March 2012 page 8
Mario Arnaldi

The Canterbury Pendant. Part 2: Relationships with the Libellus’ rule

This second part of the article investigates the Canterbury pendant, a 10th-century portable sundial. It compares its graphic layout with the Libellus de mensura horologii and the Roman cylinder dial of Este, exploring the use of two gnomons for different seasons and their relationship to hour curves.
Dials: Portable, Historical Dials, How Sundials Work, Mathematics of Dialling

March 2012 page 18
John Davis

A Portable Horologium

This article examines a medieval copper-based alloy device, found in Norfolk, which functioned as both a compass and a horologium. The fine engraving, including early Gothic lettering and 5° time subdivisions ("mileways"), suggests a 14th-century date and offers insights into medieval timekeeping and connections to local horology.
Dials: Portable, How Sundials Work, Historical Dials

March 2012 page 23
Mark Lennox-Boyd

La Meridiana

The author describes "La Meridiana," a house in Italy designed with a sundial as its stair tower. This indoor sundial uses projections and reflections onto north, west, and east walls, and the ceiling, to show time and date. The article highlights the mathematics, design, and extensive calibration process.
Construction Projects, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

March 2012 page 28
Dennis Cowan

Apparent Longitude Problems with some Scottish Sundials

This article investigates "longitude problems" on Scottish sundials from 1877-1913, including those by famous architects. The author discovers that the inscribed "longitude" is actually the time difference from Greenwich, making it more user-friendly for time telling and correcting previous assumptions about design errors.
How Sundials Work, Historical Dials

March 2012 page 36
Chris H. K. Williams

English Reformation and Protestant Scratch Dials of the 16th & 17th Centuries

This article examines how English church dials changed during the Reformation, contrasting the colorful, symbolic Catholic 360° dials with the minimalistic, functional Protestant 180° and 90° scratch dials. It uses dial data to inform historical debate on the pace and spread of Protestantism across England.
Dials: Mass Dials, Historical Dials, How Sundials Work

March 2012 page 42
Peter I. Drinkwater
Tony Wood
John Moir

Readers’ Letters

This section features letters from readers discussing various sundial topics. Peter Drinkwater discusses dial transmission and an Islamic scratch dial. Tony Wood offers insights into the progress of "scientific" sundials. John Moir describes "Suburban Reflections" from his front garden.
How Sundials Work, Historical Dials, The BSS and Members

March 2012 page 43
David Brown

The Scaphe Sundial at Hever Castle, Kent

This article details the author’s investigation into the enigmatic scaphe dial at Hever Castle, often called the "Roman" sundial. It discusses its historical background, previous examinations by Ward and Vaughan, and the author's measurements and analysis, concluding it is likely an unworkable dial despite its ancient appearance.
How Sundials Work, Historical Dials, Dials: Scaphe

June 2012 page 2
Allan A. Mills

Gaocheng Calendrical Observatory, China

This article details the historical Gaocheng Calendrical Observatory in China, focusing on its construction in 1276 AD by Guo Shoujing, its role in calendrical observations for the Yuan Dynasty, and its design principles for measuring solstices and equinoxes using a monumental gnomon. It also describes the 'shadow-definer' device used for accuracy and the methods for orientation and timekeeping.
Dials: Noon Lines, Historical Dials, How Sundials Work, Mathematics of Dialling

June 2012 page 20
Julien King

Sundials in GCSE Astronomy

This article discusses the role of sundials in the GCSE Astronomy qualification as an introduction to 'sun time' versus 'clock time', the Equation of Time, and longitude effects. It highlights two popular Controlled Assessment tasks: using a shadow stick to determine local noon and longitude, and comparing sundial time with local mean time to assess accuracy.
How Sundials Work, Equation of Time

June 2012 page 22
David Le Conte

The Brunson Universal Sun Compass

This article describes the Brunson Universal Sun Compass (Model 7637B), an elaborate US Army instrument developed in the 1950s. Its innovations included usability at all latitudes and a clockwork mechanism to counteract Earth's rotation, making it a valuable complement to magnetic/gyro-compasses for true azimuth determination in navigation and surveying.
Dials: Portable, How Sundials Work, Historical Dials

June 2012 page 42
Mike Cowham

Latitude Determination using an Equinoctial Ring Dial

This article describes Gabriel Stokes' innovative 1735 design for equinoctial ring dials, which incorporated a direct readout declination scale for latitude determination. By setting the suspension point to the correct solar declination for the day, travellers could directly read their geographical latitude, simplifying a process that traditionally required calculations.
Dials: Portable, How Sundials Work, Historical Dials

September 2012 page 2
Daniel Brown

A Standing Stone and its Possible Astronomical Alignment—Using seasonal shadow and light displays in the Neolithic

This article examines a 2-metre tall triangular monolith at Gardom’s Edge, Peak District, suggesting it was intentionally erected and astronomically aligned in the late Neolithic/early Bronze Age. It highlights how the stone's north-facing side would be illuminated during the summer, serving as a seasonal marker for ancient communities.
Dials: Unusual, Historical Dials, How Sundials Work, Sundial Design & Layout

September 2012 page 8
Michael Lowne
John Davis

The Stereographic Projection and Quadrant by Henry Sutton

This article explores Henry Sutton's quadrant, which utilises a stereographic projection of the sky onto the equatorial plane, initially conceived by Thomas Harvey. It details the instrument's design, including scales for time-telling and other astronomical problems, and provides instructions for its use, such as finding the time at night using stars.
How Sundials Work, Mathematics of Dialling, Historical Dials

September 2012 page 20
Mike Cowham

The Planispheric Nocturnal

This article describes the planispheric nocturnal, an instrument for telling time at night by aligning a rotating star chart with actual stars. It functions as an alternative to a traditional nocturnal and can be found on the reverse of some quadrants, offering timekeeping to within 15 minutes without requiring Equation of Time correction.
Dialling Tools, How Sundials Work, Dials: Nocturnals

September 2012 page 21
John Davis

The Clock and the Sundial

This brief piece features an early Netherlandish image, dating from the late 16th century, which combines a lantern clock and a sundial. It serves as a visual reminder that clocks merely indicate time, whereas sundials actively find time, subtly suggesting the clock's potential inaccuracy compared to the sundial.
Historical Dials, How Sundials Work

September 2012 page 41
Sara Shafiei
Ben Cowd

Mosque of the Sun II: Crown of Doha

This article presents an architectural study for a solar dome, "Mosque of the Sun II: Crown of Doha" designed to align with the sun for prayer times and celestial events. It uses digital modeling and 3D printing, with the dome's solar orientation differing from the Mecca-aligned prayer room, allowing light to create a clock/calendar on the floor.
Dials: Unusual, How Sundials Work, Sundial Design & Layout, Construction Projects

December 2012 page 20
Michael Lowne

Window Reflections

This article investigates the cross-shaped reflections from double-glazed windows, attributing them to the concavity of the glass panes. Optical analysis reveals radial slope profiles and contour maps, showing a central depression. The phenomenon is likely caused by a partial vacuum inside the units, bending the glass inwards, forming distinct V-shaped patterns on narrow windows.
Dials: Reflected, How Sundials Work

