The double-wheel chart is a screen that overlays another chart (outer wheel) on top of the natal chart (inner wheel) for comparison. It supports Transit, Progression, Solar Arc, Solar Return, Lunar Return, and Synastry, and its key feature is the ability to jump straight to that day’s chart with one click from a forecast list.
Prerequisite: The inner wheel uses the data entered and saved on the top page (input screen). When you open the page, “Natal x Transit (current time)” is displayed automatically (if a handoff from Person B or a transition from chart analysis exists, that takes priority). All setting changes trigger automatic recalculation.
Contents of this page
- 1. Choosing the inner and outer wheel
- 2. Date/time settings panel
- 3. Basic tab — inner/outer body comparison table and dispositors
- 4. Compatibility tab — aspect matrix
- 5. MP tab — 6 midpoint categories
- 6. Forecast tab (Transit / Progression)
- 7. Forecast 2-SA tab (Solar Arc)
- 8. Settings tab — display and calculation controls
- 9. Setting up Person B (compatibility)
- 10. Copy / PDF export
- 11. Useful things to know
1. Choosing the inner and outer wheel
The inner/outer wheel dropdowns are on the “Settings” tab.
Inner wheel (2 options)
| Option | Description |
|---|---|
| Natal (default) | Displays the natal chart on the inner wheel. |
| Midpoint | Hides the inner wheel’s bodies and aspect lines, and instead shows midpoint category bands (±2°) with labels (e.g. ☉/☽). Linked to the category switch on the MP tab. |
Outer wheel (6 options)
| Option | Date/time specification, etc. |
|---|---|
| Transit (default) | Year/month/day/hour/minute spinners + Current Time button |
| Progression | Same as above (target date/time for secondary progression) |
| Solar Arc | Year/month/day spinners + Today button |
| Solar Return | Year only |
| Lunar Return | Year + month |
| Compatibility (another person) | Specify the other person via 👤 Set Person B (Section 9) |
About the observation location: If a location has been saved under “Current Data” on the input screen, that location is used for the transit’s default date/time and observation location (coordinates/time zone).
2. Date/time settings panel
Use the “Date/Time Settings” panel floating at the bottom right of the screen to move the outer wheel’s date and time. Drag the header to move it; closing it with the ✕ makes a 📅 Date/Time Settings button appear at the top right (click it to show the panel again).
- Spinners (▲/▼): Click for ±1. Press and hold for continuous change, and the chart updates as it tracks the change (choose slow/medium/fast speed; medium is default). Day → month → year roll over/under automatically (accounting for end-of-month dates).
- Keyboard shortcuts: For Transit/Progression, A/S/D/F/G increase year/month/day/hour/minute by 1, and Z/X/C/V/B decrease them by 1. For Solar Arc, use A/S/D (+) / Z/X/C (−) to control year/month/day.
- Automatic recalculation: After you change a value, the chart recalculates automatically after a short delay (0.25 seconds).
3. Basic tab — inner/outer body comparison table and dispositors
A comparison table listing the inner and outer wheel positions for 23 bodies.
Meaning of the columns
| Column | Description |
|---|---|
| Display | Checkbox. Linked to the wheel, compatibility matrix, and forecast filtering. By default, 10 bodies + ASC/MC + North Node + Chiron are ON (can be overridden in “Bodies Used” on the settings screen). |
| Symbol / Body | Glyph and name. Nodes show the (T)/(M) calculation method, and Lilith shows (M)/(T)/(N). |
| Inner wheel (2 columns) | Sign symbol + degree (degrees/minutes or decimal). Retrograde is shown in red R. |
| Outer wheel (2 columns) | Same as above (distinguished with a light blue background). |
| Inner/outer declination | ± degrees. Out-of-bounds (beyond ±23.44°) is shown in bold red. When the outer wheel is Solar Arc, the outer declination column is hidden. |
| Inner/outer dodecatemoria | The dodecatemoria sign symbol. |
Dispositors (rulership chain)
Below the table, the dispositor chain for the inner wheel (and the outer wheel too, if outer wheel data exists) is displayed. Using modern rulers (Scorpio = Pluto, Aquarius = Uranus, Pisces = Neptune), the 10 bodies are linked as “body → ruler” chips and color-coded.
- Final (green) … A body residing in its own sign. The endpoint of the rulership chain.
- Mutual reception (yellow) … A pair of 2 bodies that occupy each other’s signs.
- Loop (red) … A cycle of 3 or more bodies detected when there is no final.
4. Compatibility tab — aspect matrix
A tab for checking the aspects between the inner and outer wheels in a grid. It can be used not just for compatibility (synastry) but with any outer wheel, such as Transit.
Aspect matrix
12 bodies (10 bodies + ASC/MC) run along both the rows and columns. Inner wheel bodies (symbol, sign, degree) are listed on the left edge, outer wheel bodies on the right edge, and the aspect symbol appears in the intersecting cell. Judgment uses only the 5 major aspects (Conjunction ☌ / Sextile ⚹ / Square □ / Trine △ / Opposition ☍), with the orb taken from the slider value on the Settings tab. Cell background colors are: Conjunction = purple, Trine = green, Sextile = blue, Square/Opposition = red.
Dodecatemoria matrix
Below that is a matrix showing the relationships between each body’s dodecatemoria signs. This one is judged purely by sign difference, not degree (same sign = conjunction, 2 signs apart = sextile, 3 = square, 4 = trine, 6 = opposition).
