Sun compasses
Solar compasses are essentially inverted sundials: A sundial shows the solar time, provided it is properly oriented. A solar compass helps you find your bearings if you know the solar time. There are many types of solar compasses. Nous en décrivons plusieurs ici (cliquez sur les images pour en savoir plus) : Viking sun […]
Howard or Bagnold? Comparing sun compasses
Both are WWII sun compasses, but they differ on several points: Howard Compass Bagnold Compass Preparation Build paper discs for time and place Read the sun’s azimuth from tables Time reference Can work either on standard time, or solar time Designed to work in solar time (see note) Utilisation Hand held or secured […]
Howard Pattern Sun Compass
Because of its longevity, the Howard compass was produced in large quantities—and continued to be produced until recently. It is therefore relatively easy to find at garage sales or flea markets. I found one at Bricasciences, the annual scientific instruments fair. It consists of a disk graduated from 0 to 360 degrees counterclockwise. The 0 […]
Bagnold Compass
Bagnold compass (Imperial Wars Museun) During World War II, the Long Range Desert Group (LRDG) distinguished itself through daring commando operations carried out across vast desert expanses. The LRDG’s ability to navigate the desert with precision was a key factor in its success. However, in these regions, there are large iron deposits that cause compass […]
Viking Sun Compass
The Vikings faced a particular problem: the journey from Norway to Iceland, and then on to Greenland, took place at a constant latitude, very close to the Arctic Circle (shown in red in the image). However, these voyages took place mainly in the summer, as winter weather conditions were extremely harsh. It was therefore almost […]
The Saint Hilaire Trick
The Saint Hilaire method is remarkably effective. One of its most intriguing aspects is that the calculations are not based on the estimated position, but on a (not too) different position: the selected position. The selected position is chosen close to the estimated position to simplify the calculations. In fact, the estimated position is rarely […]
Backstaff (Davis Quadrant) : a video
I have long wanted to make my own Backstaff. I finally did ! Here are two short videos to show how a Davis Quarter works : Part 1 : principle Part 2 : in use More to come on the subject! https://youtu.be/7jiWUQfnQgQhttps://youtu.be/MRSzK_cVcOA For more information on astronomical navigation throughout the centuries: My lecture for the […]
Article in L’Astronomie!
My latest article, “Daylight Saving Time, Standard Time, and Solar Time,” appeared in the October issue of L’Astronomie magazine! t also features the Papophoplon in real-world use. Head to the newsstands!
The Equinox Video
https://youtu.be/iD8ibJ3zYs4 A simple joy: watch how the shadow moves throughout this equinox day! As predicted by theory, the bottom of the shadow (the shadow cast by the tip of the gnomon) moves in a straight line. This only happens during the equinoxes. See you for the spring equinox! Bonus: If you want to verify the […]
Conference: Astronomical Navigation through the Centuries
I delivered this lecture on September 24, 2026, in the community hall in La Rochegiron (04150). Knowing one’s position at sea is a matter of survival. Out on the open sea, when the coast is out of sight, the only visible landmarks are the stars. What instruments and techniques have been used over the centuries […]
Total solar eclipse of Augusr 12, seen from Ferrol (Spain)
Watch the sun’s reflection fade into the ocean and listen to the sounds around you… https://youtu.be/CykS2jQcM-Q On August 12, Le Cadranier de Fontvieille traveled to Spain to witness the total solar eclipse. Ferrol is a port in Galicia, near La Coruña (about 60 kilometers from Santiago de Compostela). The eclipse was total there for just […]
Silver Medal for the Papophoplon!
I’m very happy about this award at the Concours Lépine! The Papophoplon’s goal is to breathe new life into sundials and, in doing so, to: Showcase their magnificent scientific, artistic, and historical heritage (40,000 sundials installed just in France), and Get our brains working! The Papophoplon’s three uses: Private use: a gift for yourself […]
The Papophoplon in 1 minute
Just a short presentation (you scroll, you choose): Brief recap: Sundials indicate true solar time, which is different from our watches’ time (Standard time). There are three adjustements from one to the other: Mean time Standard time (the same hour for an entire territory) and Daylight saving Time The Papophoplon gives you those 3 […]
Who reads panels?
In La Ciotat, on the port, there is a nice sundial: It is an equatorial sundial, dating from 1873 called the barometer sundial, because it includes a barometer. Like most sundials, it shows solar time, which is not the same as the time on our watches (standard time).To enable it to be used for telling […]
Make your own Papophoplon!
The customisable Papophoplon You can now make your own Papophoplon. Enter your longitude and time zone offset from Coordinated Universal Time (UTC) to find out the solar time for every day of the year! You can use it in two different ways: 1. Play online Tick the ‘Vector’ box to display a button that allows […]
I am entering the 2026 Lépine Competition!
Since 1901, the Lépine Competition has been showcasing passionate inventors, both amateur and professional, who devise ingenious solutions to improve our daily lives. It does not necessarily reward “technological revolutions”, but rather: simple and brilliant ideas objects that are immediately useful innovations that are often very practical That is what makes it so interesting: transforming […]
How to use the back of the Papophoplon?
The back of the Papophoplon is only needed if you’re using the instrument somewhere other than the location for which it was designed. It features a map of France, which shows the additional adjustment required depending on your location. In practice, find your location on the map and read the adjustment in minutes at the […]
A scientific method for finding noon at 2 pm!
Stop looking for noon at 2 pm — just find it! Note for non-French speakers: there is an expression in French about : “Looking for noon at 2 pm”. If you are looking for noon at 2 pm, it means you are complicating things unecessarily : looking for things that do not exist, or not […]
When does solar time fall on a round number?
