Author Topic: Sundials and their application to Prepping  (Read 7005 times)

Offline iam4liberty

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Sundials and their application to Prepping
« on: February 20, 2017, 12:55:59 PM »
This is a break off thread on one on the use of an ephemeris.  In it we started to talk about the different types of sundials and their usefulness.  It seems best that a more in-depth analysis would fit here so I am opening one up for further discussion.

The sundial is one of our oldest and most important tools.  When most people think of a sundial they think about telling the hour of the day.  This was important as it told us the daylight left for activities but it was only the tip of the iceberg.  A sundial can also tell us the day of the year.  This is important for planning (e.g. when to hunt/fish certain areas and plant crops and for coordinating trade with other groups.  The timing of most religious and civil festivals were also determined by the sundial (though some were lunar based).  The sundial was also the primary tool of navigation.

Therefore it might be useful to understand the different types of sundials and their uses.  Let's start with the most basic of all, the noon mark.

1. Noon Mark

The noon mark is the grand-daddy of them all.  It is simply a North-South line onto which an object casts a shadow.  When the shadow crosses the line, that is solar noon for that location (aka local apparent noon).  For years these lines were incorporated into the architecture of buildings. 

Noon mark example on a building


And it just wasn't large structures.  Every pioneer home would have a noon mark.  And this practice continued right into the nineteen hundreds. Even when clocks were becoming common place, the noon-mark persevered.  People would paint a small circle on a south-facing window so it would cast a shadow on the floor or wall where the line was placed; sometimes drawn/painted but other times by placement of floorboards/tiles.  This noon-mark was what was used to set the clocks daily!

Noon-mark dial for setting the time on watches c1760


Why was the noon mark so important?  It allowed people in a given area to coordinate action.   Say you had people out working in the fields.  They could know when the time of the noon repast was coming and therefore when to go back to the homestead.  In the same manner, those with kitchen responsibilities at the homestead knew when to have the meal ready.  It also was commonly used by scouts as to know when to return to base camp.  The idea being that once noon hit if you turned back you would be able to make camp while there was still light. 

It also allowed people to know when events were happening in a town.  An example would be to know when Sunday services were going to begin.  In fact, it was standard to ring church bells three times a day, once at dawn, once at noon, and once at dusk.  Many churches today continue this practice via clock time at 6 a.m., noon, and 6 p.m.  It is no wonder that some of the most beautiful noon marks are within churches and other cultural institutions like museums.

The Hall of the Sundial at The National Archeological Museum in Naples was designed in the late 18th century by astronomer G.Casella and architect P.Schiantarelli


Of course, sometimes it may have been more prudent to avoid high noon:



The noon mark is also used for celestial navigation of sea, desert, forest, and swamp.  Different versions of taking a 'noon sight' have been used for hundreds of years and is still the basis for navigation today.  In its current form, by knowing when local noon is, a navigator can determine his latitude and longitude from the height of the sun and the time on a chronometer.  This was discussed in more detail in the ephemeris thread so we won't go into details here. 



The noon mark is so ingrained in our psyche that we still break our days in half at noon.  It has been proven a healthy and convenient point of reference for daily activities.  For this reason the noon mark is still as relevant as ever to the homestead.  And it is really easy to add one.  It can be as simple as finding a tall object (e.g. flagpole, telephone pole, antenna) and placing a stone directly North of it.  When the shadow from the pole crosses the stone, it is local noon.  It can be as simple or elaborate as you want to make it, from just a small rock to an ornate slab.




Offline FreeLancer

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Re: Sundials and their application to Prepping
« Reply #1 on: February 20, 2017, 02:40:39 PM »
Cool thread.  Keep it coming.

Offline Cedar

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Re: Sundials and their application to Prepping
« Reply #2 on: February 20, 2017, 07:28:37 PM »
I have never knowingly seen one on a building, but that is pretty cool. At a certain SCA event I went to each year, it was made with a stick and painted rocks on the ground with the time on them. Someday I would like to get one which is on a necklace or a ring.