December 2012 page 22
Jackie Jones

North-Facing Mass Dials

This article discusses mass dials on the north side of churches, specifically at Litlington and Firle in East Sussex. While a south-facing dial at Litlington is an early scientific dial, two north-facing mass dials, initially puzzling, were observed to work perfectly for evening use in summer, suggesting intentional placement.
Dials: Mass Dials, Dials: Vertical, Historical Dials, How Sundials Work

December 2012 page 28
Sue Manston

BSS Newbury Meeting, 22 September 2012

This report summarises the BSS Newbury Meeting, covering presentations on John Davis's "Mystery Welsh Sundial," Doug Bateman's "Romeo & Juliet Sundial," Kevin Karney's "Getting the Numbers Right" on dial layouts, and John Foad's project to put BSS Register dials online.
How Sundials Work, Mathematics of Dialling, Sundial Design & Layout, The BSS and Members

December 2012 page 41
John Davis

Helical Sundials

The article discusses helical sundials, particularly one made by Aylmer Astbury. These are a form of equatorial dial, with a brass strip helix marking hours via small holes or a terminator shadow. They can be adjusted for longitude and Equation of Time by rotating the helix on its axis, as explained in a 1992 Bulletin article.
Dials: Equatorial, Dials: Unusual, How Sundials Work, Sundial Design & Layout

March 2011 page 6
Jérôme Bonnin

Symbolic Meanings of Sundials in Antiquity. Introduced by an Explanation of Ancient Timekeepers

This article explores the symbolic meanings of sundials in antiquity, drawing on literary and epigraphical evidence from the Greco-Roman world. It also introduces ancient timekeepers, including clepsydra and various types of horologia, and discusses the differences between Greek and Roman dials.
How Sundials Work, Historical Dials

March 2011 page 18
Jos Kint
Stan Ulens

Two Methods to Find the Eccentricity of the Earth’s Orbit from Measurements with a Sundial. Part 2—Observations and Calculations of e

This second part details observations and calculations to determine Earth's orbit eccentricity using a sundial. It applies Ptolemy's geometrical model and an algebraic approach based on the Equation of Time, finding surprisingly accurate results despite the sensitivity of initial conditions.
Equation of Time, How Sundials Work, Mathematics of Dialling

March 2011 page 34
Mike Cowham

A Sun Simulator for Moyse’s Hall Museum, Bury St Edmunds

This article describes the creation of a motorised sun simulator for a museum exhibition, designed to demonstrate how sundials work by speeding up daylight duration. It features three lights for different seasons and allows visitors to test card sundial kits.
Construction Projects, Dialling Tools, How Sundials Work

March 2011 page 43
John Moir

Shadowy Secrets. Part 6—The Limits of Latitude in Sundial Design

This article explores how artistic objectives and geographical latitude impose limits on sundial design. It provides examples like an 'Arrow of Time' dial and an 'Apple Tree' dial, illustrating how proportions and realism are affected by latitude, and introduces a 'geographically modified' armillary octahedron.
How Sundials Work, Sundial Design & Layout

June 2011 page 2
Allan A. Mills

The Rainbow as a Solar Timekeeper

This article explores the rainbow as an alternative solar timekeeping phenomenon, discussing its complex optical properties, formation of primary and secondary bows, and the dispersion of light into colours. It also describes a rainbow dial instrument for time determination.
Dials: Unusual, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

June 2011 page 36
Peter I. Drinkwater

The Ecclesiastical ‘Scratch Dial’ as a Serious Timekeeper

This article argues that medieval 'scratch dials' were serious timekeepers, not just symbolic. It describes their basic form, historical context of temporal hours, and connections to early Church observances and Islamic prayer times, asserting their utility at high latitudes.
Dials: Mass Dials, Historical Dials, How Sundials Work, Mathematics of Dialling

September 2011 page 10
Malcolm Barnfield

The Sundial Goes To War. Part 2

This is the second part of an article exploring the use of sundials and solar compasses in military contexts. It describes instruments like the Marean-Kielhorn Director, Howard Sun Compass, Evans-Lombe, Richards, and Micklethwait sun compasses used by Allied forces. It also details German sun compasses, particularly the C. Plath device used by Rommel's Afrika Korps, and the astrocompass, discussing their applications and limitations in wartime navigation.
Dials: Portable, How Sundials Work, Historical Dials

September 2011 page 16
Allan A. Mills

Ancient Egyptian Sundials

This article reviews ancient Egyptian timekeeping, debunking obelisks as gnomons and a Cairo Museum artifact as a sundial. It focuses on the ‘sloping’ or ‘inclined plane’ portable, seasonal-hour altitude dials, such as the Qantara dial, and earlier L-shaped 'shadow sticks' from the New Kingdom, discussing their construction, use, and the challenges in interpreting their time-telling functions.
Dials: Portable, Dials: Unusual, Historical Dials, How Sundials Work

September 2011 page 20
Chris H. K. Williams

English Mass & Scratch Dials c.1250–c.1650 Combining statistical and religious evidence

This article examines the evolution of English mass and scratch dials between c.1250 and c.1650, linking changes in their appearance to the Reformation. It argues that understanding these dials requires interpreting them within their contemporaneous religious and iconographic contexts, highlighting the dramatic shift from elaborate Catholic church decoration to Protestant minimalism, which significantly impacted dial design around 1500.
Dials: Mass Dials, Historical Dials, How Sundials Work

September 2011 page 27
Christopher Daniel

Nature Club of Pakistan

This report highlights a successful gnomonical science studies programme by the Nature Club of Pakistan in Lahore and Faisalabad schools with support from the BSS.
Dials: Horizontal, Dials: Equatorial, How Sundials Work, DIY Sundial Projects, The BSS and Members

September 2011 page 34
William Watson
Michael Lowne

Simple Instrument for Finding a Meridian Line

William Watson describes a new instrument for finding a meridian line to aid in sundial making, using two tubes aligned with Polaris and Capella. Michael Lowne comments on the necessity of accounting for Polaris's displacement from the true pole and the stars' right ascension difference for correct alignment, noting potential inaccuracies in Watson's original design and challenges in its use.
How Sundials Work, Mathematics of Dialling, Dialling Tools

September 2011 page 45
Michael Lowne
John Davis

A Horizontal Quadrant of 1658 by Henry Sutton. Pt. 2

This second part examines the scales and uses of a 1658 horizontal quadrant by Henry Sutton, collaborating with John Collins. It details the matched sine and tangent scales for astronomical calculations, star positions for night-time finding, calendar tables for moon age and high water, and shadow/quadrat scales for measuring building heights. It also provides biographies of Collins, Dary, and Sutton, highlighting their roles in 17th-century London's mathematical community.
How Sundials Work, Mathematics of Dialling, Historical Dials

December 2011 page 42
Frank King

Mind the Gap – Sundials and Leap Years

This article addresses the difficulties of accommodating leap years on sundial calendars, particularly when showing the equation of time or solar declination. It explains how to design scales for precise readings despite the difference between tropical and civil years, and discusses the historical debate around which day (24th or 29th February) is the "extra" leap day. Practical design solutions are proposed.
Equation of Time, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

March 2010 page 48
Tony Belk

Photographer’s Dial—Part 2

An extension of a previous article on a photographer's sundial. This part adds a scale to indicate the sun's altitude and provides a new design for use at 54° N, which, together with the original 51.5° N dial, covers all of England.
DIY Sundial Projects, How Sundials Work, Sundial Design & Layout

