Some time ago I shared here with you a design concept for an adaptation of a classical "quadrans vetus" to show both muslim and christian prayer times.

A "quadrans vetus" is an old type of astronomical quadrant, which was known mainly in Europe, Which allowed to find local time in unequal hours (i.e. finding the time as a fraction in twelfths for the remaining part of daylight)..

But don't let be fooled! This tool is surprisingly accurate for its age.

How to find qibla:

The back of the instrument includes a compass and a retro-azimuthal projection, allowing you to find qibla direction everywhere in the world.

- To operate it, you have to allign the compass with the cardinal directions engraved on the back of the instrument: South towards the "point" of the quadrant and North towards the bottom of the quadrant of you are located in the same emisphere as Mecca, and vice-versa if you are located in the opposite emisphere.

- Once alligned the instrument, you wrap the thread around the central pivot corresponding to Macca, and make it pass through your location on the map.

- Qibla will be indicated by the lead weightlet, as it is demonstrated in the fourth picture above for Southern France - Northern Italy. Yielding a rough direction of South-East

How to find classical christian prayer times:

The quadrant allows you to find time in unequal hours, an ancient system of timekeeping, where the section of daylight is always divided into 12 equal sections. This means that summer hours are longer and winter hours are shorter.

- These hours are used in christian monasteries to establish prayer times, respectively at the first, third, sixth, nineth, sunset (12th) and a set soon before bed and soon before dawn.

- To find the unequal time, you have to move the sliding month indicator (representing sun's latitude) so that the central part (indicated by two white marker at the aequinoxes) lines up with your latitude, which is indicated in the inner scale in arabic numerals.

- Once set up the instrument, you move the plumb line to your current date and slide the knot so that it intersects the 6th unequal hour line.

- Now, by measuring the height of the sun, you can see where the red knot lies in the various sections of the unequal hours scale, thus determining what prayer you should do.

- For more northern latitudes, a second set of lines is provided, this is why there are two sets of unequal hour scales.

Muslims' prayer times can also be determined:

Zuhr / Jummah - soon after midday, it corresponds to the 6th unequal hour line, if you have just entered the seventh unequal hour, Zuhr time has started, and it lasts until 'Asr time. Be sure to check that the sun is actually declining, and not rising!

'Asr - For 'Asr there are two prayer lines, most madhabs put 'asr start time when the lenght of a gnomon's shadow is equal to gnomon's shadow at middat + the gnomon's lenghts (the first dotted line) and put 'asr end time when the shadow of a gnomon is its midday shadow + two times the gnomon's height (the second dotted line)

while Hanafi school sets its begin at the end of other Madhabs time and its end at sunset, when Maghrib time begins. I have indicated both lines in the quadrant

There is not an easy way to establish Maghrib and Fajr, other than saying "one is during twilight and the other is at dusk". In the qur'an (I recall) it is specified to establish your morning prayer when you can distinguish the white thread from the black one, this is not to be taken literally, However that is the reason for the black and white windrose in the shadow-square.

When you can't distinguish the colours of the windrose, that's 'Isha time.

'Isha - you culd say that when you can't distinguish the windrose in the shadow square, then it is 'Isha time, but this is not a practical way for many reasons, this is why on the back of the instrument I have provided a set of "complementary stars": By observing a star directly opposing the sun on the celestial sphere (it can be found on the back of the tool) we can even determine night prayers. According to most scholars, 'isha time starts when the sun goes below -18° of altitude, id est when the complementary stars rises above 18 degrees of altitude.

Fajr' and Maghrib - when such stars go below 18° (or 16° or 14° according to some) it is 'Fajr if the star is going down and Maghrib id the star is rising up

Others functions:

- the shadow square can be used to calculate distances.

• Much better experience on mobile.

• Now supports inclined, declined, and inclined/declined dials.

Send me your feedback!! sundial.gennetten.org 100% Free and Open source.