Cedar

Offline Carl

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Re: Sundials and their application to Prepping
« Reply #3 on: February 21, 2017, 05:38:48 AM »
Fossil Watch company made one long ago,now they are metal,I had one made of stone.

https://www.amazon.com/Fossil-Trend-Antique-Sundial-JR9886/dp/B001TMGC46/ref=cm_cr_arp_d_product_top?ie=UTF8

Offline Ralph

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Re: Sundials and their application to Prepping
« Reply #4 on: February 21, 2017, 10:38:29 AM »
When I first got interested in dials I generated the markings by computer. I tried making them from a few materials, wood being the easiest. Even after many coats of marine varnish the weather eventually got to it. To get a more permanent one I tried making one out of a ceramic floor tile. Although I was finally able to scribe some light lines into it I couldnt get them straight. Finding workable materials that hold up to weather is my problem.
An idea I came up with but havent tried was a simple flat brass plate, the markings being simple drilled holes possibly with small screws in them. No markings or lines, about as simple as it gets. A gnomen (sp- have to look that up), or rather attaching one to the plate may be an issue,
As for noon marks, I remember one dial maker who made their gnomen from 2 parallel plates with a small gap between them. At solar noon you set it up so the sun shone through the gap. A nice idea, a noon mark and a check on your dial's alignment over time. Has anyone tried to make a dial?

Offline Chemsoldier

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Re: Sundials and their application to Prepping
« Reply #5 on: February 21, 2017, 11:24:37 AM »
 :popcorn:

Offline Ralph

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Re: Sundials and their application to Prepping
« Reply #6 on: March 04, 2017, 11:23:24 AM »
They do have sundial rings, I saw one online recently. It has a hole that the sun shines through onto a scale. Here's one that's a pocket dial shaped into a ring- but not a finger ring. I like this one:

https://www.pocket-sundial.com/?gclid=COWSjMC4vdICFU-eGwodgEAGLQ

... and 2 that can be worn:

https://www.amazon.com/Sundial-Ring-Silver-Finish-Size/dp/B008TB3CH0
http://www.shepherdswatch.com/aquitaine-sundial-ring-pendants/

I still like the wrist worn sand filled hourglass :}

Offline mountainmoma

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Re: Sundials and their application to Prepping
« Reply #7 on: March 04, 2017, 11:46:58 AM »
I realy like the ones on buildings. Makes me what to put one on my house !

Offline Cedar

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Re: Sundials and their application to Prepping
« Reply #8 on: March 04, 2017, 12:12:45 PM »
I was just at the gardening center with mom earlier today, getting a present for my brother. I found the sundial aisle.. there are some nice ones out this year. I was looking at a stone-type one.. pretty cool.. and i was so amazed with it, I forgot to look at the price (probably out of my non-existent budget)

Cedar

Offline iam4liberty

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Re: Sundials and their application to Prepping
« Reply #9 on: June 10, 2017, 01:21:30 PM »
When I first got interested in dials I generated the markings by computer. I tried making them from a few materials, wood being the easiest. Even after many coats of marine varnish the weather eventually got to it. To get a more permanent one I tried making one out of a ceramic floor tile. Although I was finally able to scribe some light lines into it I couldnt get them straight. Finding workable materials that hold up to weather is my problem.
An idea I came up with but havent tried was a simple flat brass plate, the markings being simple drilled holes possibly with small screws in them.

That is the problem with Sundials, by design they are exposed to the elements.  Wood ones have to be refinished pretty much every year.  Stone and brass are the two most practical materials.

In honor of the upcoming summer solstice, here is the next one.

2. Height of sun above horizon and shadow length

While the noon mark provided a ready reference for the center of the day, more graduations were needed to help coordinate activities throughout the day.  For many latitudes the height of the sun proved the most practical means.  As the sun proceeds in its path from East to West, it's relative height in the sky over horizon changes.   One outcome of this is that the length of shadows vary as the days go on.  At noon shadows are at their shortest while at the beginning and end of day they are at their longest. 



Within towns a tall structure or pole would be used as a common "shadow stick".  But outside of town, people generally used the length of their own shadows.  This method was even mentioned in the Canterbury Tales by Geoffrey Chaucer written in the late 1300s.  This understanding of how one's shadow varied with time was empirically learned as a person proceeded through life.  And since the absolute height of the sun also varied with season, this acted not only as a clock for during the day but also to note seasons (critical for planning food cycles).



