Layer 5 — Charts and time techniques
A chart can freeze the sky at birth, compare it with another day, or rearrange its positions using a symbolic rule. The wheel may look similar in each case, so the most useful starting point is the question the calculation is meant to explore.
Natal chart
A natal chart records the bodies, signs, houses and angles for a birth instant and place. Natal means relating to birth. The chart is also called the radix, or root, because many later techniques use it as their reference.
If the natal Moon is at 15° Taurus, that remains the reference position when a later calculation moves to another year. Birth-time uncertainty still matters, especially for rapidly changing angles and houses. The root chart is only as specific as the information used to construct it.
Transit
A transit follows a body’s passage through a sign, position or relation to a reference point. It can describe a past, present or future sky. If natal Mars is at 10° Leo and the Sun reaches 10° Leo on a selected date, the transiting Sun is conjunct natal Mars.
The distinction to keep is fixed reference, moving sky. The birth position stays fixed while the transit instant advances. Daily, weekly and monthly forecasts often build interpretations around these changing relationships.
Secondary progression
A progression advances the chart using a symbolic time key. In secondary progression, one day after birth corresponds to one year of life. Age 30 therefore uses approximately the sky 30 days after birth, rather than the sky 30 years later.
The name distinguishes it from primary directions, a different timing construction. With the day-for-year key, the progressed Sun moves roughly a degree per year of life and the progressed Moon roughly a degree per month.
A progressed position is labelled by its symbolic time mapping. It should not be mistaken for an observed transit at the person’s current age.
Solar arc
An arc is an angular distance along a circle. Solar arc takes the distance travelled by the progressed Sun and adds it to every selected natal point.
If that distance is 30.2°, each directed position receives 30.2°, wrapping at 360°. The directed Moon therefore need not match the secondary-progressed Moon: one has received the Sun’s displacement, while the other follows the Moon’s own ephemeris position under the progression’s time key.
Some methods use the true progressed Sun and others a fixed mean rate. Naming the arc convention makes the resulting chart reproducible.
Tertiary and minor progression
Other progressions change the symbolic clock. Tertiary progression maps one day to one lunar month; minor progression maps one lunar month to one year. At the same age, these keys select different ephemeris instants from secondary progression.
Even “lunar month” needs a reference. A sidereal month follows the Moon back against the stars; a synodic month follows the return of its phase relative to the Sun. A precise progression specifies which interval its key uses.
Solar return
Instead of choosing an instant first, a solar return searches for one: the moment the Sun regains its natal longitude in the selected zodiac. A chart is then calculated for that moment, often for a yearly interpretation.
The crossing occurs around a birthday but can fall on a neighbouring civil date. Once the instant is found, the location still affects its houses. A return chart may use the birth location, current residence or another stated place.
Lunar return
A lunar return searches for the Moon’s return to its natal longitude, roughly every 27.3 days. A lunar phase return instead repeats the natal Sun–Moon angle, roughly every 29.5 days.
The difference is worth picturing: the Moon can return against the stellar background before it catches up with the Sun’s continuing motion enough to repeat the same phase. Position and phase give us different kinds of return.
Planetary return
The same search can be made for any planet. A Saturn return, for instance, occurs when Saturn regains its natal longitude, roughly every 29.5 years.
A retrograde loop can cross the same natal longitude several times in one return season. A search needs a time window and a rule for returning the first crossing or all crossings; “return” does not always name one unique event.
Synastry
Synastry compares two charts while keeping each person’s placements intact. Person A’s Venus can be compared with person B’s Mars, or one person’s planets can be read against the other’s houses. The compatibility interpretation is a separate set of rules applied to those comparisons.
A bi-wheel displays the two charts as concentric rings. Tri-wheels and quad-wheels display three and four. Adding rings changes the presentation, not the birth data belonging to each person.
Composite chart
A composite chart puts together a new set of positions from the midpoints of two charts. It is used to interpret a relationship as a combined entity.
For longitudes of 10° and 50°, the short-arc midpoint is 30°. For 350° and 10°, it is 0°, not the ordinary numerical average of 180°. The circle matters: the nearby points straddle zero.
Exactly opposite points have two equally short midpoint choices. Composite houses and angles also need a stated method. The combined positions generally do not describe one physical sky that existed at a single instant.
Davison chart
A Davison chart, named after Ronald Davison, combines the inputs rather than averaging each planetary longitude. It uses a midpoint birth instant and a geographic midpoint under a stated convention, then calculates the sky for those inputs.
This is the useful contrast with a composite: one combines positions; the other constructs a time and place. Both can have houses and angles, but they arrive at them through different rules.
Relocation chart
A relocation chart keeps the natal instant and changes the place. A different horizon changes the angles and houses while the geocentric planetary longitudes remain the same. This is the basis for exploring a chart in relation to moving or travel.
The familiar “same planets, different houses” description assumes geocentric positions. Topocentric positions can also shift when the observation location changes.
