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TOPOCENTRICA
I. Introduction
Topocentrica is an implementation of the Polich & Page Topocentric Ascensional Transit System, first published in 1964. It provides precision transit analysis using equatorial coordinates, topocentric house poles, and the concept of Distance from Meridian in Oblique Ascension (DMO).
Unlike ecliptic-based transit methods that measure contacts in zodiacal longitude, this system operates in the equatorial plane, measuring how far a planet has traveled through its diurnal arc relative to the meridian. Every planet is located by its angular distance from the MC or IC, expressed as a fraction of its own semi-arc — yielding a universal 0–90° coordinate that makes mundane position directly comparable across declinations.
This application was built for practitioners already familiar with house systems, aspects, and primary directions. It assumes working knowledge of RA, declination, and the celestial sphere.
II. Core Doctrine
Distance from Meridian (DMO)
The foundational measure of the topocentric system. DMO expresses a planet's position as the ratio of its meridian distance (MD) to its semi-arc (SA), scaled to 90°:
DMO = (MD / SA) × 90°
A planet exactly on the MC or IC has DMO = 0°. A planet exactly on the ASC or DSC has DMO = 90°. The range 0–90° maps uniformly across all four quadrants regardless of a planet's declination or the observer's latitude.
Hour Angle (HA)
The angular distance of a celestial body westward from the meridian, measured along the equator:
HA = (RAMC − RA) mod 360°
HA = 0° at the MC, increasing westward. HA = 180° at the IC. The four quadrants are defined by HA ranges:
Q4 (Houses 7, 8, 9): Above horizon, west — HA 0–90°
Q3 (Houses 4, 5, 6): Below horizon, west — HA 91–180°
Q2 (Houses 1, 2, 3): Below horizon, east — HA 181–270°
Q1 (Houses 10, 11, 12): Above horizon, east — HA 271–360°
Oblique Ascension & Oblique Descension (OA / OD)
OA is the equatorial degree rising at the eastern horizon at the moment a planet crosses it, computed under the planet's own topocentric pole. OD is the corresponding degree at the western horizon. These are the fundamental values for computing equatorial aspects in the Polich & Page framework.
OA = RA − AD | OD = RA + AD
where AD (Ascensional Difference) is derived from the planet's declination and its topocentric pole.
Topocentric Poles
Each house cusp in the topocentric system has a unique pole — the geographic latitude at which that cusp's ecliptic degree would be exactly on the horizon. Planets inherit their pole from their house position. This is what distinguishes topocentric from Placidus: Placidus uses the observer's latitude uniformly; topocentric uses a pole specific to each planet's actual altitude in the local sphere.
Semi-Arc (SA)
The angular measure from horizon to meridian for a given declination at a given latitude. The diurnal semi-arc (DSA) runs from the eastern horizon through the MC to the western horizon. The nocturnal semi-arc (NSA) runs beneath. A planet above the horizon uses DSA; below uses NSA.
III. Chart Modes
ASC (Ascensional Chart)
The native Polich & Page view. Planets are placed on the wheel by their DMO within their quadrant. The four angles are fixed: ASC at 9 o'clock, MC at 12 o'clock, DSC at 3 o'clock, IC at 6 o'clock. House sizes reflect the equatorial semi-arc proportions at the observer's latitude.
This is the primary working chart of the application. All DMO analysis, aspect computation in OA/OD space, and directed transposition features operate in this mode.
ECL (Ecliptic Chart)
Traditional ecliptic zodiac wheel with selectable house systems:
ASP — Aspect lines connecting planets on the wheel
TICK — DMO degree tick marks (0°, 10°, 20°, 30° markers in each house)
RAD — Radial spoke lines from center to each planet
CUSP — House cusp ring showing OA/OD values at each cusp, with ecliptic longitude labels
DEC — Decanic sectors: activates the fractal subdivision system (decans, dodekatemoria, dodek-decans)
V. The Decanic Fractal System
When DEC is active, the cusp ring reveals a layered subdivision system that becomes progressively visible as you zoom in:
36 Decans (visible at base zoom)
Traditional 10° divisions of the 360° wheel, numbered 1–36. Three decans per house. Each decan occupies the full width of the cusp ring and displays its DMO range at zoom ≥ 2.5×.
144 Dodekatemoria (zoom ≥ 3×)
Four subdivisions per decan, 12 per house, each spanning 2.5°. Labeled 1–12 within each house following the fractal house journey rule: the dodek number cycles through the house sequence offset by the starting house. Each dodek carries:
Elemental coloring — Fire (red), Earth (gold), Air (blue), Water (green) based on sign association
Planetary joy glyph — the traditional planetary ruler displayed outside the dodek ring
DMO range — shown at zoom ≥ 8×, alternating above/below the dodek number
432 Dodek-Decans (zoom ≥ 12.5×)
Three sub-decans per dodek, each ~0.833°. Numbered sequentially within each dodek. These provide the finest level of mundane subdivision, with their own DMO range labels alternating sides to prevent overlap.
Use the mouse wheel to zoom (1× to 100×, logarithmic) and click-drag to pan at zoom > 1×. Double-click resets the view.
VI. The Four RAMC Transpositions
The heart of the Polich & Page transit methodology. By shifting the natal RAMC, we transpose the entire natal chart into a new frame while overlaying live transits at their actual current positions. This reveals directed contacts in real-time.
RADIX
Baseline — no shift. The natal chart at its original RAMC. Transit planets overlay at the event's actual RAMC. This is the standard biwheel view.
TEMPORAL
The natal RAMC is shifted forward (direct) or backward (converse) by the solar arc: one degree of RAMC rotation for each year of life elapsed.
