Sundials - World's Oldest Clocks

North American Sundial Society


Fred Sawyer, in cooperation with the North American Sundial Society, established a continuing yearly award, the Sawyer Dialing Prize to be presented by NASS to an individual for accomplishments in or contributions to dialing or the dialing community. Each year a panel makes recommendations of those people who have significantly contributed to the art of dialing by their dialing art, their ability to teach and educate, their superb craftsmanship, their care in dial restoration, or in their gnomonic skills in design and computer programming tools for others.

 At each North American Sundial Society conference since 2000, the winner is announced and awarded with a certificate of recognition, a small trophy sundial, and a cash award of $200.  Many of the awardees have chosen to use their cash award to help further the art of dialing by donating it to others, increasing the scope of sundialing around the world.  Funding for this award has come from the Sawyer family with a 50% matching donation by NASS.

The certificate and trophy dial presented to each recipient are inscribed with the Greek letters ZHΘI.    The ancient Greeks used the letters of their alphabet as numerals.   When the hours of a dial were to be numbered from dawn to sunset, the numerals used were A, B, Γ, Δ, E, S, Z, H, Θ, I, IA, and IB for the successive hour intervals. By chance, the sequence from the seventh through the tenth hour (i.e. noon through mid-afternoon) spells a Greek word ZHΘI, the second person singular imperative meaning: Live!  The Greeks carried this thought further, and an epigram on the certificate, attributed to Lucian - a second century Greek satirist - exhorts:



The first three Sawyer Dialing prize recipients received a Universal Equatorial Dials designed and crafted by Tony Moss of Lindisfarne Sundials, UK. [Tony is now retired and the last of the Lindisfarne Sundials has been made.]  The dial can be set for any latitude and is a special edition containing the NASS logo and the imperative ZHΘI.

Since 2003, Sawyer Dialing prize recipients have received Spectra Sundials crafted by Jim Tallman.  Hundreds of Spectra Sundials can be located around the world at The World of Artisan Sundials - Spectra Sundial Locations Worldwide .  The unique design of each Sawyer Dial is given as an html link at the bottom of each award description.

This Sundials for Starters appeared in The Compendium in December 2013

Robert L. Kellogg, Ph.D.

Fig. 1 Analemma over the Acropolis photographed during the year by Ayiomamitis

As the shadows grow longer and we head for the winter solstice my mind turns again to the analemma, a concept invented by Grandjean de Fouchy in 1740 to describe the apparent irregular motion of the sun. Strictly speaking, this is the difference between the right ascension of the true sun minus the right ascension of the mean sun. While this is mathematically important to astronomers, it is esthetically pleasing that the apparent sun will describe a “figure 8” through annual motion in the sky. This “figure 8” or analemma is visible only when the sun’s position is compared to a “mean time” using a precise clock. The analemma (or the sun’s apparent East-West motion called the Equation of Time) allows us to answer the question “Will the time shown on my sundial be fast or slow compared with my watch?”

Read more: Analemma and the Equation of Time

Solar Eclipse - NOAACome to St. Louis for the 23rd Annual NASS Conference at the Clayton Plaza Hotel. Take the free shuttle to the hotel from the Lambert St. Louis International Airport and enjoy 3+ days of gnomonic presentations and sundial discussions.  We are planning some tutorial sessions for the afternoon of Saturday, Aug 19th and the tour this year is very special with a ring side seat to watch the August 21st Solar Eclipse.

As usual there are two registration plans: (1) full registration for all of the talks, conference dinner, and bus tour to observe the eclipse, and (2) partial conference registration that includes everything but the sundial presentation sessions.

If you have a sundial presentation or want to display your favorite sundial or book, please contact by email This email address is being protected from spambots. You need JavaScript enabled to view it.  In any event, download the registration form now.  You may pay by check or Pay Pal.

Download this file (NASS Register StLouis 2017.pdf)NASS Register StLouis 2017.pdf[ ]20 kB

Richard Mallet at Cornell Univ. SundialRichard Mallet at Cornell Univ. Sundial

Richard Mallet, former British Sundial Society Trustee, Council Member and former BSS Webmaster passed away on Nov 7th, 2016 with funeral held on Dec 12th, 2016. He lived in Eaton Bray, UK and had many interest in physics, mathematics, and sundialing.  Those of us maintaining websites know of the difficulty in perserving order, yet always allowing for expansion of new material. "After a near disaster with the [British] Sundial Society's then  heavily modified and entirely non-compliant website, Richard stepped in at no charge to the Society to rewrite it using the then new Expression Web software from Microsoft.  This proved very successful and was of course fully W3C compliant."