June 2010 page 18
Michael Lowne
John Davis

The Horizontal Quadrant – Part 1, Introduction and Instruments

This paper introduces the horizontal quadrant, a less common but useful altitude sundial type, sharing its basic stereographic projection with the double horizontal dial. It discusses its history, including European precursors like Hartmann's compast and Apian's triens, and English developments by Delamain and Oughtred. The article describes the general form and known examples, detailing how it uses the sun's altitude to tell time.
How Sundials Work, Mathematics of Dialling, Historical Dials

September 2010 page 10
Michael Lowne
John Davis

The Horizontal Quadrant. Pt. 2: Use, and the Inverted Quadrant

This article details the use of horizontal quadrants for time-finding and surveying, including a rare 'inverted' variant. It describes how to determine time from solar altitude and declination, and from stars at night, discussing the historical accuracy and limitations of these instruments.
How Sundials Work, Mathematics of Dialling, Historical Dials, Dials: Nocturnals

September 2010 page 16
John Moir

Shadowy Secrets. Pt. 5: Shadows in the Mind

This article explores the psychological aspects of shadow perception, discussing how the mind interprets shadows, optical illusions, and perspective effects, as demonstrated by experiments with babies and examples of manipulated shadows or moon terminators.
How Sundials Work

September 2010 page 32
Stan Ulens
Jos Kint

Two Methods to Find the Eccentricity of the Earth’s Orbit From Measurements with a Sundial. Pt. 1: Theoretical Considerations

This article presents two theoretical methods to calculate the Earth's orbital eccentricity using sundial measurements. The first method uses the Ptolemaic geocentric model and season lengths; the second derives eccentricity from the Equation of Time by separating the part due to obliquity from the total.
Equation of Time, How Sundials Work, Mathematics of Dialling

September 2010 page 35
Maurice Kenn
Roger Bowling

Readers’ Letters

This section contains two letters: Maurice J. Kenn congratulates Michael Maltin on his 'Novel Meridian Finder' and discusses the dipleidoscope; Roger Bowling queries if anyone has seen Haidinger’s brushes and the perception of polarised light.
How Sundials Work, Dialling Tools

December 2010 page 7
Frans W. Maes
Allan A. Mills
Michael Lowne

Readers’ Letters

This section includes letters from readers. Frans Maes describes a multi-faceted obelisk sundial in Schwäbisch Gmünd, Germany, similar to one previously discussed. Allan Mills and Michael Lowne provide detailed explanations and practical advice on how to observe the optical phenomenon known as 'Haidinger’s brush,' which appears due to polarized light in the blue sky.
Dials: Multi Faced, How Sundials Work

December 2010 page 9
Frank King

A New Babylonian and Italian Hours Sundial for Selwyn College, Cambridge. Pt. 2. Numerical Insights

This article is the second part of a series detailing the Selwyn College sundial, focusing on its numerical properties. It explains the criss-cross pattern of Babylonian and Italian hour-lines, their relationship with French hours, and the concept of 'extra daylight.' It also provides methods for setting out these hour-lines.
Dials: Unusual, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

December 2010 page 17
John Ward
Margaret Folkard
Ron Blum

The Benares (India) Sundial in Three Dimensions

This article discusses the Benares Sundial, one of five equatorial sundial observatories built in India by astronomer prince Sawai Jai Singh II in the 18th century to rectify astrological errors. The authors also describe their work with stereoscopic images and an autocyclostereoscope for viewing 3D images without special glasses, including a 1902 stereograph of the Benares sundial.
Dials: Equatorial, How Sundials Work, Historical Dials

December 2010 page 33
David Scott

The Perception of Time in Anglo-Saxon England

This article explores how time was perceived and reckoned in Anglo-Saxon England, drawing on surviving sundials and manuscripts. It covers heathen time-reckoning based on natural cycles, the introduction of systematic time-reckoning by Christian missions (including the Julian calendar, horologia, and Canonical Hours), and later monastic and village time-marking methods like shadow-length horologia and mass-dials, which evolved until the advent of mechanical clocks.
Dials: Mass Dials, Historical Dials, How Sundials Work

December 2010 page 42
Chris H. K. Williams

The Evolution of English Mass & Scratch Dials c. 1250-1650. Pt. 2. Age Ranking Dials by Type

This second part of an article series establishes a method for age-ranking English mass and scratch dials (360°, 180°, and 90° types) from c.1250–c.1650. It uses cross-sectional analysis to demonstrate that 360° dials are the oldest, with their use ending around 1500 in favour of 180° and 90° types. The article also accounts for dial loss and regional adoption variations.
How Sundials Work, Historical Dials, Dials: Mass Dials

March 2009 page 2
Allan A. Mills

A North-facing Polarization Sundial of Varying Hue

This article explores alternative methods for measuring the sun's position, specifically focusing on a north-facing polarization sundial. It delves into the principles of polarized light from the sky, its application in sundial design using materials like 'Sellotape', and the construction of an experimental translucent equatorial dial that produces varying interference colours throughout the day.
Construction Projects, DIY Sundial Projects, Dials: Polar, How Sundials Work

March 2009 page 13
Maurice Kenn

Reader’s Letter

Maurice Kenn shares observations from Brisbane, Australia, contrasting the reliability of his universal equatorial 'coffee-time' sundial and heliochronometer with his UK radio-controlled clock. He notes the significant variation in local apparent noon relative to Eastern Standard Time in Brisbane.
Dials: Equatorial, Dials: Heliochronometer, How Sundials Work

March 2009 page 14
Allan A. Mills

An Electronic Polarization Sundial and Photometer

This article describes an electronic polarization sundial and sky photometer designed to measure the intensity and polarization of skylight. It uses a rotatable polar and a selenium photovoltaic cell to detect the solar meridian to within ±8 minutes of time and quantitatively assess the percentage of linear polarization in light from a selected area of the sky.
Dials: Polar, How Sundials Work, Construction Projects

March 2009 page 37
Mike Shaw

Book Review

This review covers "A Study of Altitude Dials" by Mike Cowham (BSS Monograph No 4). It praises the monograph's comprehensive overview of altitude dials, including their construction, accuracy, and various types like pillar, chalice, and quadrant dials. The book also provides detailed construction guides, diagrams, and a CD-Rom with templates for readers to make their own dials.
How Sundials Work, Book Reviews, Sundial Design & Layout, DIY Sundial Projects

June 2009 page 10
Tony Belk

Errors in dials at the wrong latitude

An analysis of the time-telling errors that occur when a horizontal or vertical non-declining sundial is used at a latitude different from its design latitude. The article provides tables and graphs illustrating the magnitude of these errors at different times of day and for different solar declinations.
Dials: Horizontal, Dials: Vertical, How Sundials Work, Mathematics of Dialling

June 2009 page 41
Mike Cowham

Altitude dials for tropical regions

Explores the design of fixed-latitude altitude dials for use in tropical regions, specifically The Gambia (13.5° N). The article presents computer-generated plots for various types, including the horary quadrant and vertical plate dial, highlighting the unique behaviour of the hour lines as the sun passes overhead.
Dials: Portable, How Sundials Work, Sundial Design & Layout

