Every Thursday at noon central time the Adler Planetarium presnts "Adler Astronomy Live" with a variety of interesting topics and speakers.
On Thrsday Oct 8th, 2020 the series presents Dr. Sara Schechner on the topic of Time, Culture, and Social Change. As the Adler website states:
"The Adler Planetarium has the best and most comprehensive collection of sundials in North America. Sundials played a central role in shaping people’s sense of time, and show how the latter has been influenced by their culture, politics, religion, labor, society, and geography throughout the ages. Join us for a conversation with Dr. Sara J. Schechner, author of Time of Our Lives: Sundials of the Adler Planetarium, on some of the most spectacular sundials in the Adler’s collections and their stories. Set a reminder on YouTube"
Dr. Schechner is an engaging speaker with a wealth of experience in historical instruments and has a passion for sundials. Adler has recently published the beautifully illustrated book Time of Our Lives: Sundials of the Adler Planetarium. The North American Sundial Society helped underwrite the production of this book, nearly a decade in the making.
To hear the presentation live or in recording after the event, go directly the Adler's YouTube channel to find the presentation at: https://www.youtube.com/adlerplanetarium
Drawing of Horizontal and Analemmatic Sundial
"Analemmatic or Azimuthal Dial"
J.J. de LaLande 1784
The Analemmatic Sundial SourceBook was first published in 2004, revised in 2014, and now is again available in digital form on CD or by download from the north American Sundial Society. What is it? It is a very comphrehensive reference to the origins, history, and modern evolution of the analemmatic sundial compiled and edited by Fred Sawyer III, President of NASS.
It started with J.L de Vaulezard publishing a small work of 15 pages in 1640 descibing the dial in vague terms, promising to reveal its construction later "if I see that the work has been well received by you...." Four years later de Vaulezard published his "Treatis of the origin, demonstration, construction and usage of the analemmatic dial". A decade later Samuel Foster published "Elliptical or Azimuthal Horologiography" further describing the analemmatic sundial. The SourceBook reprints a facsimile of this and three other of Foster's original works.
The Historical Period includes not only the works of de Vaulezard and Foster but works by Aubri, Tuttell, Richer, Parent, Bion, Lalande, Bedos de Celle, Lambert, Oberreit, Boutereau, Meikle, Perret, Peaucellier, Viala, Lisbonne, Gruey, Marchand, Roguet and Chomard. For over 250 years these authors provide the earliest proof of the analemmatic dial, the introduction of the Foster/Lambert, diametral, and Parent variations, as well as many important historical and theoretical discussions of the analemmatic dial and its properties.
Study of the analemmatic sundial had a revival at the turn of the 20th century and again beginning in 1986 with the publication of "Equator Projection Sundials" by de Rijk. Other articles include R.J. Vinck's "Times of Sunrise and Sunset on the Analemmatic Sundial" further descriptions of seasonal points by Bailey and Sonderegger. Vinck's "The Elliptical, Circular and Linear Dials" detailing of the mathematical foundation of a whole class of azimuthal sundials with examples of strange looking sundials by Sawyer, Olgesby, Gianni, Massé, Sassenburg, Sonderegger, and Rouxel.
Fred Sawyer III has a number of articles within the Analemmatic SourceBook, including "Of Analemmas, Mean Time and the Analemmatic Sundial", "Foster's Diametrical Sundial", and many more.
The Analemmatic Sundial SourceBook provides a rich historical and mathematical account of the Analemmatic Sundial and its modern derivatives. Order yours today by clicking here: NASS Publications Order Form
Open the "Read More" to see the detailed contents
You can now reach the NASS website using
On some web browsers you'll get a notice using http://sundials.org that this is not a secure site. For example on Firefox you get the outline of a lock with a red line through it, and on Microsoft Explore (Windows 10) you'll get a not saying "Not secure sundials.ort" followed by "Your connection to this site isn't secure."
All of that is solved. Switch your web browser link to https://sundials.org All of the menu items and pages remain the same.
Your NASS webmaster.