This is the primary directed DMO chart. Natal planets retain their birth RA and declination but are recalculated for DMO, house, quadrant, and pole under the new RAMC. Transit planets remain at their actual sky positions against the actual current RAMC.
The result is a living directed chart: you see where your natal significators have progressed to in mundane space, and which transiting planets are contacting those directed positions right now. Combined with the decanic fractal system, this reveals directed contacts at extraordinary precision — down to sub-degree dodek-decan sectors.
Toggle between Direct (RAMC advances) and Converse (RAMC retreats) using the D/C buttons.
LOCAL
The natal RAMC is shifted by the geographic longitude difference between the birthplace and the event location. This is a mundane relocation: the natal chart recast for a different place on Earth.
Local RAMC = Natal RAMC + (ΔLongitude in time)
FULL
The combined time + space transposition: solar arc shift plus longitude shift applied together. This is the most comprehensive transposition, showing the directed chart as it would appear at the event location.
Full RAMC = Natal RAMC + Solar Arc + ΔLongitude
VII. Speculum & Aspects
Speculum Columns
Planet — Planet glyph and name
DMO — Distance from Meridian (degrees, minutes, seconds)
Q — Quadrant (Q1–Q4, color-coded)
H — House number (1–12)
Pos — Above (▵) or below (▿) the horizon
DSA — Distance in Semi-Arc (degrees)
Pole — Topocentric pole of the planet
Ecl.Lon — Ecliptic longitude (sign + degree)
RA — Right Ascension
Decl — Declination
OA — Oblique Ascension
OD — Oblique Descension
AD — Ascensional Difference
Aspect Types
Ecliptical Transits — Traditional aspects measured in ecliptic longitude
Equatorial OA/OD — Harmonic aspects computed in OA space (above horizon) or OD space (below horizon). These are the primary topocentric aspects.
Ascensional Transits — Transit-to-Transit (T→T), Natal-to-Natal (N→N), and Transit-to-Natal (T→N) contacts in equatorial space
Symmetric Aspects — Antiscio / mirror aspects based on adjacent-quadrant DMO proximity. Two planets at equal DMO in adjacent quadrants form a symmetric contact.
Resonance Scoring
Each aspect row displays a resonance score (1–4 dots) indicating how many independent aspect spaces confirm the contact. A single ecliptical aspect scores 1; if the same pair also aspects in OA/OD, ascensional, and symmetric space, it scores up to 4. Higher resonance suggests greater mundane significance.
Perfection
The PERF column shows aspect lifecycle: A (applying) with percentage toward exactitude, or S (separating) with percentage of decay. This updates in real-time during LIVE mode.
VIII. Orb System
Orbs follow a soft power law based on harmonic number:
Orb(h) = 25′ × h−0.6
This produces: H1 ≈ 25′, H2 ≈ 17′, H3 ≈ 13′, H7 ≈ 8′, H10 ≈ 6′. The taper is gentler than inverse-linear but still discriminates meaningfully between low and high harmonics.
Master scale (0.10× to 3.00×) — scales all orbs proportionally
Individual sliders (H1–H12) — fine-tune each harmonic
Symmetric orb — separate slider for antiscio/mirror contacts
Orb snapshots are stored with each research event, enabling reproducible statistical analysis across sessions.
IX. Time Features
LIVE Mode
Real-time chart updating at 50ms intervals with millisecond UTC clock display. The chart continuously recalculates all planet positions, aspects, and directed contacts. Essential for timing elections, observing exact perfection moments, and real-time event work.
DYN (Dynamic Mode)
Animated time-lapse with full playback controls: play/pause, step forward/back, variable speed (days per frame), and a scrubbing slider. Watch aspects form and dissolve over time. Useful for identifying windows of activity and understanding temporal patterns.
CHRON (Chronoscope)
A stopwatch/lapwatch for capturing precise moments. Start the chronoscope, then mark "laps" to snapshot the current chart state with timestamp and coordinates. Each lap can be named and saved to the research database. Designed for real-time event timing — births, elections, synastry snapshots.
X. Research & Logging
The LOG button captures the current moment as a research event, storing the full chart data along with the current orb settings snapshot. Events are persisted in SQLite and designed for statistical frequency analysis.
The research system uses orb-weighted scoring: each event's aspects are weighted by proximity to exactitude (weight = 1 − actual_orb / max_orb). Tight-orb events score near 1.0; barely-in-orb events score near 0. This allows meaningful statistical comparison across different orb settings and research sessions.
XI. Chart Library & Management
The Library panel (left sidebar) stores all saved charts in a hierarchical folder structure backed by SQLite. Charts persist across sessions and can be organized, searched, and loaded into any ring slot.
Saving a Chart
Cmd+S (Mac) or Ctrl+S (Windows) — keyboard shortcut to save the current RADIX chart.
Alternatively, click the SAVE button in the header toolbar.
If the chart is new (unsaved), a dialog prompts for a name. If it already exists in the library, it overwrites silently.
Saved charts store: name, date/time (UTC), latitude, longitude, timezone, Rodden Rating, and all computed positions at the moment of save.
Tip: Save frequently when experimenting with rectification — each save creates a distinct library entry you can compare later.
Folder Organization
Create folder — right-click in the library panel or use the folder icon. Enter a name and press Enter.
Rename — double-click a folder name to edit it inline.
Delete — right-click a folder and choose Delete. Charts inside are moved to the root level, not destroyed.
Drag-and-drop — click and drag any chart entry onto a folder to move it. Drag a chart out of a folder back to root.
Folders can be nested one level deep.
Loading Charts into Slots
RADIX (natal) slot — double-click a chart in the library, or select it and click LOAD. This sets the inner wheel.