Over the next year, the North American Sundial Society website will migrate from an older version of  the Joomla Content Management System to the fully maintainable Joomla 3.x version.  The majority of content and organization will remain intact, but new innovations are expected.

Read more about Richard Mallet's life at:

This Sundials for Starters appeared in The Compendium in March 2007
(Updated January 2017)

By Robert L. Kellogg, Ph. D.

Benjamin Bannekar

Benjamin Banneker, 1731-1806 , is one of the nation's best-known African American inventors.  He was born in Maryland and in 1791 played an important part in surveying the newly designed Federal Territory, now called the District of Columbia.  In his youth, Banneker was inspired to build his own clock after an acquaintance gave him a watch. He took the watch apart to find out how it worked and made drawings of each component, and based on his drawings, he carved larger versions of the components out of wood and constructed a clock that kept accurate time for more than 50 years.   As mathematician, he designed an Almanac that was a rival of Benjamin Franklin’s famous publication.

As astronomer, clockmaker, and mathematician, he was expected to know how to design sundials, although none exist bearing his mark.  In an age before pocket calculators, how would Banneker design a sundial?  The graphical method is available in modern texts such as Waugh’s 1973 classic “Sundials: Theory and Construction”.  Want to lay out a horizontal sundial without sines, cosines, and tangents?  Then this “Sundials for Starters” is for you.

Download this file (Bannaker- Dial Construction.pdf)Bannaker- Dial Construction.pdf[ ]2019 kB

Read more: Bannekar - Drawing a Dial


Some years ago Bob Terwilliger built a Laser Trigon, an instrument that assists in drawing sundial lines on irregular shaped objects. For more about the Laster Trigon, see The Teacher's Corner - Sundial Projects. Here is the story of how he used it to create a bathtub sundial and after some years of service, how the sundial met its end.



The laser projects a beam of light to draw the lines and curves of a sundial onto any surface. To test the capabilities of his Laser Trigon, Bob decided to build a large combination vertical and horizontal sundial in his Florida home backyard … with some unusual consequences.  Here is his blog, taken from “A Dialist’s Notebook – The Shadow Garden

August 31, 1996 – Planning the Garden Sundial

 The Shadow Garden is an area in my back yard set aside for experiments in building sundials. The dials are transient, and all were made from found objects. Some are being built for fun - others to experiment with a method of construction.

terwilliger_garden_dial_modelInstead of putting a sundial in your garden, why not put a garden in your sundial? I am hoping the result [using the Laser Trigon] will be a fascinating and unpredictable garden of objects, some bearing hour lines, some numerals, some both, many neither. As the sun defines the day, its shadow will wend its way among them, anointing those it chooses with the power to tell time.

The first step is to make a working model. I need to get a feel for the relationship between the position of the gnomon and the west-facing board fence. The model consists of two planar dials, a horizontal dial joined to a direct west vertical dial. These surfaces will not be obvious in the finished dial, as the lines and curves will be located on the objects lying within the dial itself.

The Horizontal Dial is limited by the backyard space, such that only to the hours from10am-2pm will be seen, while the Vertical Dial to be attached to a north-south running fence will display the summer shadows to 8pm.

Next I installed the gnomon, which is made of fencing tubes and associated tee and elbow hardware. I temporarily located hour and half hour indicators on the ground by marking piles of whatever I could find.  The markers show the appropriate local solar time.

The hour line timing for this was done [with a now old] computer program, The Dialist's Companion, written by Fred Sawyer and myself for the North American Sundial Society. [Today a number of sundial calculators are available for your choosing, including:]

Orologi Solari by Gian Casalegnoterwilliger_garden_fence

zw2000 by Fer J. de Vries

Sonnenuhren by Helmut Sonderegger

Sundial Design by Miroslav Brož

A few of the objects I found to show local solar time (along with much pre-existing trash) are shown below the dial gnomon.

October 23, 1996 – Rethinking the Size of the Dial

I have to rethink this dial. If you take a look at the full size photograph, I think you will agree that the scale of the objects I used are too small for the size of the gnomon and the overall garden area.  I am going to have to find larger objects, or settle for a design that uses less shadow receiving surface.