Google Arts and Culture offers you to take a virtual tour of the 13th century observatory Jantar Mantar in Delhi. At the opening view (see the website link below), the Google tour explains: "Innovations in architectural astronomy: The Jantar Mantar Obervatory, Delhi's outdoor astronomical observatory is the earliest of five observatories built by Sawai Jai Singh II across India. It is dominated by a huge sundial and houses other innovative instruments that help plot the course of heavenly bodies...."
"The Maharaja designed four similar observatories in Jaipur, Ujjain, Mathura and Varanasi to help and improve upon the studies of space and time. The Jantar Mantar in Jaipur is now the largest among them." Google gives us a glipse of the large equatorial dial of the Man Singh Observatory in Varanasi and then focuses on the four large brick and plaster instruments at Jantar Mantar: the Ram yantra, two circular structures next to each other used to observe celestial objects; the Samrat yantra, one of the largest equatorial dials in the world with stairs leading to the top of the triangular gnomon (looking like stairs to the heavens) and surrounded by a large equatorial band to measure solar time; the Jai Prakash yantra that consist of two elaborate sunken hemispheres so large that there are stairs from the bottom leading between huge longitudinal bands; and the Misra yantra, which is shaped like a heart and is composed of five different sun and alignment instruments to determine the shortest and longest days of the year at the solstices.
Take a personal visit to these historic astronomical and solar instruments at: The Jantar Mantar Observatory - Google Arts & Culture
The National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) is an Italian Government sponsored research and development agency. In 2017 Sara Bollanti and her team at ENEA in Frascati developed a solar compass that "is 100 times more precise than magnetic compasses..." with applications for surveying, civil engineering, and for us, sundial alignment. The heart of the device is a combination of GPS receiver for determining both time and geographic position and a solar collector consisting of a narrow slit and a CMOS image detector. Essentially this is an electronic solar azimuth compass. A smallArduino computer uses the UTC time plus geographic coordinates to compute the local sun azimuth and then compares it to the position of the sun's projection of a slit on a CMOS detector. According to ENEA, the "...electronic solar compass is compact, completely automatic, cheap, and reaches an accuracy better than 1 arcmin. The latter is one of the best currently available values, comparable to those achievable by means of much more expensive and sophisticated devices, like coupled GPS systems (see for example U.S. patent 5,617,317A, 1997) or gyrocompasses. Furthermore, the ENEA compass provides the orientation in a few seconds, a time extremely shorter than that necessary for gyrocompasses."
By 2018 this was tested in Antarctica and now the mathematics has been reduced to fit into your smart phone. In April 2020 the ENEA team announced the developed the smartphone app i called "SunPass". It is currently in beta testing and will soon be available at the Play Store. In basic form, the app allows you to acquire the sun azimuth by pointing toward the shadow of a vertical object such as a building ("shadow method") or the shadow of a vertical pole ("gnomon method"). A more accurate appraoch is to construct a box with a slit on the front and hole on top such that the smartphone can observe the illuminated sun line on the floor of the box ("Slit method"). For the advanced, one can construct a precision holder from a kit that mounts on a tripod.
ENEA's goal of a low cost, simple method of precision alignment is now accessible to all. This new technology implements the mathematics of determining the sun's azimuth in elegant ways. But of course it only works on sunny days.
|Photo Credit: Andrew Thompson|
Archaeologists have found two miniature stone engravings in a cave on the island of Sulawesi in Indonesia. One plaquette appears to be a sunburst, the other an ibex like animal, the anoa. These pocket-sized carvings dating back between 14,000 and 26,000 years. Elsewhere in Sulawesi the oldest cave art dating to 44,000 years ago was recently discovered, dispelling the Euro-centric notion of Pleistocene art.
Examining the incisions cut into the ancient flowstone, the Sunburst hexegon outline was carved starting in the photo from upper left, with continuing connecting lines done clockwise. Then the 7 rays were added. Small traces of a red mineral (perhaps red ochre pigment) exist in some of the sunburst cuts, possibly indicating that the sun was enhanced in a beautiful red color. Before this discovery the oldest known depiction of the sun was from the Nebra sky disk found in Germany and fabricated of metal 3,600 years ago, rivaling Pharaoh Akenaten who built a whole city to the glory of the sun (Aten) 3,365 years ago. These are recent times compared to the sunburst.