TRANSIT slot — with a chart loaded in RADIX, right-click a second chart and choose “Load as Transit” to populate the outer ring.
The header shows which chart occupies each slot, with the chart name and date.
Biwheel & Triwheel
Biwheel — load a natal chart in the RADIX slot and a second chart (transit, return, or another nativity) in the TRANSIT slot. The inner ring shows natal positions; the outer ring shows the second chart.
Triwheel — the TRIWHEEL toggle adds a third concentric ring. Load a third chart via the Triwheel slot selector. Useful for comparing natal + directed + transiting positions simultaneously.
Each ring is independently color-coded. Aspect lines can be drawn ring-to-ring or within a single ring, controlled by the aspect-line toggles.
ADB (Astro-Databank) Charts
The library ships with 4,800+ celebrity and historical nativities from the Astro-Databank public dataset.
These appear in a dedicated ADB folder. Browse alphabetically or use the search bar to filter by name.
Each ADB entry includes the published Rodden Rating (AA through DD, X, XX) indicating data reliability.
ADB charts can be loaded into any slot just like user-saved charts.
Rodden Rating System
AA — from birth certificate or official record.
A — from memory of the native or family member.
B — from biography or autobiography.
C — caution, original source unknown.
DD — conflicting data, two or more sources disagree.
X — no time of birth available (noon chart).
XX — no date of birth available.
The Rodden Rating is displayed next to the chart name in the header. Always check the rating before drawing conclusions about house cusps or angles.
XII. Atlas & Location
Accurate geographic coordinates are essential — they determine house cusps, semi-arcs, ascensional differences, and every topocentric calculation in the system.
City Search
Click the location field in the header to open the Atlas panel.
Begin typing a city name — results appear after 2+ characters, filtered by population-weighted relevance.
Select a result to auto-fill latitude, longitude, and timezone.
Interactive Map Picker
Click the map icon to open an interactive map view.
Click anywhere on the map to set coordinates directly — useful for rural birth locations or specific addresses.
Saving & Recent Locations
Favorites — click the star icon next to any location to save it for quick access.
Recents — the atlas remembers your recently used locations, listed at the top of search results.
How Location Affects the Chart
House cusps — latitude determines the oblique ascension of each cusp. At extreme latitudes, some houses become very large or very small.
Semi-arcs — the diurnal and nocturnal semi-arcs depend on latitude. These govern DMO values and all topocentric calculations.
Pole of the planet — each planet’s topocentric pole is a function of its declination and the observer’s latitude.
Longitude shifts the RAMC (sidereal time), rotating the entire house framework around the ecliptic.
XIII. Returns — Solar, Lunar & Planetary
Returns mark the moment a transiting body returns to its exact natal position. The app computes these to sub-arcsecond precision using bisection search over the Swiss Ephemeris.
Solar Return
Tropical Solar Return — Sun returns to natal tropical longitude. The standard Western return.
Sidereal Solar Return (SSR) — Sun returns to natal sidereal longitude.
Precessed (PSSR) and Reversed (RSSR) variants also available.
Select the return year from the year selector. The computed return chart loads into the transit slot, creating a biwheel with the natal chart.
Lunar Return
The Moon returns to its natal longitude approximately every 27.3 days.
Tropical, Sidereal (SLR), Precessed (PSLR), and Reversed (RSLR) variants.
Anlunar — Moon returns to the Sun’s natal position (a solar-lunar hybrid return).
Quotidian — daily Moon return, used as a daily timing refinement.
ALL YEAR view — displays all 13 lunar returns for the selected year. Click any entry to load that return chart.
Planetary Returns
Available for Mercury, Venus, Mars, Jupiter, and Saturn.
Mercury and Venus return roughly yearly; Mars every ~2 years; Jupiter every ~12 years; Saturn every ~29.5 years.
Relocation Returns
Cast a return chart for a different location using the coordinate input boxes on the return pane.
The USE HEADER button copies the current header coordinates into the relocation fields.
Relocated returns shift house cusps and angles while keeping planetary positions the same.
Relocated solar returns are a cornerstone of the Colucci/Volguine predictive method — moving to a location where a benefic is angular in the return chart.
XIV. Primary Directions
Primary directions are the oldest and most precise predictive technique in Western astrology, based on the apparent diurnal rotation of the celestial sphere.
Theory
A promissor (signifying planet) is carried by diurnal rotation toward the position of a significator (receiving planet or cusp).
The arc of direction is the equatorial degrees between them.
An arc-to-time key converts this arc into years of life.
Six Direction Systems
Placidus — semi-arc proportional houses. The dominant system from the 17th century onward.
Regiomontanus — equatorial houses. Directions measured by hour-angle distance.
Campanus — prime vertical houses.
Topocentric — Polich-Page system (1964). Each planet has its own pole. The native system of this application.
Alcabitius — semi-arc houses divided by equal time intervals. Medieval standard.
Equal — 30° from the Ascendant. Simple ecliptic longitude arcs.
Four Arc-to-Time Keys
Ptolemy — 1° = 1 year. The simplest and oldest.
Naibod — 1° = 1.0147 years (mean daily solar motion in RA: 0°59′08″).
True Solar Arc — actual daily solar motion on the native’s birthday.
Cardan — 1° = 1.0027 years (mean sidereal day).
Direct vs Converse
Direct — promissor carried forward (westward) by diurnal rotation.
Converse — significator carried backward (eastward). Both computed simultaneously.
Direction Modes
Natal-to-Natal — both from birth chart. The standard mode.
Natal-to-Event — natal significators directed to event positions.
Event-to-Natal — event positions directed to natal significators.
Event-to-Event — both from the event chart.
EVENTS Sub-tab
Record life events with dates and descriptions.
