Welcome to the home of the 8-meter Sundial at 91ÑÇÉ« Campus! Photographs coming soon, we expect installation at the end of Summer 2026! Our design is based on the famous Schmoyer sundial, but there are differences between the Schmoyer and 91ÑÇÉ« sundials. According to our sundial designer Dr. R.L Kellogg, both tell accurate civil time because (1) the equatorial hours are adjusted for longitude from the time meridian and (2) the analemma shape (stretched or not) allows the seasonal correction of the sun's apparent variable motion (technically called the Equation of Time).
The Sundial Story
Dr. Robert Stairs was Trent University’s first chemistry professor, joining the faculty in 1964 and helping to build the department from its earliest days. He served twice as department chair during a 26-year academic career. Professor Stairs remained active after his retirement in 1990, lecturing and continuing a modest research program. Along with his late wife Sibyl, he established the Stairs Lecture in Chemistry at Trent University to bring distinguished scientists to campus.
After a visit to the 91ÑÇÉ« Allan I Carswell Observatory in 2021, Professor Stairs decided to help us bring back a sundial to the 91ÑÇÉ« campus. In the 1980's 91ÑÇÉ« was home to a massive interactive sundial that was an educational and outreach feature for students and the public. To bring back this kind of facility, a sundial inspired by the small Schmoyer Sunquist Sundial design (shown below) atop the observatory atrium was chosen.
Professor Stairs donated the entire construction cost for a new 8-meter diameter sundial to be installed at 91ÑÇÉ«. This sundial will be accurate to within a few minutes, and directly in line with the Allan I Carswell Observatory at 91ÑÇÉ«'s Keele Campus.
If the weather is bad/cloudy/rainy the sundial may not be able to gather enough light to tell the time. If you are planning to visit the sundial either by yourself or for an Allan I Carswell Observatory tour please check the weather before you travel.
You are NOT required to bring any telescopes or equipment to the fair as we will have several stations open with telescopes for public viewing. If you would like to assist/volunteer for the fair and bring a telescope for viewing please email the observatory director Dr. Hyde at eahyde@yorku.ca
The Sundial itself is always open, however, any Allan I Carswell Observatory public outreach events will require tickets so that we can estimate numbers of attendees. For outreach events and tickets see the main observatory website.
The 91ÑÇÉ« Sundial is based on the Sunquest Sundial, invented in 1958 by Richard Schmoyer. Our design was altered and 'scaled up' by Dr. R.L Kellogg, Vice President of the , a not-for-profit volunteer organization.
The drawing and explanation of the original Schmoyer sundial appeared in The Amateur Scientist of Scientific American in October 1959. The sundial, approximately 2 1/2 feet (76 cm) in diameter, is a truncated armillary sphere sundial. The 91ÑÇÉ« sundial follows this basic design but with slightly shorter meridian and equatorial arcs. The 91ÑÇÉ« equatorial arc was widened to show time in both Roman and western numbers. Western numbers show standard time and Roman numbers mark daylight savings hours.
The Schmoyer dial allowed the equatorial arc to be shifted and set for a longitude correction. Likewise, the 91ÑÇÉ« sundial equatorial has been corrected for longitude. At 4.5 degrees west of the 75th meridian (for Eastern Standard Time), the correction is 18 minutes of time. Thus the center of the 91ÑÇÉ« equatorial arc where it crosses the meridian is centered at 12:18pm.
Where Schmoyer used a base that clamped the meridian arc to allow setting of the polar axis to the site's latitude and point to the north celestial pole, the 91ÑÇÉ« sundial base had to be much more robust, yet still following the style of the Schmoyer sundial. The meridian arc is permanently titled to 44.7743 degrees, the latitude of 91ÑÇÉ«.
The Schmoyer dial is distinguished with a gnomon consisting of a curved left and right flange creating a slit in the center that approximates the shape of the analemma. The shape shifts the sunlight beam according to the seasons and adjusts for the sun's apparent variability. This unique gnomon corrects local solar time into civil time.
But as Schmoyer points out "The gnomon slot curve has been 'stretched out' axially at both the northern and southern end." Although claiming improved accuracy, it actually made the fabrication of the gnomon easier. There is a consequence to the stretching of the analemma. About 2 weeks before to 2 weeks after the summer or winter solstice the gnomon has to be moved daily to tell the correct civil time. This may be acceptable for a small sundial in the garden, but at the size and weight of the 91ÑÇÉ« sundial, this approach was totally unacceptable.
A good deal of experimentation went into the 3D model with feedback from the SeaWest engineers. Through several months of design, the 91ÑÇÉ« sundial emerged with a gnomon looking very much like the Schmoyer sundial, but has an analemma shape without stretching. This eliminates the complication of moving the gnomon north or south along the polar axis during the solstice seasons. Even the most mathematically correct analemma curve cannot create a spot of light to tell perfect time near the solstices, but it is just as accurate as the original Schmoyer Sunquest dial.
SeaWest engineers, particularly Andrew Schutte, went to great lengths to balance the 91ÑÇÉ« sundial gnomon so that it, like the Schmoyer gnomon, can be rotated to face the sun.  While the Schmoyer gnomon can be turned easily by hand, the 91ÑÇÉ« Sundial gnomon, with analemma slit 3.46 feet (1m) long and weighing [ask SeaWest how much the bronze gnomon weighs] is turned using a wheel on the polar axis.
Both the Schmoyer and 91ÑÇÉ« sundials are interactive and tell the time the same way: At whatever hour of the day, the east flange of the gnomon is turned to face the sun from June 22 to Dec 21. Likewise, the west flange of the gnomon is turned to face the sun from Dec 21 to June 22.
For more information, or if you have questions not answered by this webpage you can email the observatory at observe@yorku.ca
Resources:
- Join in the fun with the AICO Foldable Sundial, the free printable file is here!
- Watch the bronze being poured (coming soon!)
- The Sundial at 2026 AstroFair (coming soon!)
