Instructables
This is a 15-minute paper sundial in two senses: it takes 15-minutes to make and is labeled to the nearest 15-minutes.  It is made of paper, but I designed the gnomon to have a three-dimensional base for greater stability, tapering to a thin top for better accuracy around noon.

The hard work was my doing the trigonometry for the three-dimensional paper-craft gnomon and writing a perl script that generates a pdf file for a particular location.  But with the script written, you should be able to print out a sundial from the generator on my website and construct it in fifteen minutes.

Ingredients and tools:
  • Two sheets of paper, ideally cardstock or some other heavy stock.
  • Scissors
  • Paper glue (I use Aleene's)
  • Printer
  • Ruler
  • Something pointy, e.g., a pen with no ink or a small screwdriver
  • Computer with internet access, PDF viewer, and printer
The script I used was based loosely on the one in my large patio/driveway analemmatic sundial Instructable.  This is a much simpler project.  The last one I assembled took 12 minutes once I had the design printed out and all the tools in place, and that's counting periodic stops to take photographs.

You can load the PDF file into a vector drawing application like Inkscape and make it fancier.  Just make sure that if you resize the dial, you resize the gnomon (the pointer) in the same proportions.  The script is open source so you can modify it as you see fit.

You can presumably trace the printout on copper sheets to make a fancier dial and gnomon.  I'd love to see it.

This would make a good classroom project at various levels, depending on how deep you get into explaining how it works.

Note: The script currently works for latitudes between 24 degrees (north or south) and 65 degrees (north or south).  (That covers all of the contiguous 48 states in the U.S., much of the populous parts of Canada and Europe, all of South Africa, much of India, etc.)  The limitations are due to the way the gnomon is designed to work both when shadows are short and when they are long, and its having a wider base.
 
Remove these adsRemove these ads by Signing Up
paulolondres2 months ago

98 x 102 cm sattelit dish

2014-09-21 20.41.22.jpg
arpruss (author)  paulolondres2 months ago
Wow!
paulolondres2 months ago

can I resize the clock? I am thinking to use in a

dish satellite

What should I get attention?

arpruss (author)  paulolondres2 months ago
You can load the pdf file into Inkscape or Adobe Illustrator and resize. Just make sure all the parts are resized proportionally.
DUO00371 year ago
Sooooooooo Cool!
stmpspaz2 years ago
Bummer - I wanted to use this at a scout camp this weekend, but the perl file isn't working. I have tried to load the file on my own server using the source code - but can't get it to work there either :(
arpruss (author)  stmpspaz2 years ago
I just went to the link, put in my zip code, changed nothing else, and everything worked. I was using Chrome on WinXP.
arpruss (author) 2 years ago
The equation of time is the difference between apparent solar time and mean solar time. This depends neither on latitude nor longitude I think. There is Ann additional adjustment based longitude difference from the official central longitude of the time zone, but that's taken into account when generating the shoal.
koroliov2 years ago
If I understand it correctly, the equasion of the time does depend on the location. The one calculated by your app dosn't seem to take this into consideration. For example, for Vancouver, B.C., the zero time adjustments (0 min) happen on about Oct. 7 and Nov. 30 only, and not on Apr. 15 and Sep. 1 as the app says. Am I not getting something right?
top.boy3 years ago
i made it,gave the right co-ordinates,made a right gnomon pointed it at north it was 3 it gave 5!
arpruss (author)  top.boy3 years ago
1. Did you check to make sure the gnomon's angle was the same as your latitude after you attached it? A photo directly from the side might help to diagnose this.

2. How did you check for north?
top.boy arpruss3 years ago
1.yes i checked the gnomon right

2.i have a compass
arpruss (author)  top.boy3 years ago
1. Did you correct the compass reading for the magnetic deviation at your location?

2. Did you correct for daylight savings if needed?
top.boy arpruss3 years ago
1.yes

2. i don't have day light saving
Unlike widely believed wisdom, the deviation of the compass reading and the true north is not minute at all, and, instead, may be quite considerable. For example, in Vancouver, B.C.. it is 17 degrees (!) If one uses the compass without the magnetic deviation adjustment, the error in the sundial reading will be more than 1 hour! You can check the deviation for your area at the US National Geophysical Data Centre. Try for your location and you may be surprised:
http://www.ngdc.noaa.gov/geomag-web/#declination
arpruss (author)  top.boy3 years ago
Can you give me your time zone, latitude and longitude (feel free to round off to the nearest half degree for privacy) and I can experiment a little?
dauphin19742 years ago
Here's a picture of the one I built from your directions. I used an over-turned ceramic planter base, with the hours cut using a dremel tool. Then I used a piece of found wire (from a street-sweeper) as the gnomen and glued it to the base using a kneadable putty that was out-door-proof. I used the angle guide and the software to create one for the zip-code of the person I made it for. Nice instructable and nice program. Thanks! -- Dauphin1974
sundial.gif
tankdo2 years ago
well my latitude´s out of your range... but hey, great job anyway!! love sundials
arpruss (author)  tankdo2 years ago
Too far from equator or too close to equator? :-)
tankdo arpruss2 years ago
too close :(
4 degrees aprox
i already have a sundial generated in a website, but you locate the edges of your home and it generates a sundial to put in your window (really nice). but for some reason i like too much this kind of sundials i found them more attractive.
I looked up gnomon on dictionary.com, because it's a new one on me, and I wanted to know how to pronouce it. Apparently, the g is silent and it is pronounced like a Jamacan man saying No man: "No mon. every little ting gonna be alright."
arpruss (author)  shakespeare12123 years ago
Yeah, the g is silent. For a visual pun, you can put a picture of a gnome on the gnomon. Sorry, couldn't resist that.
arpruss (author) 3 years ago
By the way, there is an undocumented feature in the script. When you click on "Go" in the script, you get sent to this very long URL, a part of which says something like "num=roman" or "num=arabic". Change that part of the URL to "num=now", and you might be amused by the result.
change it to cardinal
Now, now, now, now, now, now, now, that was a dirty little secret!
Now....
Creativeman3 years ago
Very cool!
Yet, another question...

Does size matter on this?
Could I size the dial down, let's say 50%.
Would that effect the time?

Could I make one that you could wear around your wrist?
Kinda like a joke...Caveman watch?
arpruss (author)  Greasetattoo3 years ago
If you scale it, just scale both the dial and the gnomon equally. (And of course, don't squeeze it down in one direction and stretch it in the other.) Actually, nothing really bad will happen if you scale the dial and gnomon differently, except that the sizing in the script is designed to work well with the different shadow lengths in summer and winter (if I got the trig right).

Do post a picture if you make a copper one.
Oh, one other thing...

Your link to your script.
http://analemmatic.sf.net/cgi-bin/papercraft.pl
Is bringing me somewhere else.

I had to cut and copy the link in a new browser window.
You may want to fix that!
arpruss (author)  Greasetattoo3 years ago
Just did, thanks for pointing it out.
GREAT!
I do have a piece of copper here.
I may have to give it a try!

Love the sundial generator!
Great job.
arpruss (author) 3 years ago
Unfortunately, horizontal sundials of this design don't work this close to the equator. A different design is needed.
Longitude: -38.522186
Erro: Latitude must be between 24 and 60 degrees (north or south).

And now?
arpruss (author)  Alex Ribeiro3 years ago
What was your latitude?
In google maps: Fortaleza, Brazil -3.718394, -38.543395