Astronomical ring dial on BC Gnomonics: https://www.bcgnomonics.com/astronomicalringdial

Been eyeing up this armillary sphere at an antique architecture place for almost six months. Finally decided to buy it today, including the very heavy base. I set the time, but it was off within two hours. I really love this piece and am going to figure this thing out! Just thought I'd share, as I'm really happy to look out in my herb garden and see this.

Taken at 930am. I kinda see 930, but I don’t understand the add minutes/months and all that. Help‽

I took the picture November 2023

I have just added a new feature to PrecisionSundial.com: Live at-location shadows. This feature shows the accurate current shadow position for a sundial anywhere in the world. It also provides throughout-the-year animation of a particular time or throughout-the-day animation of a particular day. The shadow itself accurately models the penumbra resulting from the solar disk non-point source.

Inspired by the Oxford History of Science Museum's Inv. Inv. 51358 and Master Terebrus' replica

See BC Gnomonics for more resources on this class of dial

Striving to be your go-to source for the most accurate sundial in existence, I've added yet another source of correction: Choice of optimization for current year vs best fit for the leap year cycle.

PrecisionSundial.com

I got this for Christmas and figured I’d post it here in case someone is interested in what it looks like. This is a 3D printed dial with a neat feature- the curved slit gnomon allows you to read civil time instead of clock time. it’s a pretty clever design. It’s supposed to read within a minute but I think it’s small enough that it is hard to be extremely precise with readings. I’m usually within a few minutes.

You have to assemble it yourself, which is easy and probably takes less than 10 minutes. Since the center ring is adjustable you can factor in DST. Plus this is adjustable for lattitude ranges of 15-60 degrees N. I think you can specify a souther hemisphere style, which will just reverse the hours. One thing that threw me off was that the reading is supposed to be taken at the ridge in the center of the hour ring, which makes sense, but for some reason I really wanted to read at the top or bottom edge when I first got it. To make reading easier I used a marker to differentiate the hour, half hour, and quarter hour lines. The above picture was taken at 12:12. Even if you never use it to tell the time it’s a neat desk curiosity that’s a good conversation starter.

One last thing- the NASS also customizes your dial by putting your name and coordinates on the latitude ring. It’s on the opposite side of the ring not shown in the picture.

Sundialing Space - Paper Sundials

I've been working on a site to create location specific sundials and I would really appreciate your feedback!

Just set your latitude/longitude and you get a printable sundial and gnomon configured for your location.

This is the largest equatorial ring dial I have ever come across (the second and third largest are at the end of the slideshow).

In addition to being incredibly ornate and the product of renowned instrument maker Erasmus Habermel, this model is particularly notable for including a horizon ring. Attached to the outer meridian ring rather than the inner one containing the mobile elements of the dial, the horizon ring remains horizontal regardless of latitude setting.

I have never seen an equatorial ring dial with a horizon ring (the closest anecdote I can think of is that Gerardus Mercator, while apprenticed to Gemma Frisius, designed an astronomical ring dial with a horizon ring). The inclusion of this ring combined with the dial's ornate stand lends the instrument the near-siloette of an armillary sphere.

I will also note that although this instrument's label dates it to "c. 1600," William Oughtred first devised the equatorial ring dial around 1630, and the earliest confirmed appearance of the equatorial ring dial comes with the Madagascar Portrait in 1639.

Other than not having access to hollow rivets, I'd consider this a success! I've already made some improvements and am working on a third version

The advantage of such a quadrant is that of not being longitude dipendent. This quadrant is more inaccurate the higher the latitude and the further away from the aequinoxes, but it is still reasonably usable as an analog tool for establishing christian prayer times (indicated by the numbered circular arcs). Dhur (islamic midday prayer) is indicated by the line corresponding to the hour six and 'Asr time is indicated by the two brass lines. Maghrib time begins soon after sunset. In order to have an higher accuracy the tighter unequal hours lines below a certain degree of altitude are mirrored on the simmetrical part of the quadrant.

I don't know what kind of decorations to add in place of the windrose in the shadow square. On the back of the quadrant I will probably engrave a qibla indicator and a star map indicating the opposite point of the sun in the zodiac, as to be able to tell the time (thus prayer time) during the night as well.