September 2009 page 10
Michael J. Harley

Prehistoric sundials in Ireland

Explores potential prehistoric sundials within the megalithic passage tombs of Brú na Bóinne in Ireland, including Newgrange, Dowth, and Knowth. The article examines specific stone carvings, such as the 'Stone of the Seven Suns' and Kerbstones K7 and K15 at Knowth, discussing theories that they may be sundials or calendars.
Dials: Unusual, Historical Dials, How Sundials Work

September 2009 page 20
Michael Lowne

Reader’s letter

A letter responding to a previous article on Kircher’s 'Organum Heliocausticum'. The author argues that the instrument as depicted could not work because the focal length of the spherical lens is drawn incorrectly.
Dials: Unusual, How Sundials Work

September 2009 page 46
Chris Lusby Taylor

The housewife’s trick

Re-evaluates A.P. Herbert's suggestion of turning a horizontal sundial to make it agree with mean time. While previously dismissed as inaccurate, this article presents a theoretical analysis and a practical implementation showing that, for UK latitudes, the 'trick' can keep the dial accurate to within a minute for most of the year.
Dials: Horizontal, Equation of Time, How Sundials Work, Mathematics of Dialling

December 2009 page 5
Kevin Karney
Colin Davis

Reader’s letter

The first letter describes an innovative focusing sphere lens made of lucite and copper sulphate, designed for use in a sundial. The second letter confirms that Samuel Turner, a diallist, was also the sculptor of his own tombstone which features a direct west dial.
Dials: Unusual, How Sundials Work, Historical Dials

December 2009 page 10
Allan A. Mills

A tribute to Robert Hooke

This article celebrates the genius of Robert Hooke, highlighting his key scientific contributions. It covers Hooke's Law and its application to timekeeping, his work on a universal joint for delineating sundials, and his pioneering (though unpublished) insights into the catenary arch. It proposes a sculptural memorial to Hooke.
How Sundials Work, Sundial Design & Layout, Historical Dials

March 2008 page 14
Mike Cowham

Finding the Sun’s Position in the Zodiac

This article explains how to use Solar Course diagrams found on historical instruments, such as an Edmund Culpeper universal equinoctial ring dial and Italian quadrants, to determine the sun's position in the Zodiac. It details calculation methods, including adjustments for Old Style and New Style calendars, and notes rare instances of early Gregorian calendar pre-emption.
Dialling Tools, Historical Dials, How Sundials Work, Mathematics of Dialling

March 2008 page 26
Fiona Vincent

Astrological Symbols on Sundials

Discusses the historical use and modern relevance of astrological symbols on sundials to indicate dates like solstices and equinoxes, despite astronomical shifts like precession. It examines symbols for Zodiacal signs and those used on lunar volvelles, such as sextile, square, and trine, explaining their relation to moon phases and elongation.
Historical Dials, How Sundials Work, Sundial Design & Layout

March 2008 page 31
Tony Ashmore

Astrolabes: Pt 4 Universal Astrolabes

This fourth part of a series describes universal astrolabes, focusing on the Saphea, Rojas, and De la Hire projections. These instruments, developed from the 11th to 17th centuries, could be used at all latitudes, offering flexibility for astronomical and timekeeping purposes, despite the increasing complexity of their design.
Dials: Astrolabe, Historical Dials, How Sundials Work, Mathematics of Dialling

March 2008 page 40
Tim Hunkin

Sundials

Reproduces Tim Hunkin's 'Rudiments of Wisdom' cartoon strip on sundials from the Observer newspaper. It offers a general introduction to sundials but points out historical inaccuracies, such as the Roman, not Egyptian, use of obelisks as gnomons and details regarding Charles Wheatstone's polarised light sundial.
Dials: Reflected, Historical Dials, How Sundials Work

September 2008 page 112
John Moir

Shadowy Secrets, Part 4: The Art and Artifice of the Gnomon

This article explores the artistic and innovative designs of gnomons, moving beyond simple functional brackets to decorative, contextual, or 'shadow-play' designs. It provides examples of gnomons incorporating visual puns, personal initials, and a novel method for designing a gnomon to cast a true profile shadow on a specific date and time.
DIY Sundial Projects, How Sundials Work, Sundial Design & Layout

September 2008 page 130
Tony Ashmore

Astrolabes, Part 5 - Other astrolabe related instruments

This part of the Astrolabes series covers instruments related to, but distinct from, planispheric astrolabes. It discusses the rare spherical and linear astrolabes, monumental and domestic astrolabe clocks, mariner's astrolabes (not true astrolabes), and various types of quadrants, including horary and astrolabe quadrants, detailing their history and use.
Dials: Astrolabe, Dialling Tools, Historical Dials, How Sundials Work

December 2008 page 154
Mike Cowham

The Universal East and West Polar Dial

This article describes a portable universal East and West polar dial that is self-aligning and does not require a compass. It details its design, operation, and identifies limitations such as a two-hour gap around noon. It also explores improvements through hinged flaps and cylindrical designs, and relates it to other dial types like the double crescent dial.
Dials: Polar, Dials: Portable, How Sundials Work, Sundial Design & Layout

December 2008 page 160
Ken Head

Analemmatic Dials—Design Data

This article provides a summary of data and equations needed to delineate and set out analemmatic sundials. It discusses the projection of an equatorial dial onto a horizontal surface, using a vertical gnomon whose position varies with the sun's declination, and the calculation of sunrise and sunset markers using Lambert circles and Bailey Points.
Dials: Analemmatic, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

December 2008 page 169
Tony Belk

Diallist’s Alphabet

A light-hearted alphabetical list of terms and concepts related to sundials and dialling. It covers various aspects from Apparent time to Zodiac, including types of dials, mathematical concepts, and references to the British Sundial Society and its members.
How Sundials Work, The BSS and Members

December 2008 page 170
Tony Belk

Polar Dials at any Declination

This article presents a method for designing polar sundials for any latitude and declination using four simple formulae. It explains that polar dials have a style parallel with the dial plane and parallel hour lines, and describes how to determine the angle of the equinox line and the sub-style hour angle.
Dials: Polar, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

March 2007 page 9
Chris Lusby Taylor
Tony Ashmore
Allan A. Mills

Readers’ letters

This section contains correspondence from readers. Chris Lusby Taylor discusses the use of Hooke’s joint for delineating declining and reclining dials, while Allan Mills replies regarding an error in a previous paper. Tony Ashmore suggests an interpretation for the 'Egyptian Face' design on a sundial pillar at Lord Tennyson's home, attributing it to Ptolemy.
Dials: Unusual, How Sundials Work, Mathematics of Dialling

March 2007 page 10
John Wall

Earth’s rotation

John Wall explores the hypothetical consequences if the Earth's rotation on its axis were reversed. He details impacts on sunrise/sunset directions, calendar year length, solar day duration, star progression, International Date Line adjustments, and time zones. The article also touches upon how sundials would still function with reversed numerals.
How Sundials Work

March 2007 page 24
Chris Lusby Taylor

A universal Italian and Babylonian hour accessory

This paper introduces a simple accessory, a three-quarters CD, that can be used with existing horizontal sundials to signify Italian and Babylonian hours. It explains how these hour systems differ from conventional timekeeping and how the accessory allows us to read these hours, using the shadow of the CD.
Dials: Horizontal, How Sundials Work, Dialling Tools, DIY Sundial Projects

