1026 ky louisville cavehill ztaylor 2aSuppose that you've purchased a commercial sundial and you want to make it work correctly for your latitude.  Further, you don't live on your time zone meridian, but are some kilometers/miles east or west of that longitude line. 

Steve Lelievre has written a web app that allows you to build a wedge to hold the sundial.  You can use the calculator to simply make a latitude wedge to compensate the dial latitude and your latitude, but Steve's app does a lot more.  It corrects for you longitude by performing two rotations: (1) the dial is rotated by a specified angle on the face of the wedge, then (2) the whole dial and wedge are rotated by a second specified angle.

The result is that your sundial wll now tell accurate solar time at your time zone meridian!   This is a very handy calculator: Go to: https://gnomoni.ca/wedge/

Ventura Mission SundialDr. Jessica Warren, lecturer of physics and astronomy at Indiana University Northwest, is active in science outreach and education.  She is also passionate about sundials.  For Indiana University outreach shecreated a video "The Garden Sundial - Much More than an Ornament" that presents a brief history of the sundial, how they work, and where to get one or make one. 

You can watch the video on YouTube at https://www.youtube.com/watch?v=K10nPV69Q1A.  It is also part of the North American Sundial Society library of videos, found on this website at https://sundials.org/videos/making-and-using-sundials.html where NASS has a collection of videos on sundials, timekeeping, and interviews with sundialists on how they make sundials.

At the end of her presentation, Dr. Warren provides a list of reference material about sundials. Her entire video including references is available as a PDF and is available for download at the bottom of this article.  Additional references and sundial topics are available on the NASS sundial links page:  https://sundials.org/dial-links/general-sundial-links.html.  Read more about the fascinating world of sundials.

nass news 2020 jan analemmatic ellipseWritten just a decade ago Plus.Maths.org provides a good trigonometric explanation of how to construct an Analemmatic Sundial. In their introduction, "An analemmatic sundial is a particular kind of horizontal sundial in which the shadow-casting object is vertical, and is moved depending on the date, or to be more precise, depending on the declination of the sun on a given day. The time is read from the dial by noting where the shadow cast by the vertical pin crosses hour points laid out on an ellipse. If we make the dial on the ground and large enough, we can use the shadow cast by a person. This makes it very different from the traditional sundial we see often in parks and gardens where the shadow is cast by a triangular shaped wedge. The analemmatic sundial is perfect as a piece of large mathematical sculpture."

Read more and make your own sundial: https://plus.maths.org/content/analemmatic-sundials-how-build-one-and-why-they-work


871 az oro valley innovation academy 1aThe analemmatic sundial is unique with the ability to use a gnomon (the shadow casting element) of any height. This leads to the popular use of the analemmatic sundial as a "human sundial" where people use their own shadow to tell time.

Unlike garden horizontal dials or vertical dials on buildings, the analemmatic sundial requires a moveable gnomon. The position of the gnomon or where the person stands must be changed depending upon the season. A central walkway or guide indicates that a person should stand closer to the sun's noon hour mark at summer solstice and in reverse, stand much further south for the winter solstice. At the equinoxes the gnomon or person stands on a east-west line connecting the solar hours of 6am and 6pm.

nass news 2019 july solargraph 1In the NASA Photograph of the Day for 27 June 2019 is a beautiful photograph by Gianluca Belgrado using a pinhole camera. https://apod.nasa.gov/apod/ap190627.html As explained by NASA, "This persistent six month long exposure compresses the time from solstice to solstice (December 21, 2018 to June 16, 2019) into a single point of view....Fixed to a single spot at Casarano, Italy for the entire exposure, the simple [pinhole] camera continuously records the Sun's daily path as a glowing trail burned into the photosensitive paper. Breaks and gaps in the trails are caused by cloud cover. At the end of the exposure, the paper was scanned to create the digital image...."

