner circle, just under the zodiac band, shows its exact degree, because glyphs are wide. When two sit within 7.5° of each other, the wheel nudges them apart. The tick stays honest; the glyph moves.

Robin’s Sun is shifted the furthest, by 1.6°. In all, 7 of Robin’s 11 glyphs are nudged. The Sun at 23°44′ Pisces and Mercury at 19°30′ Pisces are the pair that need room.

6. The small ℞ marks a retrograde planet

A tiny accent-coloured ℞ sits beside a glyph when the planet’s daily motion is negative at the birth minute. It is an apparent effect of Earth overtaking or being overtaken by that planet.

Robin has one retrograde planet: Pluto at 17°37′ Scorpio. It is barely backwards: 0.01° a day. The North Node never gets a ℞, since it drifts backwards on average. See our retrograde guide for the rest.

7. Aspect lines join the planets in the middle

The web inside the inner circle is the aspects. Blue lines are easy angles (trines and sextiles, with sextiles dashed). Red lines are tense ones (squares and oppositions). A line within 2° of exact is drawn thicker and darker; looser ones are thinner and paler.

Robin’s wheel carries 14 lines: 5 red and 9 blue (4 of them dashed sextiles). 4 of them are bold. The tightest is Sun sextile Saturn, 0.48° from exact. For how to read them, see the aspects guide.

8. The outer track shows another sky

Outside the zodiac band the wheel can carry a second ring: a different set of positions in the accent colour, each with a short tick and a glyph. It is used for today’s transits, for a partner’s chart, or for the sky at any moment. This post’s picture uses the sky at 12:00 UTC on 28 October 2026.

On that day transiting Saturn is at 9°30′ Aries, which falls in Robin’s 12th house. Jupiter, at 23°52′ Leo, falls in the 4th. The outer track draws positions only. It has no ℞ marks and no aspect lines, so you do the matching by eye, or read the list on the page.

9. What do the little ticks around the ring measure?

Degrees. Along the inner edge of the zodiac band there is a short tick every 5°, a longer one at 10° and 20°, and none at 0°, because the sign line is already there. There are no numbers on the wheel itself. Exact positions are in the list beside it.

Robin’s Sun is at 23°44′ of Pisces: past the tick at 20°, 1.3° short of the next. The planet’s own tick shows the same spot.

10. What does the wheel leave out?

Less than you might think, but some things are deliberately missing.

• No South Node. Charthood draws the North Node only; the South Node is always 180° away.
• No asteroids or Chiron. The wheel carries the Sun, Moon, eight planets, the North Node and the two angles.
• Only five aspects. Conjunction, sextile, square, trine and opposition. No quincunxes or semi-sextiles.
• No houses without a birth time. Without it Robin’s wheel would show 11 points instead of 13, and no spokes, AC or MC.

The house system is named in the line under the wheel, not on the wheel itself: for Robin, Placidus houses.

Common mistakes

• Expecting the Midheaven at the top. On this wheel it is where the geometry puts it.
• Reading a glyph’s spot as its degree. Trust the tick. Crowded glyphs get nudged.
• Counting lines as importance. A pale thin line is a loose aspect. Start with the bold ones.
• Mixing up the angles. Only AC and MC are labelled. The Descendant and IC are the heavy lines opposite.
• Comparing wheels from different tools. Rotation, house system and aspect set vary. The ecliptic, the Sun’s path the signs are cut from, does not.

Now you can name every mark on Robin’s wheel. To put it to use, work through the seven-step birth chart guide, or open the wheel for your own chart. The positions underneath come from astronomy-engine.