Horary
Horary takes its name from the hour: a chart is cast for the accepted moment of a question and interpreted in relation to it. Unlike a natal chart, its starting event is the question rather than a birth.
Schools differ about whether the moment is when a question is asked, received or understood by the astrologer. The accepted instant and location are therefore part of the method, not details supplied by the question’s wording alone.
Electional chart / Muhurta
An electional chart helps choose a time for an intended event, such as a wedding or launch. Electional refers to electing or choosing: candidate times are compared using stated astrological criteria.
Muhurta is the Jyotish tradition of selecting such times, with its own rules and panchang. It also names a traditional time unit. The shared aim of choosing a moment does not make every electional method identical.
Harmonic chart
A harmonic chart multiplies each longitude by a whole number and wraps the result into 0°–360°. In H4, a longitude of 100° becomes 40°. Two original positions 90° apart become conjunct because four times 90° is a full turn.
That collapse is the point of the construction: it makes a selected angle family appear as conjunctions. H5 and H9 use different multipliers and reveal different relationships. A Jyotish D9 chart also involves divisions, but its mapping and interpretation should be checked before equating it with a Western harmonic chart.
Antiscia
Reflect a position across the 0° Cancer–0° Capricorn axis and you find its antiscion; antiscia is the plural. The name evokes opposing shadows, associated with corresponding seasonal solar declinations.
The longitude reflection is (180° − longitude) mod 360°. For 10° Aries,
that gives 170°, or 20° Virgo. Contra-antiscia uses the point opposite
the antiscion. These are calculated reflections that can be compared with other placements.
Eclipse chart
A solar eclipse occurs when the Moon obscures the Sun for an observer. A lunar eclipse occurs when the Moon enters Earth’s shadow. Their relationship to the nodes explains why every new or full Moon is not an eclipse.
An eclipse chart is cast for a stated event within that eclipse. Greatest eclipse and local first contact are different instants. Finding whether an eclipse is visible from a city requires local geometry beyond the zodiac longitudes in a wheel.
Astrocartography (Astro Maps)
An astrocartography map carries a chart’s angular directions onto Earth. Its lines mark places where a planet was rising, setting, culminating or anti-culminating at the reference instant. A body in one of these directions is angular.
Related maps use different constructions. A paran relates bodies on angular directions at the same time; geodetic mapping assigns zodiac directions to geography under a separate rule. Interpretations about living near a line belong to the tradition applied after the map’s geometry is calculated.
Planetary stations
A station is a turning point in apparent longitude motion. An event search finds where longitude speed crosses zero and identifies whether direct or retrograde motion follows.
This gives a date and time to the retrograde cycle. A daily status flag only describes the sampled instant; the event search locates the transition itself.
Planetary nodes and apsides
The Moon is not the only body with nodes and apsides. A planet’s nodes mark where its orbit crosses a stated reference plane. Its apsides mark the nearest and farthest orbital points relative to the central body.
For Sun-centred orbits these ends are perihelion and aphelion; for Earth-centred orbits they are perigee and apogee. The centre, reference plane and mean or instantaneous orbital model are part of what identifies the calculated point.
Firdaria
Firdaria is a Persian time-lord system assigning successive portions of life to planetary rulers, with subperiods within them. A time-lord is a symbolic ruler assigned to a period, rather than a body remaining in one place for those years.
The commonly described cycle totals 75 years, beginning with the Sun for a day birth and the Moon for a night birth. Variants differ, particularly in the placement of nodal periods, so the sequence needs a named rule set.
Zodiacal Releasing
In Zodiacal Releasing, periods unfold from the sign of a selected lot, usually Spirit or Fortune. The Hellenistic technique advances through sign-ruled periods and nested subperiods, using conventional durations assigned to the signs.
“Releasing” describes that unfolding from a starting point. The periods are not the time a transiting planet takes to cross a sign. To see where the starting point comes from, we need one more kind of calculated chart position.
Lots / Parts
A lot, also called a Part, applies an angular relationship to an anchor.
The word carries the idea of an allotted share. One familiar example is the
Lot of Fortune: ASC + Moon − Sun in a common daytime convention, with the
Sun–Moon order reversed at night.
For ASC = 100°, Moon = 80° and Sun = 50°, daytime Fortune is 130°. Results are wrapped around the circle when needed.
Sect, the traditional day/night distinction here, depends on whether the Sun is above the horizon. It is not the same thing as the clock showing AM or PM.
Life time arcs
“Life time arcs” is a product label whose precise meaning needs checking. A fixed one-degree-per-year direction adds 40° at age 40. True solar arc instead uses the progressed Sun’s actual displacement, which need not be exactly 40°.
Before comparing outputs under this label, establish the rate, starting epoch, selected points and time convention. Recognising an ambiguous name is part of understanding the vocabulary: not every familiar-sounding label supplies a complete method.