We know that solar time differs from legal time and that this difference varies throughout the year. Are there any days when the difference is a round number: zero, one hour, or two hours? If so, where and when? The Papophoplon (see description here: theory and practice) highlights the days when the red curve (the […]
World Sundial Day: it was on March 20th, 2026!
World Sundial Day was on 20 March 2026, the day of the equinox. For the second year running, it provided the occasion for amajor online conference, attended by around a hundredsundial enthusiasts from all over the world. Around fifteen speakers took to the stage, and their presentations sparked fascinating questions and discussions. It was a […]
A new sundial in La Farlède !
Going from this: a marble slab at the stonemason’s… To this : As you can see in the GIF above, the virtual Papophoplon (see here) shows 11 o’clock in solar time and the dial shows 11 o’clock. It’s very accurate! NB: I had to make a GIF because even with contrast on my smartphone set […]
The impact of obliquity on the equation of time
Here is a Geogebra animation that allows you to visualise the equation of time due to obliquity (the tilt of the Earth on its axis of rotation).Select the day of the year and view the difference between solar time and legal time.Please note: only obliquity is simulated here.
Virtual Papophoplon
If you do not have a physical papophoplon, you can still find out the difference between legal time (the time on your watch) and solar time.To do this, simply enter your longitude below: Please note that this tool works for locations on UTC+1. For a universal electronic Papophoplon, plese see here. Chargement… Adjustment Seconds Minutes […]
Papophoplon: Why does it work? (The theory)
In this article, we explain the three adjustments made by the Papophoplon. 1. Summer time or winter time? The first difference between solar time and your watch comes from summer or winter time. The sun does not know that you set your watch forward one hour in summer. Nor does it know that the legal […]
Papophoplon: How does it work? (in practice)
How to convert solar time to clock time? Frustrated by looking at a sundial and finding that it doesn’t show the same time as your watch? Here’s the solution: the papophoplon allows you to synchronise your watch and sundial (and lots of other things!). How does it work (in practice)? The papophoplon comes in the […]
A sundial in a glass!
https://youtu.be/oUihOOhkaI8 Place the glass flat, with the eyelet facing the Sun. On the side oppposte to the Sun the shadow of the eyelet should fall on the markings on the dial. Turn the glass slightly so that the shadow of the eyelet falls within the column for the month. If it is 1 September, the […]
Le Cadranier – Finance
An independent consultant at your service! After fifteen years of international auditing (in England, France, the United States and Gabon), I founded FinHarmony in 2001 and made it the independent leader in IFRS standards in France, in consulting and training. In 2025, I sold FinHarmony and now offer my experience and expertise to you. More […]
Paticence!
How should the hours be counted?
Depending on the region and culture, the beginning of the day has been defined as the moment when the Sun rises or when it sets. The hours counted from sunrise are called “Babylonian hours“. They were in force among the Chaldeans, Egyptians and Greeks, in particular. The hours counted from sunset are called “Italic hours“. […]
Nova, Supernova, Hypernova, Kilonova: let’s take stock!
As the name suggests, a nova is initially detected as a new star. In reality, it is an existing star, which suddenly becomes much brighter: it becomes visible, whereas it was not visible before. Further study of novas has made it possible to understand that these are always stars at the end of their lives, […]
The equation of time
1. What is daytime? True solar day vs. mean day According to the simplest definition, the day is the period that separates two successive passages of the Sun at the meridian. This is the definition of the “true” day. True solar noon is the moment when the Sun passes the meridian of the place of […]
Astro Compass Mk II
Astronomical compasses were used by both sides during World War II, when other alternatives could not be used. For example, a magnetic compass can be severely disrupted near a large mass of metal (aboard a bomber, or at the head of a column of tanks, for example). Or you can’t signal yourself by radio when […]
Finding the North without a Compass (1/5) – With a stick (and the day)
Finding the North without a Compass Plant a stick (gnomon) on flat ground. Locate the length of the shade throughout the day (by placing a small pebble on the tip of the shade, or by planting a small stick). It is important to start these readings in the morning, so that you have the morning […]
Finding the North without a Compass (2/5) – With a stick (and 30 minutes)
Plant a vertical stick in flat ground (gnomon). Locate the end of the shadow (by placing a pebble, or by planting another stick). Wait about half an hour. The sun has moved, and so has the shadow. Locate the new location of the shadow end. Draw a straight line between these two locations: this is […]
Finding North without a Compass (3/5) – With a regular watch
With a regular watch (graduated from 1 to 12) Orient the watch so that the small hand is pointing in the direction of the Sun, while keeping the watch flat. To improve the quality of the reading, you can plant a stick in the ground and orient the watch so that the shadow of the […]
Finding the North without a compass (4/5) – With the 24-hour hand of a “pilot’s” watch
Some watches have a 24-hour hand. It is normally used by travelers to keep a reference time, which is why it is often found on “pilot’s” watches. This allows them to set their watch to local time – and even several times, if they travel from one country to another without returning home. They keep […]
Finding the North without a compass (5/5) – With a double sundial
To use a sun compass you must know the time, and therefore you must have a watch or a radio. So how do you find the North with a sundial, without knowing the time? The answer is clever: you need to have two, of different types. From the book Les Cadrans solaires by Denis Savoie […]
Astronomical navigation – GeoGebra animation
Instructions for use This GeoGebra animation replaces the reduction tables used in astronomical navigation. Step 1: Enter your estimated position Use the first two sliders: Latitude (degrees, minutes and negative, if southern hemisphere), and Longitude (degrees, minutes and negative, if east of Greenwich). => Point A moves on the Earth’s sphere to represent the estimated […]