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.
before telescopes, a quadrant was most definetely one of the most accurate tool for doing science. Its functions span from basic celestial measurement, time calculation, and even sophisticated trigonometrical functions for more advanced models.
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.
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If you are curious, you can find this and other astronomical tools on my etsy shop !