© Brooke Clarke 2000 - 2013

My Dials
    Campbell Stokes Sunshine Recorder
    Eppley Pyranometer
    Eastern Science Supply Co. Heliostat
    Schmoyer Sunquest Dial
    Direct Reading Equatorial
    Satellite Sun Blockage Ceiling Dial
    Satellite Sun Blockage
    Chinese Sundial & Comapss   
    Indoor analemma - f/100 Lens
    Universal Sun Compass
    To be Added
For Sale
Stained Glass
Home Pages
MyRelated Web Pages


Once I discovered sundials the first thing that I was curious about was how accurate could a dial be.  The answer is that it can be accurate to one second of time if provision is made to customize the dial for each year.  I still have ideas about how to make a dial that would be very accurate by virtue of having a way to set which of the four years in a leap year cycle was the current year.  For example consider a noon mark (a sundial that only tells when it is noon local time).  If instead of showing the mark as a line use circles to represent the image of the Sun at exactly noon.  If some optical system could be used to make the Sun's image very small then maybe the images for different years in a four year cycle could be separated.  One factor to recon with is the insertion of leap seconds.  This is done to keep UTC in line with astronomical events.

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.

My Dials

Campbell Stokes Sunshine Recorder

While not really a sundial, it is very much related to studying the sun.

Campbell Stokes Sunshine Recorder
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 Pyranometer

This 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.

Eppley Pyranometer

Eastern Science Supply Co. Heliostat - coelostat

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.

    Schmoyer Sunquest Dial

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.
Schmoyer Sunquest Dial step 1. of machining

 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.

Spiral Design Direct Reading Equatorial
The black band just above the time scale is the magnet.
Spiral Design Direct Reading Equatorial

Satellite Sun Blockage Ceiling Dial

Ceiling MarksI 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 totally.

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 the ceiling.

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.

29 April 2005 - I have been marking the ceiling at 12 and 1 PST and when PDT started I added the new 12 and kept what's now 1 and 2 PDT.  A couple of observations:
(1) I should have placed the mirror as close to the window as possible to get sun on the mirror for dates closer to winter solstice.  As it is now (27 Apr)  I can no longer mark the 2 PDT spot because the rain gutter is shadowing the mirror.
(2) I should not have used double sided tape to attach the mirror since it can be moved after sitting in the sun because the sun softens the tape/glue.   Also the tilt can be changed enough t move the spot maybe 3 sun diameters.  Better would have been to use an epoxy to attach the mirror and I'm not sure about a preferred tilt or tip angle, but there may be a desirable angle other than just leveling the mirror.
2 May 2005 - By pushing down or lifting up on the wooden window sill it can be deformed enough to move the sun's spot on the ceiling a couple of sun's diameters.  When released it seems to be back to where it started.  But there may be some temperature dependence that would be hard to detect.  In the process of epoxy application  the mirror down, but first have put 3 small pieces of paper putty under mirror and have set the mirror so that at noon PDT the spot is in line with the prior data points.  Tomorrow if it's still in line then I'll add epoxy.

11 May 2005 the sun now is shadowed by the rain gutter.  Should have placed the mirror as close as possible to the window to get some more days.  The Sun does shine on the mirror earlier than noon.
4 Oct 05 Blockage

4 Oct '05 Sattelite blockage.  Correlation with signal strength numbers was execllent.  The blockage area was drawn about 6 months ago. 

The line at the bottom was drawn at 1:00 PST and now it's 6 months later so it's on the wrong side of the Analemma  .  The Sun crosses this line on 4 Oct '05 at 1:38 PDT.

10 Dec 2005 - Problems with marking the ceiling in December at 12:00:00 PST are rain or cloudy days result in no mark and when it's sunny the Sun is low and into the trees.  This causes the spot of light on the ceiling to be an image of the trees rather than of the sun, not so easy to fit onto the 3x5 card with nested ellipses.


Dent's Dipleidoscope

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

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 Lens

I 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.

Pelorus (Wiki)

This has an appearance similar to the Abrams Universal Sun Compass SC-1.
This one was made by Dietz.  When zero degrees is sighted on the North Star then the degree wheel can act like a compass.  Wiki calls it a "dumb compass".