In 2011 Art Paque explained the art of solargraphy to members of the North American Sundial Society at their annual conference in Seattle.  The construction steps involve creating a pinhole in thin foil, then taping the foil onto a tin can that has photographic paper inside and opposite the pinhole.  The lid on the can is sealed and most important, pointed at the sky with firm support to prevent moving.  The rest is up to nature as the sun crosses the sky each day.  Beautiful solargaphs such as from Gianluca can be obtained with patience tracking the sun for three to six months. In the end your solargarph will be a day by day time capsule of solar observation.

Type "solagraphy" into your web search engine and you will discover a host of sites showing the details of making your pinhole camera.  For example: http://www2.uiah.fi/%7ettrygg/camera.html and http://www.pinholephotography.org/Solargraph%20instructions%202.htm

nass news 2019 july solargraph 2

nass news 2019 june Waterloo Sundial ArchStudents at the University of Waterloo School of Architecture in Cambridge, Ontario are experimenting with the benefits of 3D design and printing. In particular Joanne Yau created a set of hexagonal hollow bricks called sundial arches that lets in sunlight from different portions of the arch as the sun travels across the sky. We expect that the length to width ratio of the bricks can tailor sunlight for specific times of the year (summer, spring/fall, or winter).

Joanne Yau was one of three teams challenged to learn how to operate a new industrial 3D printer capable of squirting out clay. Professor Correa, interviewed by 3Dprint.com said “There is no other way to make these kinds of façades without enormous cost and time,” said Correa, who has been involved in 3D printed research on an even more advanced level, studying how such objects respond when exposed to varying degrees of moisture and temperature. “They are completely unique.” “The printer allows us to make much more complex geometry,” said Joanne Yau, part of the team that 3D printed bricks for the ambitious arch/sundial. “To make this by hand or to extrude it would be virtually impossible.”

See a video of how the 3D clay bricks are created in an article by Bridget O'Neal June 5, 2019: https://3dprint.com/245698/whistling-walls-sundial-arches-ontario-architecture-students-3d-print-clay/

Teachers and Architects Draw Sundials for Baltimore SchoolsGrimm & Parker Architects sponsored a "Green Apple Day" on October 15, 2016 to help two Baltimore City Schools - Graceland Park ES/MS and Holabird Academy ES/MS - receive analemmatic sundials on their front sidewalks.  The weather was perfect as teachers and volunteers from G&P chalked out and then painted simple 16 x 5 foot analemmatic sundials.

The sidwalks were aligned true North-South, making dial lay-out easy.  With tape measures in hand, they marked out the focal points and north point of the analemmatic ellipse.  Then, using the time-honored principle of constant distance they used a chalk line between those 3 points to maneuver a piece of chalk following the shape of an ellipse.  For the sundial, the ellipse stretched from 5am to 7pm.  The hour marks were made using two tape measure to check positions that were quickly followed by drawing of the hour circles with a plastic lid.  While volunteers painted the hour circles others chalked out the walkway whose monthly lines and solstices were quickly painted as well. The final touch was the inclusion of the East and West Bailey points that determine the direction of the rising and setting sun.  With a lot of support and good organization, both dials were finished in 3 hours!

Durer Method of Making a SundialYou can layout a sundial using only a compass and straight edge (and yes, a ruler and book of tangents so that you can set out the gnomon lines for your latitude).  Clem Rutter has created a graphical set of instructions to make horizontal sundials taken from the challenge of Fred Sawyer of the North American Sundial Society to find how many different ways can you graphically lay out the lines of a sundial.

Here's where the fun begins.  Clem Rutter in short order presents eleven different approaches. Do you want to follow the method of Dürer (1525), Benendetti (1574), Clavius (1586) or the more modern methods of Leybourn (1660) or Ozanam (1673)?  All these methods are graphical shown.  Join the centuries of gnomonists and begin your own Art of Dialing at https://en.wikipedia.org/wiki/Schema_for_horizontal_dials

Armillary Sphere

An armillary sundial also called an armillary sphere is a representation of both the terrestrial globe and celestial sphere.  Often highly decorated, these are beautiful sundials.