March 2007 page 33
Stefano Barbolini
Guido Dresti
Frank King
Rosario Mosello

The sundial in La Specola Museum, Florence

This paper describes the pinhole sundial in the Grand-Ducal Astronomical Observatory (La Specola) in Florence. It covers the observatory's history, the sundial's design as a string-gnomon meridian line, its restoration in 2005, and a comparison of measured zodiac point positions with calculated values. It highlights the instrument's historical importance for astronomical studies and calendar reform.
Dials: Noon Lines, Historical Dials, How Sundials Work, Restoration projects

March 2007 page 46
Ken Head

Orientation of St Mary’s Church, Stoke D’Abernon, Surrey

This article re-examines the orientation of St Mary’s Church, Stoke D’Abernon, considering the 7th-century Saxon church and its 13th-century chancel misalignment. It calculates sunrise azimuths for the Feast of the Annunciation, accounting for horizon elevation and atmospheric refraction, to explore the hypothesis that church alignment relates to sunrise on the patron saint's day.
Historical Dials, How Sundials Work

June 2007 page 78
Ken Head

Sunrise and Sunset Hours on a Garden Analemmatic Dial

This article discusses the determination of sunrise and sunset directions and times using garden analemmatic sundials. It explains the dial's principles, the Bailey points for seasonal markers, and evaluates the accuracy of these markers, noting discrepancies and suggesting practical applications for garden dials despite minor errors.
Dials: Analemmatic, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

June 2007 page 82
Fred Sawyer
Michael Faraday
Tony Wood

Readers’ Letters

This section contains reader correspondence. Fred Sawyer corrects an article on dual sundials, attributing the self-setting property to Vaulezard (1640) rather than Tuttell (1698). Mike Faraday asks for a website to track the terminator for sunrise times. Tony Wood clarifies the location and movement of the Ross-on-Wye pillar dial.
Dials: Analemmatic, How Sundials Work, Historical Dials

June 2007 page 86
Chris Lusby Taylor

BSS Annual Conference—Fitzwilliam College, Cambridge

This report summarises the 2007 British Sundial Society Annual Conference in Cambridge. It highlights talks on calendar history, the Equation of Time, analemmatic sundials, astrolabes, and beehive sundialling. It also covers walking tours of Cambridge dials, including Pembroke and Queens' Colleges, and the Andrew Somerville Memorial Lecture on calendar accuracy.
Dials: Astrolabe, Historical Dials, How Sundials Work, The BSS and Members

June 2007 page 91
Tony Ashmore

Astrolabes—Part 1, Introduction

This is the first part of a series introducing astrolabes, describing them as two-dimensional analogue computers for solving spherical trigonometric problems and finding time. It covers their history from Greek origins through Arab development to European decline, and explains the principles of their design including the rete and engraved plates for different latitudes.
Dials: Astrolabe, Historical Dials, How Sundials Work, Mathematics of Dialling

June 2007 page 95
Fiona Vincent

Solar and Lunar Data 2007

This entry provides a table of solar and lunar data for 2007, including daily declination and transit times, as well as moon phase information for June, July, and August.
How Sundials Work

September 2007 page 102
Allan A. Mills

Hour Angle, Velocity and Acceleration of the Shadow Moving over a Sundial

This paper applies Hooke's joint equation of motion to sundials to calculate the hour angle, angular velocity, and acceleration of the shadow. It provides formulas and graphs for a direct south vertical dial at 52° N latitude, showing how these parameters vary throughout the day, with angular velocity minima at noon/midnight and maxima at 6 am/pm.
How Sundials Work, Mathematics of Dialling

September 2007 page 107
Tony Ashmore

Astrolabes: Pt. 2. European Astrolabes

This second part details the characteristics and scales of European astrolabes. It covers the use of Latin script and numerals, simple throne designs (with some Flemish exceptions), and variable rete strapwork. The article also explains the zodiac/calendar scales, shadow squares for surveying, and three methods for determining unequal (planetary) hours found on these instruments.
Dials: Astrolabe, Historical Dials, How Sundials Work

September 2007 page 114
Frank Evans

Strange Longitude

This article investigates a peculiar Pl. Long. inscription on the 1845 Hawkshead Grammar School sundial. Through extensive correspondence, Pl Long was identified as The Plane's Longitude referring to the hour angle in angular measure when the sun is directly over the style, rather than a geographical longitude.
Dials: Vertical, How Sundials Work, Sundial Design & Layout

September 2007 page 128
Michael Lowne
John Davis

Lines of Declination and Two Seventeenth Century Dials

This article explores declination lines on sundials as conic sections and details methods for their delineation. It examines two 17th-century horizontal dials by Isaac Symmes (Science Museum, Oxford), noting errors in their declination lines and the presence of seasonal hours and lunar volvelles. A new graphical method for drawing declination lines is also presented.
Historical Dials, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

September 2007 page 134
Fiona Vincent

Solar and Lunar Data

This entry provides a table of solar and lunar data for September, October, and November. It includes daily values for declination and transit times, as well as lunar quarter and new/full moon phases. This data is useful for sundial calibration and understanding celestial movements.
Equation of Time, How Sundials Work

December 2007 page 146
Michael J. Harley

Daniel O’Connell, Teacher and Slate Sundial Maker

This article details an 1853 slate sundial by Daniel O’Connell, a teacher from Rathmines National School, Dublin, later of Shrule, Co. Mayo. The elaborate dial, now in the National Museum of Ireland, functions as a horizontal dial, geographical clock, perpetual almanac, quadrant of altitude, and circumferentor. It is considered a teaching aid and highlights O'Connell's master engraving skills.
Dials: Horizontal, How Sundials Work, Historical Dials

December 2007 page 151
J. P. Lester

Newbury Meeting 2007

This report summarises the British Sundial Society's Newbury meeting, which began with a tribute to the late Dr. Margaret Stanier. Presentations included stained-glass sundials, mounting a vertical sundial with a TV bracket, mathematical proofs for hour lines, a schools programme for dialling, universal equinoctial ring dials, dipleidoscopes, dials with vertical gnomons, and hemispherical dials.
Dialling Tools, How Sundials Work, Sundial Design & Layout, The BSS and Members

December 2007 page 164
Hugh McCague

The Method of Equal Altitudes or the Indian Circle

This article describes and historically surveys the method of equal altitudes, also known as the Indian Circle, used for determining the meridian and cardinal directions by observing a gnomon's shadow. It covers the practical steps, potential errors, mathematical analysis of shadow curves (conic sections), and its widespread use in ancient and medieval Eastern (India, China) and Western (Roman, early medieval Europe) cultures for architecture, town planning, and sacred rituals.
Historical Dials, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

December 2007 page 172
John Davis

Clock Ephemera and Sundials

This article discusses the historical connection between clocks, watches, and sundials, referencing an example on the cover. It examines images from J.W. Benson Ltd catalogues featuring sundials, including a horizontal sundial with a truncated gnomon creating a nodus. The author speculates whether these depicted dials are real or artistic creations.
Dials: Horizontal, Historical Dials, How Sundials Work

February 2006 page 6
Karl G. Hofbauer

‘The Moon Has Set And The Pleiades’ - Sappho; Time Measurement in Cultural History

Drawing on Sappho's poem, this article explores the history of time measurement, from ancient astronomical principles to modern atomic clocks. It examines the evolution of the term 'hour,' different timekeeping systems (Babylonic, Italic, canonical, equal), and how celestial phenomena like moon phases and the Pleiades were interpreted to determine time and seasons.
How Sundials Work, Historical Dials, Dials: Nocturnals

June 2006 page 91
Graham Aldred

A Review of the Heliochronometers by Pilkington & Gibbs: Pt.1 - The Design and Accuracy of the Gibbs Helio-Chronometer

This first part of a review examines the design and accuracy of the Pilkington & Gibbs Helio-Chronometer, an equatorial sundial known for its mean time accuracy. It details the instrument's components, mounting assembly, sight screen system, and the mechanism for integrating the Equation of Time using a cam, and discusses factors affecting its long-term accuracy, such as wear and calibration.
Dials: Heliochronometer, Equation of Time, How Sundials Work, Sundial Design & Layout

September 2006 page 132
Ian Hinton

Church Alignment: Towards Patronal Saint Sunrise?