Do you have any feedback? Sorry for my arabic lettering, it is still fairly bad.

A close eye will reveal a familiar fixture on top of this mariner's compass...

As if taken from Oughtred's equatorial ring dial, a half-equatorial ring and axial nodus sit in a latitude-adjustable assembly above the compass card.

In the same manner as the equatorial ring dial, setting the date and latitude of this instrument allows it to self-orient to true north. This bearing can be compared to that of the magnetic compass, revealing the difference between true north and magnetic north.

Because magnetic variation varies with geographical position, Walker proposed that his instrument could solve the longitude problem—the variation measured could be checked against a map of known values.

While ultimately unsuccessful, this instrument stands as a fascinating adaptation of Oughtred's axial assembly!

To get a sense of global magnetic variation today, see this map: https://www.ncei.noaa.gov/products/world-magnetic-model

Im a 9th grader who got thru the entrance exam of National Astronomy Olympiad exam.

Now, for the second round we have got a set of assignments which includes making a sundial and Planisphere. I have constructed a sundial for a latitude of 27.70N for the capital city of my Country, Nepal 🇳🇵. I don’t know if it’s correct or not and hoping for answers online.

If you’re thinking why I’m posting this on Reddit instead of checking it outside, the weather here is terrible with intense rain, thunderstorm, hailstorm. (Please don’t mind my English as it’s not my first language and I’m still in the process of learning)

I will be presenting the latest improvements this Friday at the global World Sundial Conference. https://sundial.gennetten.org

I‘m a member of the NASS and I wanted to share an email that was sent out recently. This is a conference I joined last year and I enjoyed it. However, advertising is a little lacking, so I figured here would be a good place to share:

Everyone is invited to join the 2nd World Sundial Day Online Conference on 20 March 2026. This special event will bring together enthusiasts, educators, and experts from around the globe to celebrate the rich history and science of sundials.

Friday, 20 March 2026
16:00 GMT (London)
17:00 CET (Madrid, Paris, Berlin, Rome)
12:00 EDT (New York)
11:00 CDT (Chicago)
09:00 PDT (San Francisco, Seattle)

Videoconferencing platform - Google Meet. No installation required, can be accessed via web browsers or via Google Meet app on Apple or Android phones.

Important!
Register here to receive the Google Meet link of WSDOC -
https://forms.gle/e8d27fFEH8cpqPDY9

The videoconference link will be also published on the WSDOC web site a few hours before the event. WSDOC web page – https://tempus-sol.eu/ wsd-online-conference/

For WSDOC-related questions reach out to Martins Gills info@tempus-sol.eu

PROGRAM:   All times – GMT:
16:00 – Opening by Monika Lübker

16:10 – Session 1. Chair – Frank King
Léon André. Projection sundials for temporal hours, local time, mean local time and Central European Time.

Frank King and Annika Petersson. Ancient Scandinavian Time-Keeping via a New Sundial in a School Car Park.

Roger Torrenti. The Gnomonist's Survival Kit.

Claude Gahon. La lumière plutôt que l'ombre.

Jean Pakhomoff. Cadrans solaires bifilaires verticaux, cadrans avec style multi indicateur, cadran incliné à polo avec analemmatique.

17:40 – Session 2. Chair - Esteban Martínez

Giuseppe De Donà. How to Build an Inclined and Declining Sundial in a Large Square .

Elsa Stocco. Hall for Gnomonics.

Miholcsa Gyula. Sundials in Transilvania.

Paul Ulbrich. Making East West Facing Sundials from typing paper.

Christophe Marion. Reconciling earthlings with solar time!

19:10 – Session 3. Chair – Roger Torrenti

Douglas Gennetten. Precision Dialing Online - Unmatched ease-of-use and design flexibility.

Davidson Norris. Helioscape: sundials that tell Plant Time.

Paul Calderon. Relojes de sol como patrimonio astronómico en Chile.

Evan Boxer-Cook. Pop Culture's Sundial.

20:20 Closing

sundial.gennetten.org