The app computes which primary directions were active at each event date across all selected systems and keys.
Starkman scoring — ranks directions by closeness of arc to event date, weighting by aspect type and planet significance.
RECTIFY Sub-tab
Enter known life events with approximate dates.
The rectification engine tests a range of birth times and scores each candidate by how precisely its directions align with events.
Results ranked by composite score — best-fitting birth time at top.
Primary directions are the gold standard for rectification — house cusps move roughly 1° every 4 minutes of clock time, making them highly sensitive to birth time.
XV. Circumambulations — Hellenistic Life Timing
Circumambulations (also called “distributions”) are the primary Hellenistic method for timing life events. A releaser is directed through the zodiacal bounds at the rate of ascensional times.
Each uses different selection criteria for determining the planet or point that “releases” life.
Select an algorithm and the app highlights which planet qualifies and shows the reasoning chain.
MASTER Sub-tab — Alcochoden
The Alcochoden is the planet with the most dignities at the degree of the Hyleg.
Montulmo method — classical algorithm. Its minor/middle/major years give life expectancy.
Synthesis method — averages results from multiple Hyleg algorithms.
LISTING Sub-tab
Full circumambulation listing: the Releaser advances through bounds at the ascensional time rate.
Sect scoring, left/right rays, OA distortion, neutralization, and bounds overlay all displayed.
XVI. Profections
Profections advance the chart by one sign per year from a starting point, activating the ruler of the profected sign as time-lord.
TIMELINE Sub-tab
Annual profection — one sign per year from ASC (or any chosen point).
Monthly sub-profections — three systems: solar monthly, equal monthly, lunar monthly.
Daily sub-profections — three rates for daily granularity.
Nested drill-down — click a year to expand months; click a month to expand days.
Profect from any point — ASC, MC, Lot of Fortune, Lot of Spirit, or any planet.
TRANSMISSIONS Sub-tab
Valens’ whole-sign transmissions — when a planet profects into the sign of another planet, it transmits its significations.
MC and Lot of Fortune included alongside the seven traditional planets.
CONTINUOUS Sub-tab
Degree-precise profections — continuous advancement at 30°/year.
Exact calendar dates for sign ingresses, bound ingresses, and aspect events.
Biwheel click-through — click any event to load it as a biwheel.
Profections set the annual theme, circumambulations refine it, and transits trigger specific events. Layer all three for a complete Hellenistic predictive picture.
XVII. Ascensional Times
Ascensional times measure how long each sign takes to rise above the horizon. They are the foundation of all ancient timing techniques.
SIGNS
OA of each sign at the native’s latitude, with ruler, cumulative OA, and long/short classification.
PERIODS
7 × 12 fraction table mapping planetary periods across signs.
COMBINATIONS
Three cross-reference tables for advanced timing analysis.
FRACTIONS
Climacteric convergence finder — scans for years where multiple fraction-based methods converge.
XVIII. Ingresses & Transits
Transits scored by tension and filtered through active time-lords, following the Hellenistic principle that transits only manifest what the current time-lords signify.
EVENT Sub-tab
Tension scoring — based on aspect type, planet nature, speed, and proximity to exact.
Time-lord filtering — transits by the active profection/circumambulation lord are promoted.
Ancient delineations — from Dorotheus, Orpheus fragments, and Pseudo-Valens.
Star classification by path: Enlil (dec > +17°), Anu (−17° to +17°), Ea (dec < −17°).
~49 stars with Babylonian names and modern identifications.
OMENS
95+ Enuma Anu Enlil omen delineations with 28 phenomenon types auto-detected.
Omen texts include modern star identifications in parentheses.
ECLIPSES
FIND — search by date range, type, and location.
CYCLES — 16 eclipse cycles from Pentalunex (5 months) to Tetradia (7,248 months).
NATAL — eclipses aspecting the natal chart.
RESEARCH — degree search, Saros-Inex decomposition, cycle chains, Saros book.
XX. Epoch — Trutine of Hermes
The Trutine posits that at conception, the Moon occupied the degree of the birth ASC (or DSC), and the conception ASC occupied the degree of the birth Moon.
Four rules govern the calculation depending on lunar altitude and phase at birth.
Multiple candidates are generated and scored on internal consistency.
Higher-scoring candidates imply a specific birth-chart ASC, aiding rectification.
XXI. Astrolabe View
A fully interactive digital astrolabe with two projection modes.
Planispheric — standard stereographic projection. Plate shows altitude/azimuth circles; rete overlays ecliptic and star pointers.
Universal (Saphea) — Saphea Arzachelis, usable at any latitude without plate change.
Both raw count and weighted score displayed in frequency tables.
Orb settings and master scale stored with each event for reproducibility.
XXIV. Export & Bug Reports
PNG — 4× resolution for print quality.
JPG — compressed, suitable for web sharing.
SVG — scalable vector, ideal for publication.
Bug Report — submits chart state + diagnostic info. Use the BUG button in the header.
XXV. Keyboard Shortcuts & Navigation
Cmd+S / Ctrl+S — save chart.
Mouse wheel — zoom (1× to 100×, logarithmic, centered on cursor).
Click-drag — pan when zoomed in.
Double-click — reset zoom and pan.
XXVI. Heliocentric Mode
View from the Sun’s perspective. Moon, ASC, MC, and houses are hidden.
Heliocentric aspects reveal different geometric relationships between planets.
Nodes and apsides (perihelion/aphelion) displayed as fixed orbital reference points.
XXVII. Phase Tab — Heliacal Phenomena
Heliacal rising — first morning visibility above eastern horizon before sunrise.
Heliacal setting — last evening visibility above western horizon after sunset.