This research article investigates the theory that churches are aligned towards the sunrise on their patronal saint's feast day, based on a comprehensive survey of 1670 churches. The study considers factors like horizon elevation and calendar drift, concluding that the majority of churches consistently align towards true east, rather than their specific saint's day sunrise.
How Sundials Work, Historical Dials

September 2006 page 140
John Moir

Update on the Horniman Ceiling Dial

This article provides an update on the Horniman ceiling dial, a reflected sundial installed in a wooden building. It discusses ongoing monitoring and a recent recalibration due to timber movement. An innovative technique using a balloon to cast a shadow and make the light spot visible during low winter sun conditions is also highlighted.
Dials: Reflected, How Sundials Work

December 2006 page 164
Jill Wilson

Understanding Sundials: Farncombe Estate, 18-20 August 2006

Jill Wilson reports on a successful weekend course on 'Understanding Sundials' at Farncombe Estate. The curriculum covered the history of dialling, fundamental theory, design principles, practical delineation using various tools, and the practicalities of installing dials, with a focus on wall declinations. Attendees, from beginners to experienced diallists, gained new insights and appreciation for sundials.
How Sundials Work, Mathematics of Dialling, Sundial Design & Layout, The BSS and Members

December 2005 page 142
Christopher Daniel

The Equation of Time: The Invention of the Analemma. A brief history of the subject (Part II)

This part of the article discusses the history and application of the analemma in equinoctial sundials, particularly in Great Britain and the Netherlands. It details inventions by Major-General John Ryder Oliver, William Pilkington, and William Homan, and provides strong evidence suggesting Johann Philipp von Wurzelbau invented the analemma around 1716, predating Jean-Paul Grandjean de Fouchy.
How Sundials Work, Equation of Time, Historical Dials, Dials: Heliochronometer

December 2005 page 155
John Wall

Reader’s Letter

A reader poses a hypothetical question about the consequences for gnomonics if the Earth rotated in the opposite direction. He notes that sundial hour-line numerals would need to be reversed and invites other readers to submit lists of possible effects, offering a reward for the most comprehensive list.
How Sundials Work

December 2005 page 159
Jill Wilson

CD-ROM Review

This review covers Tony Moss's PowerPoint CD-ROM "Sundial Presentations," which includes "Concepts for Students of Sundialling" and "Using and Understanding Sundials." It praises the CD for its clear, animated slides explaining basic sundial concepts, theory, alignment of gnomons, differences between clock and sun time, and the analemma, making it useful for beginners and lecturers.
Book Reviews, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

March 2004 page 4
Mike Cowham

Do We Need Shadow Sharpeners?

Explores methods to improve the precision of reading sundials, addressing the problem of the penumbra (fuzzy shadow) caused by the sun's finite disc. It discusses various gnomon designs, such as annular gnomons for noon marks, thin rod gnomons, and pinhole or taut wire gnomons, which create sharper shadows for more accurate time-telling.
Dials: Noon Lines, Dials: Portable, How Sundials Work, Sundial Design & Layout

September 2004 page 91
Heiner Thiessen

Vial Dial

Description and design of an equatorial ‘vial’ ring dial that combines a planisphere with a sundial. Uses a spirit-level alidade and a rotating outer ring to read local apparent time for any longitude, and to estimate sunrise, sunset and the locus of solar midnight across longitudes.
Dials: Equatorial, How Sundials Work, Sundial Design & Layout

September 2004 page 103
Karl G. Hofbauer

A sun and moon dial with Babylonic and Italian hours

Description of a multi-plane stone dial ensemble that shows Babylonian and Italian hours by day and acts as a moon dial at night; discusses decorative Earth/moon motifs, orientation relative to local and Basel reference planes and how the lunar readout is used.
Dials: Horizontal, Dials: Unusual, How Sundials Work

December 2004 page 146
Mike Cowham

Dialling made (almost too) easy

Practical method using a 24-hour equatorial template to transfer hour lines to arbitrary surfaces. Demonstrates template folding for latitude, a Cambridge horizontal example, spherical and heart-shaped scaphe dials, marking equinox/solstice lines and gives practical tips on template rigidity and common pitfalls.
DIY Sundial Projects, Dials: Scaphe, How Sundials Work, Sundial Design & Layout

March 2003 page 3
David M. Colchester

John Constable's Rainbows Over Salisbury Cathedral and Stonehenge

Analysis of John Constable’s paintings using principles of sundial geometry to determine whether the rainbows depicted are optically accurate and temporally consistent.
How Sundials Work

March 2003 page 33
John Foad

To Estimate the Declination of a Dial

Method for determining the declination of a sundial using shadow observations and calculations, useful for dating or assessing alignment.
How Sundials Work, Mathematics of Dialling

December 2003 page 148
John Davis

The Gnosall Dial

Analysis of a 1721 dial with unusual semicircular scales used to estimate sunrise and sunset times; includes mathematical reconstruction of how the dial may have been intended to work.
Dials: Horizontal, Historical Dials, How Sundials Work

March 2002 page 7
Fred Sawyer

The Foster-Point Sundial: Time in a Perfect Round

Explains the design of a novel sundial based on Samuel Foster's 17th-century concepts, with modern adaptations and detailed geometry, incorporating latitude, longitude, equation of time and daylight savings time adjustments.
Dials: Horizontal, How Sundials Work, Mathematics of Dialling

March 2002 page 39
Allan A. Mills

Calendar Dials

Explores dials intended to show the date rather than the time, by reading the shadow of an equinoctial ring on a scale on the stile.
Dials: Polar, Dials: Unusual, How Sundials Work

March 2002 page 41
Mike Cowham

Extending the Useful Range of a Sundial

Suggests addition of vertical 'fences' to a horizontal dial to increase the legibility of the shadow for early and late hours.
How Sundials Work, Sundial Design & Layout

December 2002 page 141
Heiner Thiessen

Sunrise Dial

Description of an interactive, educational sundial model representing Earth and showing local apparent time, sunrise/sunset, solar declination, and more.
DIY Sundial Projects, Dials: Equatorial, How Sundials Work

February 2000 page 3
Allan A. Mills

Graeco-Roman Sundials, Part 1: Dials Based on the Sphere

Explores early Greek and Roman hemispherical and hemicyclium sundials, their geometry, historical usage, and accuracy.
Dials: Hemispherical, Historical Dials, How Sundials Work, Mathematics of Dialling