February 21, 1997 - A Hot Tub is Found and Construction Begins

terwilliger_garden_plaintubI may have solved my problem. I found a derelict fiberglass hot tub … a discarded Jacuzzi bathtub… which has a suitable variety of surfaces and angles. Instead of many small objects, why not one big one? Tipped up on an edge, it fits almost perfectly between the posts outlining my desired dial area.

The hot tub has been tilted up facing south. It sat naturally in this position, but I provided further support so that I can walk on it without the tub moving. Drainage is provided by drilling holes in the apparent low points of the tub.

In preparation for realizing my dial, I tested the Laser Trigon on the tub. Sadly, the original laser was not bright enough to properly illuminate the surface. I have now acquired a much brighter laser, which I’m installing in the Trigon. The problem of mounting the Trigon has, in principal at least, been solved.

[Lasers have come a long way since 1997. Today, a number of 3-5mW (Cat-III) lasers are available for moderate cost.  Brighter Cat-IV lasers are available for under $1000]

March 4, 1997 – Drawing the Lines

terwilliger_trigon_photo_laserbeamThe new laser has been installed and it gives a perceptible dot. The mounting also works well, and I’ve already laid out the morning hour lines. I’ve scanned some Polaroid photographs to show the results.  The dial is being built for latitude 25° north, longitude 80° west.  My dial will include a longitude correction for the offset from the Eastern Time Zone at 75° west.

terwilliger_garden_trigonheadI’m using a sturdy tripod with a V rest on top and placed inside the tub as if to support the gnomon. Next, I’ll remove the gnomon and replaced it with the Trigon, which has been mounted on a length of the same tubing used to make the gnomon. The instrument and its tubing will be secured to the gnomon support post and rest on the tripod.  I’m including a photo of the Laser Trigon mounted on the tubing.

The instrument has replaced the gnomon and is positioned so the center of the axes of rotation is at the desired point of the nodus, a point that can be used to project the solstice limits of summer and winter and the mid year equinox line. The nodus point was somewhat arbitrarily chosen, but is close to the actual position of the nodus that will be determined more precisely by its shadow on the upcoming equinox. Another view of the process. Pepín tries his hand at the laser.

We start work at twilight, as the tub is too hot when in direct sunlight. This is our second session. Some of the lines have already been laid out and taped. I am directing the laser, Pepín is marking the position of the dot. The morning lines and three lines for declination are finished. The gnomon is back in place. The winter solstice and the equinox can be seen. The summer solstice is there, but it falls inside the tub. The lines are applied with 3M "Long Mask" masking tape. Hours and half-hours run through the tub. Quarter-hours are marked along the edges.


Interesting? It works for me.

March 15, 1997 - A minor setback

During a windstorm yesterday, a heavy extension ladder blew down and fell on the gnomon that fortunately had been removed and placed on the ground for safety!  The gnomon was bent and will have to be replaced.

April 3, 1997 – All the lines are finished

I have designed some numerals, which will be cut from vinyl by a signmaker who cuts custom letters with a plotter. The numerals will then be applied directly to the fiberglass. Gaps can be seen in the photo below for the numerals 1, 2, and 3. The time shown on the dial is just before 12:15 (the sharp eye will note - a bit after the equinox). The little numerals at the bottom are temporary.


Almost Finished

April 17, 1997 – The Finished Dial

After six days without sun, I was finally able to photograph the finished dial.  View from the south. The time is just before 11:45.  The flags are those of the State of Florida and the United States of America.


This calls for A Party. Click the audio panel below and listen to the Beatles' Here Comes the Sun.

March 20, 1998 - Performance of the Dial During its First Year

terwilliger_trigon_drawing_detailsThe hour lines were consistently accurate during the entire season. The taped lines themselves have faded slightly.

When making the Laser Trigon with my small clockmaker's machinery I encountered some problems laying out and machining the parts of the device necessary to produce the seasonal lines and curves. On the finished dial the winter solstice and equinox were reasonably accurate, the summer solstice less so. A bit of "tweaking" of the position of the nodus brought all the seasonal shadows within a half-inch or so of dead center. The results of the experimental dial were satisfactory, and some improvements to the seasonal adjustments of the Laser Trigon will produce an instrument which will, as advertised, "draw a sundial on a Buick".


April 28, 2000 – The End of the Hot Tub Sundial

The dial was completed in April of 1997. After 3 years in the direct sun, the dial has decayed. The masking tape lines have faded and washed away. I made an attempt to put vinyl tape over them, but it would not stick. Weeds have grown up through the drainage holes. Since the dial is in Florida I have filled it with concrete cylinders to prevent it blowing away during a hurricane. (I have always been amused by considering what an interesting UFO the dial would make should it fly away, and what the people who found it might think of it.)  Fortunate for all, it has stayed put.