Acronychal rising — planet rises as Sun sets (opposition region).
Arcus visionis computed per planet, accounting for magnitude, extinction, and latitude.
In Hellenistic astrology, a planet making its heliacal rising (phasis) was at peak power — “appearing” to announce its significations. Many ancient timing techniques use phasis as triggers.
Topocentrica reconstructs the full scope of pre-modern astronomical calculation — from Babylonian observation logs through Hellenistic time-lord systems to medieval primary directions — unified in a single topocentric framework. Every algorithm is sourced from the historical literature and implemented with modern computational precision. Built by Cameron Cassidy.
Topocentric Astrology
A comprehensive treatise on the Polich & Page Topocentric Ascensional Transit System, covering its astronomical foundations, geometric theory, computational methods, house division, aspects, primary directions, and predictive techniques. Based on the 1964 publication by Wendel Polich and A.P. Nelson Page of Buenos Aires.
I. The Celestial Sphere
All positional astronomy begins with the celestial sphere — an imaginary sphere of infinite radius centred on the observer, onto which every celestial body is projected. Though physically meaningless (stars are at vastly different distances), the sphere provides the indispensable coordinate framework for measuring directions in the sky.
Fundamental Planes & Points
Celestial Equator — The projection of Earth's equator onto the sphere. Divides the sky into northern and southern hemispheres. All right ascension is measured along this circle.
Celestial Poles — North (NCP) and South (SCP), the projections of Earth's rotational axis. The sphere appears to rotate around these poles once per sidereal day (23h 56m 4s).
Ecliptic — The Sun's apparent annual path, tilted 23.44° to the equator (the obliquity, ε). The zodiac signs are 30° divisions of this circle.
Vernal Point (γ) — Where the ecliptic crosses the equator ascending northward. Zero point of both right ascension and ecliptic longitude.
Horizon — The great circle 90° from the observer's zenith. Divides visible from invisible sky.
Meridian — The great circle through zenith, nadir, and both celestial poles. Contains the MC (upper meridian) and IC (lower meridian).
Equatorial Coordinates
The topocentric system operates primarily in equatorial coordinates rather than ecliptic:
Right Ascension (RA, α) — Angular distance eastward along the equator from γ, measured in degrees (0°–360°) or hours (0h–24h).
Declination (δ) — Angular distance north (+) or south (−) of the equator, −90° to +90°.
RAMC (Right Ascension of the Midheaven) — The RA degree on the meridian at any given moment. Equivalent to local sidereal time expressed in degrees. Advances ~1° every 4 minutes of clock time.
Hour Angle (HA) — How far a body has traveled past the meridian, measured westward: HA = (RAMC − RA) mod 360°. HA = 0° at the MC; HA = 180° at the IC.
Fig. 1 — The Geocentric Horizon: celestial sphere with equator, ecliptic, horizon, and meridian
Fig. 2 — The Local Hemisphere: observer's visible dome with altitude-azimuth grid
II. The Topocentric Viewpoint
Classical positional astronomy places the observer at Earth's centre (the geocentric viewpoint). This is adequate for computing planetary longitudes, but for house division the distinction between geocentre and topocenter becomes critical.
Geocentre vs. Topocenter
The topocenter is the actual point on Earth's surface where the observer stands. Unlike the geocentre, the topocenter has a definite latitude and is displaced from the rotational axis by Earth's radius. This displacement creates measurable differences in the apparent positions of nearby bodies (the Moon especially) and — crucially for house division — defines a unique local horizon that does not pass through Earth's centre.
where π is the body's horizontal parallax and φ is the observer's latitude.
The Topocentric Axis
As Earth rotates, the topocenter traces a small circle around the polar axis. The topocentric axis is the line from the observer through Earth's centre, extended to the celestial sphere. This axis is tilted from the celestial polar axis by the complement of latitude (90° − φ), and rotates with the observer through the sidereal day.
Polich & Page recognized that house cusps should be computed from the topocenter, not the geocentre. The angular relationship between the topocentric axis and the celestial pole determines the pole of each house cusp — the latitude at which that cusp's degree would be exactly on the horizon.
Fig. 3 — The Topocenter: observer on Earth's surface with geocentric sphere and topocentric displacement
Fig. 4 — Rotation of the Topocenter: the daily circle traced by the observer around the polar axis
Fig. 5 — The Topocentric Axis: line from observer through geocentre, tilted by co-latitude
III. Diurnal Motion & Semi-Arcs
Every celestial body traces a diurnal circle — a small circle parallel to the equator — as Earth rotates. The portion of this circle above the horizon is the body's diurnal arc; the portion below is the nocturnal arc. Each half-arc, from horizon to meridian, is a semi-arc.
The Ascensional Cone
Geometrically, a planet's diurnal path traces the surface of a cone whose apex is at the celestial pole and whose half-angle equals the planet's co-declination (90° − |δ|). The horizon plane slices through this cone, and the intersection determines the rising and setting points.
Semi-Arc Formulae
Ascensional Difference: AD = arcsin(tan(δ) × tan(φ))Diurnal Semi-Arc: DSA = 90° + ADNocturnal Semi-Arc: NSA = 90° − AD
A planet with positive declination at a northern latitude has DSA > 90° (longer day), and vice versa. At the equator (φ = 0), all semi-arcs equal exactly 90°.
Meridian Distance
The meridian distance (MD) is the angular distance of a body from the nearer meridian (MC or IC), measured along the equator:
MD = min(HA, 360° − HA) adjusted to nearest meridian
MD ranges from 0° (on meridian) to the body's semi-arc (on horizon). The ratio MD/SA is the fundamental input to DMO.