June 2000 page 64
Allan A. Mills

Graeco-Roman Sundials, Part II: Conical and Other Forms

Continues an exploration of ancient sundials, focusing on conical types and their mathematical construction and historical context.
Dials: Scaphe, Historical Dials, How Sundials Work, Mathematics of Dialling

October 2000 page 109
Mario Arnaldi

Medieval Monastic Sundials with Six Sectors: An Investigation into Their Origin and Meaning

Explores the historical and liturgical rationale behind medieval six-sector sundials, their canonical hour divisions, and theological symbolism.
Dials: Mass Dials, Historical Dials, How Sundials Work, Mathematics of Dialling

October 2000 page 142
Allan A. Mills

Backwards Motion of the Shadow on a Sundial

Explains the rare conditions under which a sundial shadow can appear to move backward, at specific dates and latitudes, including astronomical and observational factors.
How Sundials Work, Mathematics of Dialling

October 1999 page 118
John Wall

The Sunrise Line

This article explores the 'Sunrise Line', defined as the boundary between day and night (the Terminator). The author dislikes the term 'Terminator' and proposes 'soloriensorbis' (sunrise semi-circle). It discusses how the line moves due to Earth's rotation and its appearance on a 2D map as a shallow 'S' shape. The article also touches on determining the first territory to greet the new millennium based on sunrise time, and queries how sundials perform at sunrise on mountaintops.
How Sundials Work

February 1998 page 30
Michael Lowne

Reflecting Sundials

Describes novel non-shadow dials using reflectors. Parabolic and cylindrical forms generate bright caustic lines on a screen; hour indication follows motion of the cusp or inner edge. Includes formulae, constructional notes and an aperture version using a sundial curve.
DIY Sundial Projects, Dials: Reflected, How Sundials Work, Mathematics of Dialling

January 1997 page 2
Fred Sawyer

Samuel Foster of Gresham College - The 1996 Andrew Somerville Memorial Lecture

A detailed biographical and technical account of Samuel Foster, a 17th-century diallist, highlighting his innovations in dialling techniques, instruments, and his influence on later gnomonists. Explores historical context, plagiarism controversies, and posthumous publications.
How Sundials Work, Mathematics of Dialling

January 1997 page 37
J. T. R. C. Schepman

How to Determine Time by Moonlight

A method for telling time using moonlight and sundial principles. Explains necessary calculations, lunar phases, and adjustments for accuracy.
Dialling Tools, How Sundials Work

April 1997 page 24
Colin J. Thorne

Altitude Dials at Extreme Latitudes

An exploration of altitude dials designed for high-latitude locations, discussing their construction, adaptations, and challenges in time-telling under extreme solar conditions.
Dials: Portable, How Sundials Work, Sundial Design & Layout

July 1997 page 10
John Davis

When the Sun Shines

An article discussing the amount of actual sunshine received in a given year in Ipswich, England, compared to the theoretical maximum. It includes graphs of daily sunshine data from 1996 and notes how environmental factors like trees can affect a sundial's performance.
How Sundials Work

February 1996 page 9
Peter Lamont

Open Book and Conical Dials

An exploration of innovative sundial designs such as the Open Book and Conical types, combining mathematical precision with aesthetic appeal.
DIY Sundial Projects, How Sundials Work, Sundial Design & Layout

February 1996 page 22
Allan A. Mills

Sunlight and Shadows

Scientific explanation of the principles behind shadow movement and sundial timekeeping, with educational value.
How Sundials Work

June 1996 page 10
Girolamo Fantoni

Azimuth Sundials Horizontal and Vertical

An in-depth exploration of azimuth sundials, comparing projection methods, construction techniques, and their advantages, with historical and modern examples.
Dials: Horizontal, Dials: Vertical, How Sundials Work, Mathematics of Dialling

June 1995 page 45
Stuart R. C. Malin

Plain Sundials

A discussion on simple and understated sundials, their form and function, with commentary on their aesthetic and scientific purity.
How Sundials Work, Sundial Design & Layout

February 1994 page 8
J. G. Freeman

A Method of Determining the North and Latitude

Describes a method using stereographic projection to determine true north and latitude from solar shadow observations. Includes theoretical explanation and practical setup.
How Sundials Work, Mathematics of Dialling

June 1994 page 15
Martin Barnes

A Not So Modern Myth

This short article investigates a persistent myth regarding the orientation of hour lines on sundials. The author examines the historical origins of the misconception and clarifies the mathematical and astronomical principles that debunk it, providing a concise lesson in accurate sundial theory.
How Sundials Work

June 1994 page 22
Charles K. Aked

The Uranical Astrolabe of John Blagrave

A scholarly exploration of the design and function of a unique astrolabe developed by the 16th-century English mathematician John Blagrave. The article explains its astronomical foundations, innovative features, and historical context, linking it to broader developments in Renaissance scientific instrumentation.
Dials: Astrolabe, Historical Dials, How Sundials Work

February 1993 page 32

The Equation of Time - Nonomoil

This tongue-in-cheek article introduces 'Nonomoil,' a new product designed to simplify sundial readings by reducing the friction of the shadow on the sundial surface, thus avoiding the discrepancies between sundial time and Greenwich Mean Time. It explains how this annual treatment enhances accuracy and avoids sarcastic comments from onlookers unfamiliar with the Equation of Time.
Dialling Tools, Equation of Time, How Sundials Work

February 1993 page 36
Fred Sawyer

Bifilar Gnomonics

This paper elaborates on the theory and construction of bifilar sundials, a twentieth-century type invented by Hugo Michnik. It highlights their equiangular hour-lines, allowing direct reading of standard clock time by simple daily adjustment, and explains how time is indicated by the intersection of shadows from two horizontal threads.
Dials: Bifilar, Dials: Unusual, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

June 1993 page 33
C. Philip Adams

The Celestial Sphere

This article describes a three-dimensional model of the celestial sphere designed to clarify astronomical and gnomonic phenomena. It explains fundamental concepts like the apparent movements of the sun, mean solar time, and the components of the model, including great circles, axis, earth, and movable equator/ecliptic. The article demonstrates how the model illustrates the sun's rising and setting, and the factors contributing to the Equation of Time.
How Sundials Work

October 1993 page 23
J. G. Freeman

Determination of Local Solar Time by Observing a Shadow on Three Occasions

This article presents a geometric method for determining three unknowns (direction of North, latitude and today's solar declination) from three angular measurements of a vertical pole's shadow. It outlines the mathematical formulae and step-by-step calculations required to find the three unknowns.
How Sundials Work, Mathematics of Dialling

June 1992 page 37
Jane Walker

Make a Sundial

This article describes the development of the 'Make a Sundial' educational book by a British Sundial Society group, initiated in response to the National Curriculum requiring primary children to understand and construct sundials. The book, produced using desktop publishing, offers projects for constructing sundials from common materials, suitable for various educational levels.
How Sundials Work, Book Reviews, DIY Sundial Projects, The BSS and Members

October 1992 page 5
Allan A. Mills

The Scratch Dial and its Function

This article proposes that scratch dials, often found on old church walls, are effective "event markers" rather than precise timekeepers. It discusses their radial geometry, common south-facing position, and erosion due to acid rain. The article refutes theories about them being equal-hour sundials with bent gnomons, and explains their connection to seasonal hours and monastic prayer times.
Dials: Mass Dials, Historical Dials, How Sundials Work

