In the past the USNO observed stars with the Photographic Zenith
Tube to determine what time it was. This system had an
absolute accuracy in the millisecond range. Now they use
Very Long Baseline Interferometry (VLBI) to set the time.
This is done on a world wide basis. Use the link to
the IERS on my Time & Frequency
page for more informatio.
My web page on Stellar Time
considers how accurate you can get using stars.
Land surveyors have used the Sun to determine a North - South
bearing with great accuracy. To do this they need to know
their location and very accurate time. This requires special
adapters on the surveyor's transit. This process could be
used in reverse to determine time.
Pinhole Astrophotography - For the best resolution a pinhole
of diameter d (mm) should be 745*(d^2) mm away from the image.
Campbell Stokes Sunshine Recorder
While not really a sundial, it is very much related to studying the sun.
There is a setting for latitude so the main axis is aligned to the celestial north pole.
A special paper is installed in a slot depending on the season of the year.
The sun burns a trace when it's shining.
Eppley PyranometerThis is an instrument with pretty much the same function as the above Campbell Stokes Sunshine Recorder except it makes the measurement electrically.
While not really a sundial, it is very much related to studying the sun.
Eastern Science Supply Co. Heliostat - coelostat
A clockwork turns the lower mirror to follow the sun.
The rotation axis needs to be set for the local latitude and aimed at the North celestial pole.
This can be done by using a leveled surface and leveling the base by means of the level vials then rotating the unit when set to the correct time until the sun points along the rotation axis.
See Heliostat patents below.
If you have any information on this ESSCO unit please contact me.
I first learned about this dial from Fig 4.4 in the book "Sundials: Their Theory and Construction" by Albert Waugh, 1973. But they were no longer in production.
After he died his daughter offered the casting kit and I got one.
Today there's an entry on the Precision Sundials web page for the Schmoyer.
I shipped a couple of parts to Tony Moss in England for machining.
This is the most critical step.
Direct Reading Equatorial
Spiral Design Inc., Boulder, Colorado made this dial. It can be adjusted for latitude using the clamp bolt to rotate the main support ring and adjusted for longitude (and DST) by moving the calibrated time scale (magnetically attached). There are two Equation of Time Corrected Gnomons. They serve the same purpose as turning the Schmoyer Gnomon, but that means you need to store the one that's not being used.
The short pin on the lower gnomon support rod needs to be turned so it points to the Sun to get the correct Equation of Time (Wiki) correction.
The black band just above the time scale is the magnet.
Satellite Sun Blockage Ceiling Dial
use Starband for my internet connection. It's a two way
satellite based system. At my house there's an orange peel
type offset fed dish that has both a receiver and a
transmitter. It's very similar to the Ku band receive only
satellite TV receiver dish and this idea would work for them also.
Using a 3'x5" card with an elicipse
about the same size as the sun's image with a hole in the center
to mark the sun's position on the ceiling. And the Starband
signal strength window displayed on my computer screen. When
the signal gets down to 6.0 (it's normally between 7 and 8.5) one
mark is made. Then another at 5.0. A yellow
highlighter is used to emphasize the range between 6.0 and
5.0. When the signal gets down to 4.8 my system shuts down
I don't yet understand why the 4 Oct
2004 marks don't line up with the March 2005 marks.
(it very well have been that the mirror got moved!)
All the sun blockage marks are around
12:45 PST in the spring and 1:40 PDT in the fall (and to the left
of them is a mark made at 1:00:00. I have added dates to the
left of the 1:00:00 line to make them easier to read. For a
reason that I don't understand my camera does not want to focus on
On 4 March 2005 I drew the sun's
outline to give the diagram some scale. Note that the sun
moves it's own diameter in about 2 minutes.
The dipleidoscope was developed in the 19th century to use mirrors and a clear glass plate to determine noon to within 10-15 seconds. Fred Sawyer's daughter made one out of mirrors as a science project. Fred also has an original Dent's Dipleidoscope in his collection. The June 1993 issue of the Bulletin of the British Sundial Society (93.2) includes an article "High Noon" by Charles Aked on the theory of the dipleidoscope.
The UK patent dated A.D. 1843 No. 9793 was filed by Mackenzie Blozam and titled "Meridian Instruments."
A how to make article appeared in the book "The Amateur Scientist", printed in New York in 1960 or so. The purpose was to determine the orbital period of Earth Satellites on successive rotations by noting the time they passed through a fixed azimuth. The main components are (1) a horizontal first surface mirror, (2) a second first surface mirror with it's rear edge raised so that the angle between the mirror faces is say 140 degrees, (3) an optical flat that's been silvered to about 38% of the light is reflected. This glass flat if placed over the two mirrors so when viewed from the side the three components form a triangle.
When a heavenly object if viewed there will appear two images, one from the silvered glass plate and the other is causes by a double reflection by means of both mirrors. As the azimuth of the object changes the two images will merge and at one point will be coincident, this is the time to mark.