Dietz Pelorus
Dietz Pelorus

Abrams (aka U.S. Army) Universal Sun Compass SC-1

Abrams U.S. Army Universal Sun Compass SC-1

To be Added

Prototype for 8.5" by 11" flat paper dial

Ring Dial

Combined 2-types of dial that is North finding

Universal Dial

Combined magnetic compass and simple dial

My accurate design Noon Mark with both PST and DST (1 week overlap) - back board 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 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
MapBlast -
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 -

For Sale

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 SundialsRenaissance 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
UltraPro -
The Event Inventor -
Useful Inventions for Hiking - including using your hands as a Sundial by Karen Robinson

Other Dials

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 Glass

There are a number of ways that stained glass can be incorporated into a dial:
Some Stained Glass photos -


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

Home Pages

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 -

Heliograph (Mk. V)

Combines a mirror with Morse code to send messages.  Started about 1865.  There are two types, one is a hand held instrument like used in the survival kit on a life boat.  The other is a typically military communication device used to send Morse messages between stations that are miles apart.  The key elements are a mirror or mirrors that can be positioned so as to aim the reflected sun light where you want it and a way to tilt the mirror for sending Morse code.

The signaling mirror that's part of the equipment on a life boat has the front surface all mirror and on the back there's a small centered mirror surrounded with printed instructions.  In the center there's a "+" shaped hole in the mirror's silvering.  When the mirror is held in front of the face you can see distant objects through the "+" hole and also you can see a "+" shaped image of the sun on your face.  When you align the sun's image as seen in the back side mirror with the "+" shaped hole the front of the mirror is reflecting the sun at the center of the "+" opening.  This mirror can be tipped to send morse messages, although not as convenient as a normal Morse type key.

It may be possible to modernize the heliograph by using electronics to read the light flashes, and to control the sending mirror.

The Heliotrope is very similar except it has no provision for sending Morse code.  Used in surveying to mark a distant point

The Heliograph -
The Royal Signals .. Heliograph -
Heliography -

Heliostat Patents

This is a moving mirror that de-spins the Earth to allow observing the Sun.
250672 Heliostat, L.D. McIntosh, Dec 13 1881, 353/3 - Looks like a microscope.
273752 (Solar) Microscope, L.D. McIntosh, Mar 13 1883, 359/382; 359/384 -
333769 Heliostat, A.M. Mayer, Jan 5 1886, 353/3 -
1938003 Self Adjusting sunlit Reflector, J.M. Arthuys et al, Dec 5 1933, 353/3; 160/5; 250/203.4 - Polar shaft w/mirror at 45 degrees to shaft CL.
1976428 Self Regulating Heliostat, J.M. Arthuys, et al, Oct 9 1934, 353/3 -
2135997 Automatic Heliostat, J.M. Arthuys, et al,Nov 8 1938, 353/3; 126/605 -
2458654 System for and Method of Utilizing Microwave Radiation from the Sun, G.C. Southworth (Bell Labs), Jan 11 1949, 348/162; 342/7; 343/760; 343/765; 343/912
1850774 Direction Finder, P. Schwerin, Mar 2 1932, 33/361; 324/250; 331/182; 340/870.44 - magnetic
1904059 Method and Apparatus for Testing Incandescent Lamps and Similar Articles, W.L. Kubach, Apr 18 1933,
2151549 Aircraft Landing Equipment, H.I. Becker (GE), Mar 21 1939,
2204052 directive Signaling, W. Van B. Roberts (RCA), Jun 11 1940,
2231929 Tridimensional Radio Direction Indicator, J. Lyman, Feb 18 1941,
2234323 Radiant Energy Receiving Device, I. Wolff (RCA), Mar 11 1941,
2319195 Image Reproducer, G.A.Morton (RCA), May 11 1943, 348/164; 250/330; 313/112; 313/355; 313/465; 315/11 - IR
2712772 Self Regulating Automatic Heliostat reflecting Mirror Device, F Trombe, Jly 12 1955,
1938003 see above
1976428 see above
2022144 Light Conditioning and Destribution System, A. McLean (Communication Patents), Nov 26 1935 -
2135997 see above
2656764 Mount and Means for Supporting and Orienting Optical devices, M.B. Johnson, Oct 27 1953, -

3924954 Heliograph, J-C Decret et al, Dec 9 1975, - Campbell-Stokes, Jordan, Marvin Foster in Guide of Instruments and Meteoroligical Observations 2nd Ed OMM No 8 TP. Supplement No 5 Aug 1965.


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.

My Related Web Pages

Time & Frequency
Sundial patents
Navigation - Time and position are directly related
Optical Spectrum Analyzers


Brooke's Home , page

Page created 30 Jan. 2000.