Fig. 6 — The Ascensional Cone: a planet's diurnal circle traces a cone around the celestial pole
Fig. 7 — Ascensional Cone with House Cusps: intermediate cusps divide the semi-arc into unequal houses
IV. The Circumpolar Case
When a body's declination exceeds the co-latitude (|δ| > 90° − |φ|), it becomes circumpolar — it never sets (or never rises). Its diurnal circle lies entirely above (or entirely below) the horizon. The ascensional cone no longer intersects the horizon plane.
Upper & Lower Culmination
A circumpolar body still crosses the meridian twice per sidereal day: at upper culmination (highest altitude, HA = 0°) and lower culmination (lowest altitude, HA = 180°). The topocentric system handles circumpolar bodies by computing their DMO relative to these culmination points, using the full 360° diurnal circle as a single extended arc.
The Double Cone
For circumpolar stars, the diurnal path traces both an upper cone (above the pole, towards the zenith) and a lower cone (below the pole, grazing the horizon). The geometry is most dramatic at high latitudes, where many planets may be circumpolar for weeks at a time.
At latitude φ, any body with |δ| > 90° − |φ| is circumpolar. At φ = 60°N, the circumpolar zone begins at δ = +30°. At the Arctic Circle (φ = 66.5°), the Sun itself becomes circumpolar near the solstices.
Fig. 9 — The Circumpolar Cone: cone tangent to the horizon at the limit of visibility
Fig. 10 — Circumpolar at Lower Latitude: how the cone intersects the horizon at moderate latitudes
Fig. 11 — Expanded Circumpolar View: east and west hemisphere projections
Fig. 12 — Expanded Circumpolar with Houses: house boundaries in the circumpolar zone
V. The Horizon & House Division
The geocentric horizon is the great circle on the celestial sphere perpendicular to the observer's vertical (zenith-nadir axis). Combined with the meridian, it creates four natural sectors — the quadrants — which are the foundation of all house systems.
Quadrant Definition
The meridian (MC-IC axis) and horizon (ASC-DSC axis) divide the sphere into four quadrants. In the topocentric system these are identified by hour angle ranges:
Q4 (Houses 7, 8, 9): above horizon, west of meridian — HA 0°–90°
Q3 (Houses 4, 5, 6): below horizon, west — HA 91°–180°
Q2 (Houses 1, 2, 3): below horizon, east — HA 181°–270°
Q1 (Houses 10, 11, 12): above horizon, east — HA 271°–360°
Topocentric House Division
The Polich-Page system divides each quadrant into three houses using intermediate poles. The key insight: the pole of each house cusp varies linearly between 0° (at the MC/IC) and the observer's latitude φ (at the ASC/DSC). This produces cusps whose equatorial positions are defined by:
tan(polen) = tan(φ) × (n / 3)
where n = 1, 2, 3 counts the cusps from meridian toward horizon. The MC and IC have pole = 0°; the ASC and DSC have pole = φ.
This linear interpolation of poles is what gives the topocentric system its name and its distinctive character. Unlike Placidus (which uses time-based trisection of semi-arcs) or Regiomontanus (which projects from the equator), the topocentric system is defined by the geometry of the observer's position relative to the axis of rotation.
Fig. 13 — Geocentric Horizon: the horizon plane intersecting the celestial sphere
Fig. 14 — Topocentric Houses: the 12 cusps with intermediate poles shown as dashed lines
Fig. 15 — Topocentric Houses Unfolded: Mercator-like projection showing all house boundaries
Fig. 16 — Extended Topocenter: the topocentric axis extended beyond the celestial sphere
VI. Distance from Meridian (DMO)
The Distance from Meridian in Oblique Ascension (DMO) is the foundational measure of the topocentric system. It expresses every planet's position as a single number in the range 0°–90°, regardless of the planet's declination or the observer's latitude.
Definition
DMO = (MD / SA) × 90°
where MD is the meridian distance and SA is the relevant semi-arc (DSA if above horizon, NSA if below).
Interpretation
DMO = 0° — Planet is exactly on the meridian (MC or IC)
DMO = 90° — Planet is exactly on the horizon (ASC or DSC)
DMO = 30° — Planet is at the boundary of the 1st trisection from the meridian (i.e., on a house cusp)
DMO = 60° — Planet is at the 2nd trisection (the intermediate house cusp)
Two planets with the same DMO are mundanely parallel — they occupy the same proportional position in their respective quadrants, even if their ecliptic longitudes, RAs, and declinations are completely different. This is the core insight of the system: DMO creates a universal positional measure that transcends the particular geometry of each planet's diurnal arc.
Worked Example
Suppose the Sun has RA = 83°36', δ = +23°19', and the observer is at φ = 40°43' N with RAMC = 9°31':
The Sun is at DMO 59.66° in Q1 — deep in House 11, about two-thirds of the way from the MC to the ASC.
Fig. 17 — DMO Gauge: semicircular scale showing a planet's position from meridian (0°) to horizon (90°)
VII. Topocentric Poles
Each of the 12 house cusps in the topocentric system has a unique pole — the geographic latitude at which that cusp's ecliptic degree would rise exactly on the horizon. This pole determines how the cusp interacts with planets in the ascensional transit framework.
Pole Computation
The poles are interpolated linearly between the meridian (pole = 0°) and the horizon (pole = φ):
The pattern repeats symmetrically in Q3 and Q4. The MC and IC always have pole = 0°. The ASC and DSC always have pole = φ (the observer's latitude).
Planet Poles
A planet inherits a pole from its DMO position by the same interpolation. A planet at DMO = 45° (halfway between meridian and horizon) receives a pole of arctan(tan(φ) × 0.5). This is what distinguishes the topocentric system from Placidus: in Placidus, all computations use the observer's latitude φ directly; in the topocentric system, each planet has its own pole derived from its mundane position.