The Amateur Scientist dipleidoscope is intended for viewing with the eye. The Dent patent covers both naked eye units and one with a built in telescope.
Chinese Sundial & Compass
based on the I Ching and used for classical compass school Feng Shui
Indoor analemma on floor (brass tacks) with Aluminum plate in skylight with hole - F/100 LensI used this in a noon mark made by drilling a hole in an aluminum plate located at the bottom of a south facing sky light. To determine the hole size I first tried various holes in cardboard. A starting point is that a pin hole camera would have an "f" number of 100. That is the hole diameter would be 1/100 the focal length (or distance to the dial). If the hole is smaller the image is dimmer, as the hole gets larger the sun's image gets more fuzzy. The image was an ellipse since it was projected on a wood floor. I had a stiff piece of 3x5" paper with a number of ellipsis and a small hole in the center. Using a watch synchronized to WWV and the beeper turned on, I tracked the sun's image and stopped when the watch sounded. Then just drive in a brass tack.
This took many years to get all the noon marks.
Note (AFAICR) the tack for noon on the same date in different years was typically more than a brass tacks head diameter away from prior years although closer to prior years than different dates. Caused by the leap year cycle that lasts four years.
To be Added
Prototype for 8.5" by 11" flat paper dial
Combined 2-types of dial that is North finding
Combined magnetic compass and simple dial
My accurate design Noon Mark with both PST and DST (1 week overlap)- adjusted to be South facing
British Sundial Society (BSS)- Publications - How to join your national sundial society -
Epact - electronic catalogue of medieval and renaissance scientific instruments
Fer de Vries (Dutch Sundial Society) - THE reference page although some are Dutch - Mayura Draw - DeltaCad - for files conversion
Greenwich 2000 -
Long Now Foundation - 10,000-year Clock - New Scientist article -
Martian sundial designed for 2001 space mission -
Museum of the History of Science, Oxford -
DOC - National Oceanic and Atmospheric Administration (NOAA) - Sunrise/Noon/Sunset Calculator -
North American Sundial Society (NASS)-
Scientific Instrument Society - to bring together people with a specialist interest in scientific instruments, ranging from precious antiques to electronic devices only recently out of production.
Society for Interdisciplinary Studies - G.F. Dodwell study of gnomons?
Sundial Mailing List - Sundial Mailing list Graphics page -
Univ of Tokyo -Cosmology -
University of Wisconsin - River Falls - Richard D. Swensen Sundial - Design -
Analemma Applet -
Analemma - an explanation & sun graph to plot yours
Arnold Moy's HP48 Home Page - Calculator program to show the Sun's illumination of the Earth
Astronomical programs at the Oakland.edu site
Astroware 1 CD-ROM -
Cadastral Survey -
Dialist's Companion - Dialing computer program
Disney World FL Sundial - SunPath Designs -
Florida Solar Energy Center -
Frequently Asked Questions about Calendars -
LJ Coletti - Web calculators
Mapmaker - World Map showing the Day-Night terminator -
Microwave Telemetry - uses sunrise and sunset time to calculate position of bird or fish
AstronomyAnswerBook: The Position of the Sun
Richard B. Langley - Geodesy and Geomatics Engineering page -
Sky & Telescope's - Astronomical Software Menu -
Solar Calculator - Sundial Generator -
Sun API - by David Pratten - does a lot of calculations relating to the Sun's postion
Sundial Generator - by Jordan Schwartz
US Census Bureau - Tiger Mapping Service -
USNO Astronomical Applications Department - Earth's Seasons -
Virtual Visit - software - Shadows 1.5 -
Analemmic-Equatorial Sundials - by Pete Swanstrom - heliochronometer
Ames Instrument Company - Universal Ring Dial -
Antique PocketSun Dials -
Artisan Industrials - Spectra Sundial - A prismatic windowsill sundial
Blades of Tara - has many dials -
BSS Sundial designers and makers -
Cast Bronze Armillary Sphere Sundial -
Celestaire - Pelorus Compass - both old and new - Books on sundials, longitude & navigation -
Classic Science - recreations of classic instruments $400 to $3000 range
Colonial Brass Company -
Connoisseur Sundials -
Courtyard Sundials, UK -
Daniel Oberti Garden Oriented Artifacts - Sun dials & Moon disks -
Digital Sundial - - Patents -
Flowton Dials - both dials and instruments for making dials
GEOMARK(TM) Personal Location Marker -
Gunning - heliochronometer
Helios - Elegant German dials
Kate Pond - Odyssey Of Light Is Installed - crossing beams of light from cylindrical mirrors
Kenneth Lynch & Sons' - #1505 & #2599 -
Merlin Design - etchers in brass
Metalwork at Penobscot Creet Farm - Large Custom Sundials -
Moonstick - slide rule that can calculate the moon phase for any date, past (8000 years), present, or future (8000 years).
Morrison Associates - has lost the gnomon pattern for the Schmoyer sundial - but did pay for a replacement patern.
