Book 0 · Hand calculation school

CraftBuild the sky.
Understand
every step.

Learn to calculate a natal chart by hand. Take it apart, do the reductions on paper, and watch the figure come together.

Begin lesson 01 Explore the clock

A paper form. A pencil. A reason for every value.

How this course works

Plate G1 · Greenwich07 / The figure

ASC: 20° ♐︎ 14′45.45″
MC: 23° ♎︎ 30′07.13″
Sun: 21° ♐︎ 01′57.27″
Moon: 25° ♐︎ 35′46.55″
Venus: 10° ♏︎ 07′15.58″
Saturn: 1° ♓︎ 48′27.09″

G1 frozen reference · tropical / Placidus · 4 of 11 bodies shown
Labels rounded to the nearest arcminute; geometry uses exact source longitudes.

Inspect the reference values

Historical Moira 6.4.1 · de441.bsp. This constructed source is separate from your paper work and the current engine.

Reference instant: 2023-12-13T08:00:00.000Z
Ascendant: 20° ♐︎ 14′45.45″ tropical longitude
Midheaven: 23° ♎︎ 30′07.13″ tropical longitude
Sun: 21° ♐︎ 01′57.27″ tropical longitude
Moon: 25° ♐︎ 35′46.55″ tropical longitude
Venus: 10° ♏︎ 07′15.58″ tropical longitude
Saturn: 1° ♓︎ 48′27.09″ tropical longitude

A reference preview. Select a layer to see what the calculation changes.

09Lessons in the craftFrom civil time to receipt

03Constructed practice benchesOne method, different skies

A–FA complete paper recordEvery reduction, traceable

The learning path

Nine reductions, one form

One chart. Nine discoveries. Explore a preview, then enter the lesson to build your own paper record.

Time

Structure

Bodies

Figure

Receipt

Learn

Lesson 07 · FigureMethod preview

ASC: 20° ♐︎ 14′45.45″
MC: 23° ♎︎ 30′07.13″
Sun: 21° ♐︎ 01′57.27″
Moon: 25° ♐︎ 35′46.55″
Venus: 10° ♏︎ 07′15.58″
Saturn: 1° ♓︎ 48′27.09″

G1 frozen reference · tropical / Placidus · 4 of 11 bodies shown
Labels rounded to the nearest arcminute; geometry uses exact source longitudes.

The figure

Place checked values onto the wheel. The Ascendant sets the orientation; cusps and bodies take their measured places.

Enter this lesson →

Preview selections do not check answers or complete lessons.

Explore · the first reduction

Same moment.
A different clock.

A clock correction can cross a date boundary. Step through it, watch it happen, and choose the right plate.

Denver, Colorado

Summer time 1h · standard zone UTC−7

19 Jul 2021 · 21:30 civil

Constructed example

Civil clock19 Jul 2021

Start with the civil record. Remove summer time once, then use the standard zone.

The paper reductionStep 1 of 4

1
Read the civil time
21:30
19 Jul 2021 · the time on the civil record
2
Remove summer time
—
Continue to reveal this reduction.
3
Standard-zone correction +7h
—
Continue to reveal this reduction.
4
Select the UT date
—
Reveal in step 4. The plate date can differ from the civil date.

Watch the date boundary

This is a free exploration. No course answers or completion are saved. Begin the assessed clock lesson →

Benches

One method, different skies.

Three constructed records make the corrections tangible. Open a source bench to inspect the printed givens.

Constructed bench	Civil record	What you will practise	Source
G1 Greenwich	08:0013 Dec 2023	The demonstration running example	Open bench →
D2 Denver	21:3019 Jul 2021	Summer time, a west zone and a UT date change	Open bench →
B3 Buenos Aires	14:205 Mar 2018	Independent practice and southern table reduction	Open bench →

How this course works

A source you can hold still

The three benches are constructed teaching cases. Their printed ephemeris and house tables are frozen, so the same source values are there each time you return. They are practice records, not a live chart calculation.

The arithmetic is yours

Follow a demonstration, complete the missing lines with guidance, then reduce a new case independently. Write each reduction on the permanent A–F form. The diagrams explain what a checked value changes.

A reason for every difference

Checking names the reference answer and tolerance. Keep your paper result alongside it, then account for any residual: rounding, a table interval, a date correction, or the method itself.

Your place stays on this device

Assessed lessons retain your active line, paper values and reviews in this browser. The free clock exploration saves no answers or completion. Course reset asks first and offers an exact undo.

The permanent form →Meet the Greenwich example →

Source instruments

Take the work to paper.

Keep every reduction on the permanent form, with the printed sources beside it.

Your course record 0 / 9 lessons complete

Last lesson / pass: Begin lesson 01 to establish your record on this device.
Lessons complete: 0 / 9
Queued remediation: Queue clear
Checkpoint scores: No checkpoint completed