Comparison with Other Systems
Placidus: Uses φ uniformly for all bodies. Equivalent to topocentric at the angles only.
Regiomontanus: Projects from the equator via the celestial pole. Different pole structure.
Campanus: Projects from the prime vertical. No pole concept in the same sense.
Koch: Time-based, birthplace-specific. No general pole formula.
At very low latitudes (φ < 10°), topocentric and Placidus cusps converge. The systems diverge most dramatically above φ = 50°, where the pole variation across houses becomes large.
Fig. 18 — Pole Ladder: visualization of the 12 house poles from 0° to φ, showing linear interpolation
VIII. Oblique Ascension & Descension
The Oblique Ascension (OA) and Oblique Descension (OD) are the equatorial degrees that rise or set at the horizon simultaneously with a given celestial body, computed under the body's own topocentric pole. They are the fundamental values for computing aspects in the Polich & Page framework.
Formulae
Ascensional Difference: AD = arcsin(tan(δ) × tan(pole))Oblique Ascension: OA = RA − ADOblique Descension: OD = RA + AD
A planet above the horizon uses OA (computed at its rising point). A planet below uses OD (computed at its setting point). The choice depends on which semi-arc the planet occupies.
Why OA/OD Matter
Two planets whose OA (or OD) values differ by an exact harmonic angle (0°, 60°, 90°, 120°, 180°) are in equatorial aspect. This is fundamentally different from an ecliptical aspect (which compares zodiacal longitudes): an equatorial aspect reflects an actual geometric relationship on the celestial sphere, as seen from the observer's specific latitude and at their specific topocentric pole.
The power of OA/OD aspects is that they incorporate both the planet's position and the observer's latitude into the aspect geometry. Two charts cast for different latitudes will show different equatorial aspects for the same planets — which is astronomically correct and astrologically meaningful.
Fig. 19 — OA/OD Aspect Wheel: equatorial circle with aspect arcs highlighted between two planets
IX. Ascensional Transits (Aspects in Mundo)
The Polich & Page system recognizes five classes of aspect, each computed in a different coordinate space:
1. Equatorial (OA/OD) Aspects
Computed by comparing OA values (if both planets are above) or OD values (if both below), or cross-comparing OA/OD when planets are in different hemispheres. The aspect angle is the difference in the relevant OA/OD values.
Computed by comparing DMO values. Two planets whose DMO values differ by a harmonic fraction of 90° are in mundane aspect. Since DMO already normalizes for declination and latitude, mundane aspects are universal.
Two planets in adjacent quadrants whose DMO values sum to an exact harmonic angle are in symmetric aspect. This is the topocentric equivalent of antiscia: bodies equidistant from the same axis on opposite sides.
Two planets with equal DMO values (regardless of quadrant) are mundanely parallel. They occupy the same proportional position in their respective semi-arcs — a resonance of mundane position independent of ecliptic or equatorial coordinates.
5. Ingress Aspects
When a planet's DMO equals 30° or 60°, it sits exactly on a house cusp — an ingress moment with particular significance in the topocentric framework.
Orb Computation
Topocentrica uses a soft power law to compute orbs, tapering from a maximum at the first harmonic to near-zero at the tenth:
Orb(h) = 25′ × h−0.6
where h is the harmonic number. The master orb slider scales all orbs proportionally.
X. The Speculum
The speculum is the tabular display of every planet's positional data in the topocentric framework. Each column represents a specific computed quantity:
DMO — Distance from Meridian (0°–90°)
Q — Quadrant (Q1–Q4)
H — House number (1–12)
Pos — Above (▴) or Below (▾) the horizon
DSA — Diurnal semi-arc in degrees
Pole — Topocentric pole for this planet's position
Ecl.Lon — Ecliptic longitude (zodiacal position)
RA — Right ascension
Decl — Declination
OA — Oblique ascension under the planet's pole
OD — Oblique descension under the planet's pole
AD — Ascensional difference
Alt — Altitude above (+) or below (−) the horizon
Az — Azimuth (compass bearing from north)
Four Transposition Variants
Topocentrica computes the speculum under four different RAMC values simultaneously:
RADIX — The natal RAMC. Static natal positions.
TEMPORAL — The RAMC directed by solar arc. Shows how the natal chart has rotated over the native's lifetime.
LOCAL — The RAMC for the transit time at the natal location. The event chart at the birthplace.
FULL — The RAMC for the transit time at the transit location. The fully relocated event chart.
Each variant produces a different set of DMO values, poles, and aspects for the same planets. Cross-comparing aspects across variants reveals different layers of timing and location significance.
XI. Primary Directions
Primary directions are the oldest and most fundamental predictive technique in astrology. They model the rotation of the celestial sphere after birth, measuring how far the RAMC must advance (or retreat) before one body (promissor) reaches the mundane position of another (significator).
The Direction Arc
The arc of direction is the equatorial distance (in degrees) that the RAMC must rotate for the aspect to perfect. This arc is then converted to time using a key:
Age of event = Arc / Key rate
Arc-to-Time Keys
Naibod — 0°59'08" per year (mean daily solar motion). The most widely used key.
Ptolemy — 1°00'00" per year (the oldest key, from Tetrabiblos).
Cardan — Based on the actual solar motion at birth.
Synodic — Based on synodic periods.
Direction Systems
The direction arc can be computed under different house systems, each yielding slightly different results:
Topocentric — Uses the unique pole of each planet and cusp. The promissor is projected to the significator's pole, creating a direct equatorial comparison.
Placidian — Uses the Placidus Mundane Position (PMP), dividing the semi-arc proportionally. Historically dominant from the 17th century onward.