Personal Astrolabe -
Precision Sundials - Renaissance Focusing Sundial - heliochronometer
Real Goods - Solar energy supplies also in Mendocino county
Saunders and Cooke Antique Re-Creations -
SON Manufacturing Co. - Compass Dial -
Stanley London - a California company offering reproductions
Sundial Fair - shops with common advertising
Sundials - made to measure -
Sunpath Designs -
SUNWATCH UHRI - nice Swiss design
Tony Moss - Lindisun Sundials
Ulysse Nardin watches - Trilogy - Astrolabium - astrolabe in a wrist watch -
Wenger Sundial -
Wind & Weather - carries many nice sun dials (in Mendocino county like me) -photo of Dual Water Tank store in Mendocino - moved to Fort Bragg
Rayzist - photo resist for abrasive blast
The Event Inventor -
Useful Inventions for Hiking - including using your hands as a Sundial by Karen Robinson
Cambridgeshire sundial trail - Royal Greenwich Observatory Sundial -
in The Netherlands -
Sundial pendants -
Compass with pocket string sundial -
Hewlett-Packard PA-7300LC microprocessor -
Chinese Sundial -
Sundial List Server Image Page - Equatorial Heliochronometer by John Carmichael -
Die HALBE - ACHT - Sonnenuhr - a new type of dial?
Stained GlassThere are a number of ways that stained glass can be incorporated into a dial:Some Stained Glass photos -
- The glass might be used as a surface treatment for a conventional type of dial
- The glass would form a translucent dial face where the style was on the outside of a building
- The glass would form an image that would be projected onto a special area on a floor or wall or using a mirror to almost anywhere.
Information Leaflet No. 71: `The Tercentenary Sundial -
Information Leaflet No. 75: `The longitude of Greenwich -
The Invention of the Chronometer - US PTO article in bottom 1/3 of page
Sun Compass - used in WWII Africa SC-1 manual front cover,
Evolution of the Sextant -
'Magic' Viking Sunstone Just Natural Crystal - calcite crystal, called an Icelandic spar
Angelo Brazzi -
Atmospheric Optics - Rainbows, etc.
Bernard Droege -
Daniel Roth - links - German home page - sponser of the mailing list
Deux cadrans analemmatiques à heure légale - analemmatic sundials for legal hours - Bonjour et bienvenue sur ce site - with some pages in English
Electric Astrolabe - this could get habit forming - The Astrolabe - Astrolabe Links and References - links-
Fred Sawyer's list of links -
Gordon T. Uber Sundial page
Grzechnik Sundial page -
Hours and Unequal Hours by Nicholas Whyte
Internet Sundial web Ring - just press "next" at the bottom of each page
Jack Aubert - Sundial Theory -
Jim Lattis -
Jordan Schwartz -
Olbers-Planetarium Bremen - German site moon dial?
Robert Terwilliger - Sundials - Randolph AFB Sundial - Bob is restoring the AFB dial
Sundial site of Frans Maes -
Sundial Sculptures of Stone and Brass - by John L. Carmichael Jr. At what point does a sundial become a heliochronometer?
UAI - Sundails Section - Italy
Sundials, Their Theory and Construction by Albert E. Waugh, Dover Publications, ISBN 0-486-22947-5 - This is the classic sundial theory & construction book.
A Choice of Sundials by Winthrop W. Dolan, Stephen Greene Press, ISBN 0-8289-0210-0
Sundials Their Construction and Use by R. Newton Mayall & Margaret W. Mayall, Sky Publishing Corp., ISBN 0-933346-71-9
Sundials How to Know, Use, and Make Them by R. Newton Mayall & Margaret W. Mayall, Sky Publishing Corp., Lib of Congress # 73-76242
Astronomical Formulae for Calculators by Jean Meeus, Willmann-Bell, Inc. (math books) ISBN 0-943396-09-3
Practical Astronomy with your Calculator by Peter Duffett-Smith, Cambridge University Press, ISBN 0 521 28411 2
Astronomy with your Personal Computer by Peter Duffett-Smith ,Cambridge University Press, ISBN 0 521 31976 5
Mathematical Astronomy Morsels -
Making A Clock-Accurate Sundial Customized to Your Location by Sam Muller
BSS book list -
There are three kinds of patents. Those that start with US are classical inventions, USPP is a Patented Plant, and USD is a Design patent.
I have put the patents on a separate Sundial Patents page. There are a lot more patents that I am trying to get organized. The IBM patent server changed to Delphion and now requires registration. Although the free basic service can be used it prevents direct links to patents. The USPTO has improved and has many of the older patents as TIF images and there is a free viewer to see them and they can be directly linked. In the future that's the way to go.
Need to update to Google patents.
This is the science of designing sundials and relates to the gnomon which is the part of the sundial that casts the shadow.
Time & Frequency
Navigation - Time and position are directly related
Optical Spectrum Analyzers
Page created 30 Jan. 2000.