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Craft · lessons, benches & plates
Lesson 01 · The clock

1 The clock

Turn the recorded wall clock into Universal Time, then open the midnight plate on the correct Greenwich date.

Bench G1Stage 1 of 4 · Demonstration

Assessed lesson. Follow the source, retain your paper values, then complete the checks to unlock the next stage. Explore the clocks freely →

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 →

Demonstration

G1 · Royal Observatory, Greenwich

Follow the source and working. Advance one numbered line at a time.

0 of 7 lines checked0%
Frozen source given

Civil source clock

Clock diagram and date line
000306091215182108:0024-HOUR DIAL
08:00
13 Dec 2023
Civil source
08:00
13 Dec 2023
Summer time
0h
Standard zone
UTC+0
13 Dec 202300:0006:0012:0018:0000:0008:00 civil sourceKeep the calendar date attached to the clock.

The source givens and checked or revealed lines build this drawing. Unchecked future reference answers remain hidden.

Dial labels show whole minutes. The retained paper fields above preserve the original hours, minutes and seconds.

Permanent reduction formParts A–F

  1. Birth date, civil

    active line
    Frozen source given

    Civil source clock

    Clock diagram and date line
    000306091215182108:0024-HOUR DIAL
    08:00
    13 Dec 2023
    Civil source
    08:00
    13 Dec 2023
    Summer time
    0h
    Standard zone
    UTC+0
    13 Dec 202300:0006:0012:0018:0000:0008:00 civil sourceKeep the calendar date attached to the clock.

    The source givens and checked or revealed lines build this drawing. Unchecked future reference answers remain hidden.

    Dial labels show whole minutes. The retained paper fields above preserve the original hours, minutes and seconds.

    Why The recorded civil date is the starting datum because the Greenwich date can differ.

    Working

    Dec 13, 2023

    Your paper resultDec 13, 2023
    Reference answerDec 13, 2023
    Tolerance · exact

  2. Clock time, 24-hour

    waiting

  3. Summer time in force?

    waiting

    Rule if Y subtract 1h · older war time may be 2h · stated on the bench

  4. Standard time = A2 − A3

    waiting

  5. Zone offset from Greenwich

    waiting

    Rule West add · East subtract

  6. Universal Time = A4 + A5

    waiting

    Rule if 24h or more subtract 24h and move A7 forward a day · if below 0 add 24h and move A7 back

  7. UT date

    waiting

    Rule may differ from A1 · every plate row is read on this date

Moira Craft School

Blank permanent A–F reduction form

Part ATime

LineOperation and ruleWorkingResult
A1Birth date, civil
A2Clock time, 24-hour
A3Summer time in force?if Y subtract 1h · older war time may be 2h · stated on the bench
A4Standard time = A2 − A3
A5Zone offset from GreenwichWest add · East subtract
A6Universal Time = A4 + A5if 24h or more subtract 24h and move A7 forward a day · if below 0 add 24h and move A7 back
A7UT datemay differ from A1 · every plate row is read on this date

Part BSidereal time

LineOperation and ruleWorkingResult
B1Plate GST at midnight (0h UT) on the A7 dateread from the ephemeris row for A7
B2Interval since 0h = A6
B3Acceleration = B2 × 9.86 s per hourCheck: always under 4 minutes
B4Greenwich sidereal time at birth = B1 + B2 + B3carry at 60
B5Longitude in time = longitude × 4 min per degreeEast add · West subtract
B6Local sidereal time = B4 + B5if 24h or more subtract 24h
B7Southern hemisphere?if Y add 12h to B6 and normalise · this is the table entry

Part CAngles and cusps

LineOperation and ruleWorkingResult
C1Table rows bracketing B7: lower ST, upper STrows are 4 minutes apart
C2Fraction f = (B7 − lower) in seconds ÷ 240Check: always between 0 and 1
C3MC: lower, upper, difference, × f, + lowerthe same for every latitude
C4Latitude rows bracketing the birth: lower, upper; fraction gtable rows are 1° apart
C511 12 ASC 2 3 as columns: at the lower latitude, at the upper latitude, then by ga column that looks unlike its neighbours is the column with the mistake
C10Southern? Reverse every sign on C3 and C5degrees and minutes unchanged
C11Opposites: IC = MC + 180, DSC = ASC + 180, 5 6 8 9 = 11 12 2 3 + 180same degree and minute, opposite sign

Part DBodies

LineOperation and ruleWorkingResult
D:sunSun: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:moonMoon: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:mercuryMercury: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:venusVenus: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:marsMars: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:jupiterJupiter: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:saturnSaturn: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:uranusUranus: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:neptuneNeptune: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:plutoPluto: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts
D:trueNodeTrue Node: this midnight, next midnight, motion, × A6 ÷ 24, positionnegative motion is retrograde, write R · a negative travel subtracts

Part EFigure and aspects

LineOperation and ruleWorkingResult
E1Cusps on the wheel. ASC at the left, houses counterclockwise, C11 filled
E2Bodies into houses by comparing D5 with the cuspsnote any body within 1° of a cusp
E3Aspectarian: the five Ptolemaic aspects, applying or separating from motionorbs as on the free transits surface

Part FReceipt

LineOperation and ruleWorkingResult
FReceipt: paper, Moira, Δ, cause for every computed line

Part F · continuationPaper-to-Moira discrepancy account

Retain the paper value; record Moira, the signed delta, and one cause from the fixed vocabulary.
LinePaperMoiraΔCause / notes
A4
A5
A6
A7
B1
B2
B3
B4
B5
B6
B7
C1
C2
C3
C4
C5
C10
C11
D:sun
D:moon
D:mercury
D:venus
D:mars
D:jupiter
D:saturn
D:uranus
D:neptune
D:pluto
D:trueNode
E2
E3

Blank permanent A–F reduction form · tropical zodiac · Placidus houses