Dial Completed in April 1997                                             Dial in April 2000

Installation and removal of the concrete cylinders during previous hurricane seasons had thrown the dial slightly out of alignment. It had never been secured to a foundation and I have always considered it temporary. The dial has survived three years without experiencing a hurricane, and I felt the odds might be against it surviving another.  In April, 2000 we took the hot tub dial down.


Going                                                        Going


--- Gone ---

Read The Seattle Times article of May 14, 2013:

nass_news_2013_may_Sullivan_DialIn the May 14, 2013 edition of The Seattle Times University of Washington professor Woody Sullivan was honored as ‘Mr. Sundial’ for his persistence in declaring Seattle as the Sundial Capital of North America. Dr. Sullivan has worked on more than a dozen dials in Seattle, including the large 20x30 foot vertical dial on southwest wall of the Physics and Astronomy building at UW and the elegant 11x17 foot reflection sundial painted on the ceiling of his garage at N 47° 41.232, W 122° 21.562.  A small circular mirror outside the south facing window reflects a spot of light onto the ceiling.

The reflection sundial was a labor of love taking over 3 years to create.  Woody marked over 700 locations on the ceiling that allowed him to draw the local solar time, dates, hours of daylight, solar azimuth and altitude, analemma, and even hours to dawn.  And being a radio astronomer, he marked the transit sidereal time for two radio sources.  The dial was painted with marvelous beauty by a local mural artist, Jim Noonan.  The sundial is very personal to Woody, showing time marks for the date he married to the birthdays of himself, his wife, and two daughters.  The zodiac painted along the ecliptic has a local touch, representing Pisces by a pair of sockeye; Cancer by a Dungeness crab; and Capricorn as a mountain goat. There is even a compass rose.

nass_news_2013_may_UW_dialFred Sawyer, president of the North American Sundial Society (NASS) is quoted by Erik Lacitis, Seattle Times staff reporter, saying “it’s likely true that Sullivan’s garage sundial is one of the best in North America.”  When the NASS visited Seattle for the 2011 annual sundial conference, they visited Woody’s Reflection Dial and a marker was added to it for the date and time of itsofficial dial dedication held on Saturday 22 August 2011. “We toasted the sundial with an appropriate wine, ‘Wehlener Sonnenuhr’ by Joh. Hos. Prum, the fine Mosel Kabinett from the German vineyard with a large vertical sundial.” said Roger Bailey, the society’s secretary.

Among Dr. Sullivan’s accomplishments in the world of sundials began in the early 1990’s when the University of Washington’s Physics and Astronomy Building was being designed.  He suggested a large vertical (southwest declining) sundial.  The dial was completed in 1994 and Woody was hooked. He also helped design sundials used on the Mars exploration rovers Sprit and Opportunity that landed ion the Martian surface in 2004.  A campaign to build sundials all around our world ensued with the motto “Two Worlds One Sun”.  [photos from NASS]

This year's Sawyer Dialing prize was awarded to Roger Bailey at the NASS annual conference in Portland, ME.  The certificate recognizes Roger for "consistently showing the dialing community that all you need to know in life can be learned from studying sundials, and for using that study to advance the theory and practice of dialing."

Fred Sawyer presented Roger with an award certificate, the traditional cash prize of $200 and a custom made Spectra Sundial by Jim Tallman of Artisan Industrials.

On receiving the award Roger's presentation was "That is a Good Question".  Here he pointed out that most of his achievements in the art and science of dialing was sparked by answering good questions, questions like the shadow lengths or the time and direction of sunrise sunset on analemmatic sundials or time systems on Islamic sundials. The theme was "Ask and you shall receive". He remains open to good questions.



  • Sundials for Starters
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  • Conferences
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  • Sawyer Dialing Prize
    Fred Sawyer, in cooperation with the North American Sundial Society, established a continuing yearly award, the Sawyer Dialing Prize to be presented by NASS to an individual for accomplishments in or contributions to dialing and the dialing community.
    Article Count:
  • Terwilliger Sundials
    In these pages is the famous tub sundial created by Robert Terwilliger using his laser trigon to lay out hour lines on a very irregular surface to create a working sundial.
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  • Biographies

    Who are today's sundial artisans?  Here are several bioghraphies of several artisans that show the unique combination of talents in art, engineering, and mathematics.

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