Today we can precisely calculate shadow lengths through mathematics.  Online tools make this easy.  So before going on a hiking trip you can use a simple daily shadow calculator as a backup to your watch: https://planetcalc.com/1875/.  And more sophisticated calculators can be used to calculate shadow lengths for determining best planting areas, where to place solar panels, etc: http://www.findmyshadow.com/.  A similar technique is used by the intelligence community to determine when photographs are taken by using shadow lengths: http://forensicgenealogy.info/blog/working-with-shadows-in-a-photograph/

Net, this ancient technology which links time to shadow length still has many practical uses today.

Offline Carl

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Re: Sundials and their application to Prepping
« Reply #10 on: June 10, 2017, 01:41:14 PM »
Karma Liberty, I like that

Offline bcksknr

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Re: Sundials and their application to Prepping
« Reply #11 on: June 10, 2017, 07:02:40 PM »
     I found an interesting sundial at a large flea market. It is actually a "noon gun". On a dinner plate sized round base is a standard inscribed arc with the hours. There is a standard 'Gnomen" to cast the suns shadow and show the hours. However, there is also a six inch brass cannon mounted on the base, with a magnifying glass mounted above it. When properly oriented, precisely at noon, the magnifying lens focuses on the cannon's touchhole. I've loaded it with a small blackpowder charge and a wad of tissue. At noon (local time) it goes off with a loud report. Fun, but something I'd rather not leave loaded outside, except to demonstrate. Of course, pretty useless if it rains or is cloudy.

Offline Carl

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Re: Sundials and their application to Prepping
« Reply #12 on: June 11, 2017, 04:12:41 AM »
     I found an interesting sundial at a large flea market. It is actually a "noon gun". On a dinner plate sized round base is a standard inscribed arc with the hours. There is a standard 'Gnomen" to cast the suns shadow and show the hours. However, there is also a six inch brass cannon mounted on the base, with a magnifying glass mounted above it. When properly oriented, precisely at noon, the magnifying lens focuses on the cannon's touchhole. I've loaded it with a small blackpowder charge and a wad of tissue. At noon (local time) it goes off with a loud report. Fun, but something I'd rather not leave loaded outside, except to demonstrate. Of course, pretty useless if it rains or is cloudy.


Cool,and very rare ,if origional...an alarm clock.

Offline bcksknr

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Re: Sundials and their application to Prepping
« Reply #13 on: June 11, 2017, 07:19:16 AM »
     While we probably don't have to worry about being late for an appointment after the SHTF, modern folks are so driven by time that if the grid goes down or an EMP fries the digital watches, the ability to even roughly know the time could help ease a least a little of the stress.
     I have a couple of sundials, one is combined with a compass and is a repro. of one found at a Rodger's Rangers barracks.  I also have a mantle clock that keeps very good time and a variety of heirloom pocket watches. I even have one of those "cheap" Scotty pocket watches. Each of my kits has at least one way to tell time. Then there is always the "stick and shadow" method. If it all goes down the toilet, I think it's important to have familiar things to keep as much of a sense of normalcy as possible. It's relatively easy to make a compact sundial that would fit in a match box, coupled with your compass it becomes a "clock". I also have the magnetized needles removed from some cheap compasses, tucked in my wallet and other places. They are light enough to float on a palm full of water. Of course with the right knowledge, you can find north and construct a sun clock with just whats under your feet. 

Offline iam4liberty

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Re: Sundials and their application to Prepping
« Reply #14 on: October 13, 2018, 10:04:23 AM »
Just getting back to this.

3. Horizontal and Vertical Sundials

Once people started regularly using shadow lengths to judge time they noted an interesting fact, the shortest shadow of the day always pointed due North (in the Northern hemisphere).  This was very useful for navigation purposes.  But when combined with another observation it led to an even better way to measure time. 

By this time people were used to measuring time at night by watching the stars circle the northern star.  This star is now Polaris but back then (around 3000 BC) this was the star Thuban.  Watch this video for example of how stars move around the polar star: https://youtu.be/SYcKaBzr87g  As noted in this video this is because the earth rotates and the polar stars reside 'above' the earth's North pole.

