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.
Instead 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 Casalegno
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
I 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
The 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.
I’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.
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
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.
--- Gone ---
The North American Sundial Society held its 2012 conference in Asheville NC, August 16-19. Alice Io Oglesby and Hugh Munro, local hosts and sundial enthusiasts, took NASS members on a sundial tour through Asheville and the rolling hills of western North Carolina to see the vertical dials at Sunny Point Café and the analemmatic dial of the “kitchen garden” at the Biltmore Estate. In Burnsville, NASS members saw the Quilt Block Sundial, one of over 200 colourful quilt block paintings along the North Carolina Quilt Block Trail. NASS was welcomed by the Mayor of Burnsville and had the Quilt Block sundial explained by Bob Hampton, astronomer designer and Martin Weaver artist. The Quilt Block Sundial in Burnsville was a most impressive example of teamwork and community support. Travelling further, Brian Leonard showed the armillary sundial he fabricated and installed in Marshall, NC.
The NASS conference included exciting talks on a colourful “Parallel Time East West Sundial” presented by new NASS member Peggy Gunnerson and shadow alignments at Toshogu Shrine by Barry Duell of the Tokyo International University. Frank King talked about a most unusual circular analemmatic dial he designed for the Metropolitana of Naples (an Italian job). Dr. King was also this year’s recipient of the Sawyer Dialing Prize. Roger Bailey discussed dials of Mallorca and the “Box of Sapphires”, a compendium designed by Ibn al-Shatir in the 14th century. Fred Sawyer gave a most interesting talk on “Projected Refraction Sundials with Ambigram”, and at the NASS dinner on Saturday, he distributed a special gift to NASS participants: a location specific projected refraction sundial with the ambigram showing “CARPE” on the dial and “DIEM” in the projected shadow. Other speakers with interesting presentations included Alice Io Oglesby, Bill Gottesman, Dudley Warner and Ken Clark. Next year’s conference is being planned for Boston.
Photos shown: (Top) NASS conference participants underneath Bob Hampton's Quilt Block Dial; (Bottom Left) NASS members examine Alice Oglesby and Hugh Munro's vertical dial at Sunny Point Cafe; and (Bottom Right) Bob Hampton's Equatorial Dial made from a bent yardstick.
The 2012 Sawyer Dialing Prize was awarded to Frank King at the annual NASS Conference in Asheville, North Carolina.
The award is given “In recognition of his innovative mathematical and astronomical solutions to problems encountered in the modern design of notable sundials.” Dr. King is Council Chairman of the British Sundial Society, Senior Lecturer of the Computer Laboratory at Cambridge University, and a Fellow of Churchill College where he is Chairman of the Churchill Archives Committee and Praelector. At Cambridge he also holds the responsibility of the University Bellringer, “one of the University’s most ancient and unusual posts” with the job of keeping the University Clock telling correct time.
He has designed many sundials including the vertical dial with Italian and Babylonian hours for Selwyn College, Cambridge (a new dial for Old Court), the Pembroke College vertical sundial, the noon mark wall analemma at 10 Paternoster Square in London, the unusual near-horizontal gnomon sundial as a memorial dial for Margaret Stanier, the analemmatic dial for Queen Elizabeth II Jubilee (2002) and the circular analemmatic dial for the MetroTransit Authority (Metropolitana) of Naples.
Frank was presented with a cash prize of $200 and a custom made Spectra Sundial by Jim Tallman of Artisan Industrials.
Seattle: Sundial Capital of the United States? The 2011 North American Sundial Society had perfect blue-sky weather for its annual conference held in August 2011. Professor Woodruff “Woody” Sullivan, conference host at University of Washington started the fest by showing off the large vertical sundial built in 1994 on the side of the Physics and Astronomy Building.
The conference covered a wide range of topics including two presentations on stained glass sundials, the 17th work of La Hire and his successful "La Gnomonique ou L'art de tracer Des Cadrans" ("Gnomonicks or The Art of Shadows of Sundials") and dialist-surveyor and one of the founding members of the Acadamie Royale, Jean Picard. The methods of taking photos of the sun over months of time, called Solargraphy, was presented by Art Paque, and then there were talks on the operation of cylindrical sundials, sundials that can show standard time, an update on the Mars sundial, and discussions on solar alignments, heliodons and stair shadows.
Helmut Sonderegger, this year’s recipient of the Sawyer Dialing Prize discussed the Rheticus Memorial sundial designed for Georg Joachim Rheticus, the first Copernican.
Download the PDF and read about the conference in detail, including the bus tour of Seattle dials visiting the Pillar Dial of University Prep Academy, Epiphany School Vertical Dial, and Rebecca Cummins analemma and colored skylights in the ceiling of the Montrose Public Library.
A great loss has hit our gnomonic community in Italy. Our friend Giacomo Agnelli died about a week ago. Giacomo was one of the great gnomonists of the past. He had written dozens of articles in engineering and horology, also dealing with mechatronics [mechanical] sundials. He had worked at the European space project, and had frequent ...articles for our magazines [on] gnomonics. He had participated in all meetings of horology in Italy and was known for his satirical cartoons and gnomonic caricatures ...
Nicola Severino Visit A Tribute to Giacomo Agnelli
This year's Sawyer Dialing Prize awarded at the 2011 NASS Conference in Seattle Washington was given to Helmut Sonderegger, "In recognition of his ongoing development and support of the dialing software Sonne, and his many years of leadership in his national society." His acceptance talk was on one of the first Copernican followers, Rheticus.
For many years Helmut Sonderegger has been active in the German Sundial Association and was chairman of a team of dialist to produce the 3rd Editiion of the Austrian Sundial Catalogue. His most famous free sundial software, „Sonne“ calculates about 20 different sundial types and his program „Alemma“ is devoted to the calculation of analemmatic sundials. The software is available at his website, www.helson.at. He endeavors to help people who make sundials through his software and through articles in the NASS Compendium and the German Rundschreiben, and for local groups.
Helmut was presented with a cash prize of $200 and a custom made Spectra Sundial by Jim Tallman of Artisan Industrials.
Along with her husband, Mrs. Webster spent much of her life and fortune combing auction catalogs and antiquarian shops to create a collection of early scientific instruments so renowned, it is considered in the same company as the Museum of the History of Science at Oxford University and the National Maritime Museum in Greenwich, England, according to Bolt, Adler planetarium vice president for collections. The Websters are primarily responsible for the world-class collection of scientific instruments at the Adler.
NASS is supporting the Adler to catalog their sundial collection enhanced over the years by Marjorie Kelly and her husband.
Sundials for Starters
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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.
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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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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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