5. MP tab — 6 midpoint categories
A tab for viewing important midpoints (the midpoint of 2 bodies) organized by theme. Switch between them using the category buttons (with count badges).
| Category | Included midpoints (examples) |
|---|---|
| Life Core | ☉/☽ integration of masculine and feminine, ☉/ASC self-expression, ☉/MC social mission, ☽/ASC emotional expression, ☽/MC public emotion |
| Love | ♀/♂ sexual love, ♀/♃ happy love, ♀/♄ testing love, ♀/♅ sudden love, ♀/♆ idealized love, ♀/♇ intense love, and others |
| Success | ☉/♃ success, ☉/♅ originality, ♃/♅ great success, ♂/♃ drive, ☿/♃ intelligence, and others |
| Crisis | ☉/♄ hardship, ☽/♄ loneliness, ♂/♄ accidents, ♂/♇ intense destruction, and others |
| Mental | ☿/♄ focused thinking, ☿/♆ imagination, ☿/♇ insight, and others |
| Social | ♂/MC ambition, ♀/MC social charm, ♃/MC career advancement, and others |
The list shows the position (sign and degree) and orb (fixed at ±2°) for each midpoint, and below it, the Sabian symbol at the midpoint position (symbol text + explanation) is displayed as cards colored by category.
When the inner wheel dropdown is set to “Midpoint,” the band for the currently selected category is also shown on the wheel, linked to the tab.
6. Forecast tab (Transit / Progression)
Lists when moving bodies will form an exact aspect to the natal bodies.
Settable conditions
| Item | Options |
|---|---|
| Mode | Transit / Progression |
| Reference date | Date (default = today) |
| Direction | Future (default) / Past |
| Period | 10 days (all bodies) / 1 month (excluding the Moon) / 4 months (Mars and beyond) / 1 year (Jupiter and beyond) |
The orb is fixed at 1.0°. Click Calculate to display the list (narrowed to only the bodies checked on the Basic tab).
Reading and using the results
The list is a table of “date / time / natal body / aspect / moving body / position.” Times are unified to the natal time zone. Clicking a row switches to the double-wheel chart for that date and time and scrolls to it. Being able to instantly check an interesting hit on the wheel is the key feature of this tab.
7. Forecast 2-SA tab (Solar Arc)
A tab for viewing long-term turning points using Solar Arc. “Current age” and “current Solar Arc degree” are displayed at the top.
Settable conditions
| Item | Options |
|---|---|
| Display period | Now to 5 years later (default) / to 10 years later / to 20 years later / entire life (age 0-100) / custom (enter starting and ending age as numbers) |
| Orb | Numeric input from 0.1 to 3° (default 1.0°) |
Reading and using the results
Cards for each age appear as “Important Turning Points in Life” (■ Age ○ (YYYY-MM)), followed below by a full aspect list (age / date / natal body / aspect / SA body / orb / error). Clicking a row switches the outer wheel to Solar Arc and displays the double wheel for that date.
8. Settings tab — display and calculation controls
In addition to the inner/outer wheel dropdowns (Section 1), the following items are available.
| Item | Options | Default |
|---|---|---|
| Aspect display | Inner wheel / Cross (inner x outer) / Outer wheel / None | Cross |
| Exclude OOS | Checkbox (hides out-of-sign aspects) | OFF |
| Applying only | Checkbox (shows only applying aspects) | OFF |
| Degrees/minutes | ON = degrees/minutes (28°18′) / OFF = decimal | ON |
| Orb | Slider 0-10° (0.25 increments) | 3.00° |
| Spacing | Slider 2-12° (spacing to avoid overlapping body symbols) | 6.0° |
| Houses | Placidus / Koch / Whole Sign / Equal / Solar Sign / Solar House / Porphyry / Regiomontanus / Campanus / Morinus | Placidus |
| Node | True / Mean | True |
| Lilith | Mean / True / Natural | Mean |
There are 7 types of aspect lines on the wheel (Conjunction = purple, Opposition = red, Trine = blue, Square = red, Sextile = green, Semisextile = pale blue, Quincunx = pale purple), and the orb is shared across all of them. Changes to houses, node, and Lilith are synced bidirectionally with the settings screen (⚙).
9. Setting up Person B (compatibility)
- Clicking 👤 Set Person B at the top right opens the input screen in “Person B input mode.”
- Enter the other person’s birth data (or select from a saved chart).
- Returning to the double-wheel chart, the outer wheel automatically becomes “Compatibility (another person),” and the synastry chart is displayed.
You can then check the aspects between the two people using the matrix on the Compatibility tab.
10. Copy / PDF export
📋 Copy Wheel Only
Copies the wheel to the clipboard as a 900×900 PNG. The image has the name, date/time, location, house system (top left), outer wheel information (top right), and the app’s URL (bottom right) burned in. On environments where copying isn’t possible, it downloads automatically as “name_chart.png.”
📄 Wheel + Basic Data PDF
Downloads a single-page landscape A4 PDF (wheel on the left, basic data table on the right). The file name is “name_birthdate_double.pdf.”
11. Useful things to know
- Priority order for the display when opening the page: (1) Compatibility, immediately after setting Person B (2) If transitioning from chart analysis, that condition (a “← Back to Chart Analysis” link appears) (3) If neither applies, Natal x Transit (current time). Manually moving a spinner returns you to the normal mode in (3).
- Time zone validation: If the birth data has no time zone name or uses an old format, a warning appears and the calculation is halted. Please re-select the location from the list on the input page and save it.
- Time notation: Forecast times are unified to the wall-clock time of the natal time zone.
- Panel width: You can adjust the width by dragging the left edge of the data panel (320-800px).
- Settings sync: If you change settings on another tab or the settings screen, they are automatically applied when you return to this screen.
- URL parameters: ?tab=◯◯ lets you specify the starting tab. ?tab=hm redirects to the HM tab of the single chart.
- Dates BCE: Negative years are displayed as “N BCE”.