The archaeology team was lead by Michelle C. Langley of the Australian Research Centre for Human Evolution, Griffith University, with associates at Arkeologi Nasional (ARKENAS), Jakarta, Balai Arkeologi Sulawesi Selatan and Balai Pelestarian Cagar Budaya in Makassar. They report in Nature Human Behaviour "... the discovery of two small stone ‘plaquettes’ incised with figurative imagery dating to 26–14 ka from Leang Bulu Bettue, Sulawesi. [The pocket-art was discovered in a cave and rockshelter complex of Leang Bulu Bettue (4° 59' 31.18" S, 119° 40' 5.53" E) situated at the foot of a limestone tower in the Maros-Pangkep karst area.] These new findings, together with the recent discovery of rock art dating to at least 40 ka in this same region, overturns the long-held belief that the first H. sapiens of Southeast Asia–Australasia did not create sophisticated art and further cements the importance of this behaviour for our species’ ability to overcome environmental and social challenges."
The artefacts reported here are currently curated at the Australian Research Centre for Human Evolution, Griffith University, Nathan, Australia. They will return to Indonesia at the conclusion of the project where they will be given accession numbers and be curated in Makassar by Balai Arkeologi Sulawesi Selatan.
Read more at:
Several years ago in 2017 archaeologists found a rare hemicyclium sundial. Now another hemicyclium in excellent condition has been unearthed in Turkey's city of Denizli. Celal Şimşek, chief archaeologist at Denizli's Pamukkale University, calls it "unique". A better word is rare. Less than a hundred examples of this type of Hellenistic sundial have survived. It was found in the ancient city of Laodicea about 370 miles south of Istanbul. The sundial seems to have come from the archaeological site of one of the temples. As reported in the Daily Sabah, "Among the rare, largely preserved buildings in the city are the largest ancient stadium in Turkey, a theater and a sacred agora." The hemicyclium of pink marble has an outer edge decorated in foliage while the interior hemisphere has the traditional Greek names of the seasons. Hour lines deliniate the time. Almacantor lines show the solstices and a great circle marks the equinox. In AA Photo of the sundial at right, a needle gnomon has been restored to show how the sundial casts a shadow. Time and season are read at the gnomon shadow's tip.
ADDENDUM FROM SUNDIAL DIGEST - 10 April 2020
I would like to add two arguments to the questions [of the sundial's age] under discussion:
1. Prof. Şimşek said: “On the North Parados passage in the Western Theater, which dates back to the Hellenistic Era, in the ancient city we have found a spherical sundial facing south, which we believe to be 2,020 years old.
This is a kind of conclusion which does not help by dating the dial. A comparison with similar specimens reveals that it was probably done around 200 – 400 CE.
2. “Inscribed on the dial are the Greek word ‘Ksimerini’, or winter on the upper part; ‘Isimerini’, or solstice, which denotes the equality of day and night in the middle; and ‘Terini’, or summer in the bottom.”
I read (ΤΡΟΠH) ΧΕ(Ι)ΜΕΡΙΝH / IΣΗΜΕΡΙΝH / (ΤΡΟΠH) ΘΕΡΙΝH.
These are the names of the solstices and the equinoxes. What is conspicuous is the missing of I in χειμερινή (it should be written with diacritic signs). That is another strong argument that it was done in the Roman era.
With best wishes
Here in Great Falls Virginia on the day of the Spring Equinox, March 19th, it's a rainy day. Perhaps that helps us want to stay inside with all of the travel and meetings restrictions imposed because of the Covid-19 virus. However, astronomical events aren't deferred because of human and biological issues. Late today the sun crosses the celestial equator and heralds in Spring. You can observe this event remotely thanks to Lowell Observatory in Arizona. Lowell Observatory will begin Live Streaming the event starting at 9pm EDT. "The spring equinox in 2020 occurs on Thursday, March 19 at 8:49pm MST/PDT (3:49am GMT), when the Earth's axis is exactly perpendicular to an imaginary line drawn between the Earth and Sun. On the equinox, the Sun rises due east, and it sets due west, no matter where you are on the Earth."