Regiomontanus — Projects through the equatorial poles. The medieval standard.
Campanus — Projects from the prime vertical. Rarely used for directions.
Topocentric Direction Formula
In the topocentric system, the direction arc for a promissor P aspecting a significator S is:
1. Compute the significator's position under its own pole: posS = RAS ± ADS(poleS)2. Compute the aspect point: asp = posS ± aspect_angle3. Project the promissor to the significator's pole: posP@S = RAP ± ADP(poleS)4. Direction arc = asp − posP@SThe critical distinction: in the topocentric system, the promissor is re-computed under the significator's pole, not its own pole. This creates a true geometric meeting at the significator's house position.
Fig. 20 — Direction Timeline: animated arc advancing from birth, showing a direction perfecting at a specific age
XII. Temporal Transposition
The temporal transposition is Polich & Page's technique for synthesizing primary directions with transit analysis. Instead of listing individual direction hits, the entire natal chart is rotated forward by the solar arc, producing a new set of house cusps, planet positions, and aspects for any moment in the native's life.
The Four RAMC Framework
At any moment in time, four different RAMC values are simultaneously meaningful:
RAMCradix = natal RAMC (fixed)RAMCtemporal = natal RAMC + solar arc (directed)RAMClocal = RAMC at natal location for the current momentRAMCfull = RAMC at current location for the current moment
Each RAMC generates a complete speculum: the natal planets under the rotated coordinate system. Aspects between the radix speculum and the temporal speculum reveal directed contacts; aspects between the radix and local specula reveal transit contacts at the birthplace; the full speculum shows relocated transit contacts.
Direct & Converse
The temporal RAMC can advance (direct) or retreat (converse). Direct transposition models the natural forward flow of the solar arc. Converse transposition reverses it — as if time ran backward from birth. Both yield valid and distinct aspect patterns.
XIII. Synastry in the Topocentric Frame
The topocentric system offers a uniquely powerful framework for synastry (chart comparison) because it operates in a coordinate space that inherently accounts for the observer's latitude.
Cross-Chart DMO Aspects
When two charts are compared, planets from Chart A can be evaluated by their DMO positions relative to Chart B's house framework. A planet from one chart at DMO 30° in Chart B's quadrant system sits exactly on one of B's house cusps — a powerful mundane contact.
Cross-Chart OA/OD Aspects
The OA and OD values from each chart can be cross-compared harmonically. Since OA/OD already incorporate each planet's pole (which depends on its mundane position in the reference chart), these aspects reflect a genuine angular relationship as seen from the specific latitude.
Mundane Overlays
Placing Chart A's planets in Chart B's topocentric house system (by computing their DMO under B's RAMC and latitude) reveals where A's energies fall in B's experiential framework. This is the mundane equivalent of placing one chart's planets in another's zodiacal houses.
XIV. Progressions in the Topocentric Frame
Progressed charts can be analyzed in the topocentric framework just as natal and transit charts are. The progressed planets' DMO values, poles, OA/OD, and aspects are computed against the natal speculum.
Progression Methods
Secondary (Day-for-a-Year): 1 sidereal day of planetary motion = 1 sidereal year of life. The most widely used progression.
Quinary (Year-for-a-Month): 1 sidereal year = ~1 sidereal month (~13× speed). Only Jupiter and Saturn produce meaningful events at this timescale.
Progressed DMO
The progressed chart produces its own RAMC, house cusps, and planet positions. Computing the DMO of each progressed planet against the natal RAMC reveals how far the progressed body has moved in the mundane frame. Cross-aspects between progressed and natal specula — in OA/OD, DMO, or ecliptical space — form the predictive core of the progressed topocentric analysis.
XV. Historical Context
The topocentric house system was developed by Wendel Polich and A.P. Nelson Page in Buenos Aires, Argentina, and published in 1964. Their work emerged from the vibrant South American astrological community of the mid-20th century, which was distinctive for its emphasis on mathematical rigour and empirical testing.
The Buenos Aires School
Polich and Page were part of a broader movement in Argentine astrology that sought to place house division and primary directions on a sound astronomical footing. Their system was designed from the ground up to satisfy three criteria:
Astronomical consistency — house cusps must correspond to physically meaningful positions on the celestial sphere.
Computational tractability — the system must be computable with the tools available (logarithmic tables and mechanical calculators in 1964).
Empirical accuracy — primary directions computed under the system must correlate with observed life events more reliably than competing systems.
Relationship to Other Systems
The topocentric system is often compared to Placidus because their cusps are numerically similar at most latitudes. However, the theoretical foundations are entirely different:
Placidus (17th century) divides each semi-arc into three equal time intervals. The cusps are found by asking: "At what RA will the ecliptic have completed 1/3 (or 2/3) of its semi-arc?"
Topocentric (1964) derives cusps from the geometry of the observer's position on Earth's surface. The cusps are found by linearly interpolating the topocentric pole from 0° to φ.
The two systems agree at the four angles (MC, IC, ASC, DSC) and diverge at intermediate cusps, with the divergence increasing at higher latitudes. Empirically, topocentric directions have been reported to produce tighter timing than Placidian directions, particularly for events timed to within a year.
Modern Implementation
With modern ephemeris libraries (Swiss Ephemeris) and computational power, the topocentric system can be computed to sub-arcsecond precision in milliseconds. This application implements the complete Polich-Page framework including all six direction systems, four arc-to-time keys, four RAMC transpositions, five aspect types, and the full progression hierarchy.
Topocentric Astrology — A Reference Treatise
Based on the work of Wendel Polich & A.P. Nelson Page (Buenos Aires, 1964) Interactive diagrams & guided tour
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