October 1992 page 25
H. R. Mills

A Portable Polar Sundial

This article introduces a portable polar sundial design that overcomes the issue of an infinitely long dial face for extreme hour angles. It uses two end-styles, which cast shadows for forenoon and afternoon hours, respectively. The dial can be adjusted using a wedge to correct for the Equation of Time or longitude.
DIY Sundial Projects, Dials: Polar, Equation of Time, How Sundials Work

October 1992 page 27
Bernard Oakley

Dialling on Uranus

This article explores hypothetical sundial behaviour on Uranus, where the planet's axis tilt is almost 90 degrees. At solstices, the sun would appear stationary overhead at the pole, and a rod gnomon would cast no shadow. As the sun moves, shadows would form circles, indicating a sidereal day, with significant changes in day length at solstices, leading to a "missing" solar day.
Dials: Unusual, How Sundials Work, Mathematics of Dialling

February 1991 page 10
Allan A. Mills

Aligning the Gnomon.

Addresses the critical step of setting up an equal-hour sundial and suggests that aligning by observing Polaris, the pole star, can be a quicker and more accurate method. Simple tools like a peep-sight or telescope can be used for this purpose.
How Sundials Work, Dialling Tools

July 1991 page 3
Andrew R Somerville

The Hampton Court Dial of John Marr, 1631 (Part 3)

This article, written in 1631, details using John Marr’s Hampton Court Dial. It explains determining celestial metrics like ascensionall difference, azimuth, amplitude, sun's altitude and declination, and Judaical hours. It also covers comparing unequal to equal hours, finding the day of the month, and predicting London Bridge tides via the dial's shadows, showcasing its comprehensive historical applications.
Historical Dials, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

July 1991 page 8
George P. Woodford

Look at it This Way - Again

This article re-examines plane dials tilted from the horizontal, focusing on clarity, legibility, and environmental compatibility. It explains 'shadow regimes,' how tilt relates to equivalent latitude, and the impact on sun-shadow patterns. Key considerations include local horizons and the 'night factor'—periods where the dial cannot register time. It highlights the clarity of polar regime dials, despite seasonal limitations, for educational and aesthetic purposes.
Dials: Polar, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

July 1991 page 13
H.W. Van Der Wyck

The World Upside Down

This essay explores the Northern Hemisphere bias in gnomonics and common perceptions, such as clockwise movements. The author describes his quest for Southern Hemisphere sundial information, noting the lack of specific literature and the 'anticlockwise' appearance of the sun and shadows there. He recounts finding an 'upside down' map of New Zealand, illustrating the profound difference in perspective for Southern Hemisphere dwellers.
How Sundials Work, The BSS and Members

October 1991 page 3
Andrew R Somerville

The Hampton Court Dial of John Marr, 1631 [part 4]

This text reproduced from 1631 continues John Marr's description of the Hampton Court sundial. It details how to determine various astronomical propositions, such as sunrise, sunset, day/night length, and the Sun's position, using the dial's concave surface and its markings. It also explains how to find the hour of the night by observing stars on the meridian.
Historical Dials, How Sundials Work

October 1991 page 15
Pat Briggs

General Notes on Sundials (Hour Angle Types)

This note provides succinct facts about hour angle sundials. It covers topics such as local time variations, the twelve-hour day at equinoxes, dial portability, effects of rotation, limitations of different dial types, gnomon orientation, and the daily and annual changes in sunrise/sunset times and the Equation of Time.
Equation of Time, How Sundials Work

October 1991 page 24
Fred Sawyer

A Self-Orienting Equiangular Sundial

Fred Sawyer presents a self-orienting equiangular sundial, a modification of the Foster-Lambert hybrid dial, capable of correct orientation without external devices. It functions as both a solar clock and a solar compass, determining true celestial north. The design involves a V-shaped gnomon and two sets of hour-markings, allowing for simultaneous readings of Standard and Apparent time and a straightforward orientation process.
Dials: Foster-Lambert, How Sundials Work, Sundial Design & Layout

October 1991 page 31
Peter I. Drinkwater

Curiosities of Dialling

Peter Drinkwater explores historical methods of time determination, focusing on the "Shadow Square" and "Instrumentum Horarum" found on astrolabes and quadrants. He discusses ancient shadow scales, like those from Palladius, and how they were used to estimate time by shadow length, noting the practical, though often imprecise, methods employed by medieval laborers and pilgrims without modern instruments.
How Sundials Work, Historical Dials

October 1991 page 37
J.A.F. de Rijk

A New Latitude-Independent Sundial

J.A.F. de Rijk describes a new, simple, and more accurate latitude-independent sundial, building upon Freeman's 1978 solution. This type of sundial can indicate local apparent solar time without requiring knowledge of the observer's latitude. The article explains the mathematical principles, focusing on how the product sin(Az)cos(h) and sin(T)cos(δ) are obtained and combined to determine the time (T).
Dials: Unusual, How Sundials Work, Mathematics of Dialling, Sundial Design & Layout

February 1990 page 4

A Method of Finding with Increased Accuracy the Position of Shadows Cast by the Sun.

This article, an extract from The Observatory, proposes a method to improve the accuracy of observing shadows by precisely determining the boundary between the shadow and half-shadow using a piece of cardboard on a white screen. This technique can demonstrate the Earth's diurnal motion in seconds and accurately find the noontide shadow position to detect small changes in the Sun's altitude. The author speculates if a similar method was known in pre-telescope times, possibly in connection with structures like the Great Pyramid.
How Sundials Work

February 1990 page 20
George P. Woodford

Look at It This Way.

This paper explores the concept of "regime angle" in sundials, defined as the angle between the style and the dial surface. It introduces the idea that the Earth itself acts as a "show case" for various shadow regimes and illustrates how shadow curves change with latitude, showing examples for locations from the North Pole to the South Pole. The article also features Mr. Woodford's "Amundsen" dial
Dials: Unusual, How Sundials Work, Mathematics of Dialling

June 1990 page 17
Peter I. Drinkwater

Understanding the Lambertian Circles

This article explains the construction and practical application of Lambertian Circles in analemmatic dials. These circles, plotted from a specific centre through the foci of the hour point ellipse, determine the times of sunrise and sunset for any given day, applicable across different latitudes.
Dials: Analemmatic, How Sundials Work, Mathematics of Dialling

October 1990 page 26
George P. Woodford

Q for Question

This article, presented in a question-and-answer format, describes a didactic hemispherical sundial that models the Earth's relationship to the sun. It explains how the shadow of a bead indicates date and time, distinguishes it from ancient Greek dials, and clarifies why it needs occasional adjustment about its axis to display clock time.
Dials: Hemispherical, Equation of Time, How Sundials Work

October 1990 page 31
Charles K. Aked

The Nelson Touch?

This article humorously discusses a correspondence in The Times concerning an April Fool proposal to turn Nelson's Column and Trafalgar Square into a giant sundial commemorating the Battle of Trafalgar. The correspondence critiques the impracticality of such a design based on gnomonic principles, while also providing historical details on timekeeping during the battle.
Dials: Horizontal, Historical Dials, How Sundials Work