So it was only natural to look at the apparent rotation of the shadow around the shadow stick as a basis of time, especially since there seemed to be some connection between the shadow length and the polar stars.  Some cultures even stated that the sun 'bowed in homage' to the polar star.

With sticks pointed directly straight up (i.e. perpendicular to level ground) this was not very successful.  The rate at which the shadows moved around the stick did not do so at an even pace.  Furthermore this varied by location and time of year.  But an almost magical thing happened when the stick was pointed at the polar star; the rotation became very stable!  This video shows visually why this happens: https://www.youtube.com/watch?v=0coseLMOGhA

This resulted in an amazing invention, the horizontal sundial.  By angling the gnomon (stick) of the sundial a more consistent time measurement could be set.  This allowed greater coordination of work across a region.  A community sundial could be set in a marketplace to set time of trade, courts for disputes, religious services, fishing/shipping schedules, etc.  Then homesteads surrounding that area could have their own sundials and coordinate accordingly.  This was very important as city centers became more defensible (e.g. walled) and ingress/egress was limited to specific times. In many ways sundials created the sense of 'community' common around population centers.  Almost every ancient society deployed this technology:

Viking


Greek


Egyptian




By medieval times the same technology was incorporated in a vertical form and even integrated in the key buildings.  The amount of detail which went into them show just how important they were.

Ireland (7th Century AD)


Chantres Cathedral (~1150 AD)


Konark Temple (~1250 AD)


Even today these monumental sundials are still used daily as shown in this video: https://www.youtube.com/watch?v=K9RF9lLBIMs

In modern times the sundial is used as a rallying point to give a sense of "community" such as the recently constructed Perranporth Sundial in Cornwall.

https://www.bordersundials.co.uk/perranporth-sundial-cornwall/
« Last Edit: October 13, 2018, 10:22:34 AM by iam4liberty »

Offline iam4liberty

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Re: Sundials and their application to Prepping
« Reply #15 on: October 13, 2018, 10:07:40 AM »
Deleted double post.

Offline Carl

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Re: Sundials and their application to Prepping
« Reply #16 on: October 13, 2018, 10:11:34 AM »
Very accurate too.

Offline Morning Sunshine

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Re: Sundials and their application to Prepping
« Reply #17 on: October 13, 2018, 10:16:46 AM »
I was just thinking about sundials the other day.  and i have a question

I know that the time of year makes a difference for where the sun is in the sky.  How do sundials work all year round?

Offline iam4liberty

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Re: Sundials and their application to Prepping
« Reply #18 on: October 13, 2018, 10:28:59 AM »
I was just thinking about sundials the other day.  and i have a question

I know that the time of year makes a difference for where the sun is in the sky.  How do sundials work all year round?

Good question.  You anticipated Part 4: The Equation of Time and Analemma.  It will show how the sundials are actually a little off by the change in sun altitude through the seasons.  This will fill in how to make sundial better match 'clock time' and also how a sundial can be used as a calendar to give month and day!

Offline Hurricane

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Re: Sundials and their application to Prepping
« Reply #19 on: October 14, 2018, 07:00:02 AM »


In modern times the sundial is used as a rallying point to give a sense of "community" such as the recently constructed Perranporth Sundial in Cornwall.

https://www.bordersundials.co.uk/perranporth-sundial-cornwall/


This could be how Stonehenge began.

And how to build your own version of it

Offline Redman

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Re: Sundials and their application to Prepping
« Reply #20 on: October 14, 2018, 08:08:24 AM »
Karma Liberty. A very interesting subject.

Offline Carl

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Re: Sundials and their application to Prepping
« Reply #21 on: October 14, 2018, 08:12:02 AM »
But STONEHENGE was a burial site.

Offline Redman

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Re: Sundials and their application to Prepping
« Reply #22 on: October 14, 2018, 08:47:12 AM »
Well you had to know what time to start the funeral.

Offline Ralph

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Re: Sundials and their application to Prepping
« Reply #23 on: October 16, 2018, 10:30:38 AM »
Dr Who built it knowing he'd film an episode there.