Outdoor » Sun Compass/Clock

« Home/Index

Description

I was fascinated with the idea of a Sun Compass/Clock presented here: http://chrismolloy.com/sunclock. The basic principle is that it can help you to accurately calculate either: the current time; or a true north bearing (or any other bearing, by extension); or your current latitude. All that is required is that you know any two of the three, and that you have an accurate Sun Compass/Clock diagram to work from.

This product consists of an acrylic plastic 'holder' that houses a Sun Compass/Clock diagram created for your specific latitude using a small, free-to-use web application. The web application can be used as often as you wish to generate a diagram for any latitude (just in case you want to use your Sun Compass/Clock at another latitude in the future). This product includes a sliding gnomon (shadow stick) that is positioned based on the current date, as per the instructions below. This product also includes a spare gnomon, just in case you lose the first one.

Want this product customised/personalised? what you have in mind, and I'll see what I can come up with (it's one major advantage of going with a laser-cut solution!)

Please feel free to before you buy if you have any questions. Buy now from my Ponoko Showroom »

Product Options

Want this product customised/personalised? what you have in mind, and I'll see what I can come up with (it's one major advantage of going with a laser-cut solution!)

Please feel free to before you buy if you have any questions. Buy now from my Ponoko Showroom »

Assembly Instructions

To assemble your Sun Compass/Clock, begin by stripping the protective sticky paper from all the parts. Assemble the gnomon (shadow stick) by slotting the base of the tall, thin stick into the rounded base. These should fit snugly, but not require any force to join. If they are too tight, use some fine sand-paper to reduce the nodes inside each slot.

To complete the set up of the Sun Compass/Clock you will need to install and run a small, free-to-use web application that will allow you to generate a Sun Compass/Clock diagram for your specific latitude, and then to print it at a size compatible with the holder. Once you have a print-out, you need to cut it out, secure it in holder (e.g. with rubber bands) and insert the gnomon into the sliding slot.

Sun Compass/Clock Generator

Sun Compass/Clock Generator: 'open' (as opposed to 'save') this link.

The Sun Compass/Clock diagram is generated using a small Java Web Start application. All the files you require will be downloaded automatically from Sun Microsystems and/or this web site. The application was built using Java version 1.6.0 (jdk1.6.0_07), so if your JVM is out-of-date, it will be updated from Sun the first time you use this application. All this downloading only happens the first time you run the application - after that the only downloading that happens is the retrieval of any future updates to the 'Sun Compass/Clock' application that I might periodically release. Once you have downloaded the application it can be used whilst you are off-line - see the Java Web Start documentation for guidance.

To get the application, 'open' (as opposed to 'save') this link: Sun Compass/Clock Generator. You will be prompted to allow the application access to your printer (so it can print you out a Sun Compass/Clock diagram). I'm not sure what will happen if you decline this request, but assuming you can still run the application, you could try printing a screen-shot instead of using the in-built Print function. N.B.: the Java Web Start security model is extremely strict and it is nigh impossible for this application to do anything untoward once it is on your computer. Ultimately, however, you have to be satisfied that content from this web site is not likely to be malicious. Also note that you do not need to 'register', or enter any personal information, to use this application.

Once the Sun Compass/Clock Generator is running, use the 'Display' -> 'Latitude...' menu option to enter your latitude. Use the 'File' -> 'Page Setup...' menu option to allow your printer to print an image at least 180mm [7.1"] wide/high (by reducing the page margins to 10mm [0.4"]).

Once printed, cut along all the red lines (including those in the centre of the diagram) and install the diagram in the holder (between the two plastic layers) with all the slots aligned (plastic and paper). The 'tail' of the gnomon fits into the slot and slides forwards/backwards. The rounded base plate ('crossbar') of the gnomon works in conjunction with the date ring.

Usage Instructions

The '10 Bushcraft Books' links here, here and here explain how to use a Sun Compass/Clock to determine the current time/latitude/bearing to true north. What follows is a brief explanation of my version of the Sun Compass/Clock (see image 4).

    Key:
  1. Sun line for specified latitude
  2. "Latitude shown"
  3. Time lines - in hour intervals
  4. Time lines - in 15-minute intervals
  5. Compass lines - in 5° intervals

You need to hold your Sun Compass/Clock perfectly level and in a place where the sun will fall on it for the duration of what you are using it for. Slide the gnomon forward/backward until the 'crossbar' crosses the date ring at today's date (the photos above show the gnomon aligned with January 6th). To use it as a clock, orientate it to true north. To use it as a compass, orientate it so that the current sun time matches the time on the Sun Compass/Clock.

Time Corrections

Several time correction factors can be applied to help to increase the accuracy of what the Sun Compass/Clock tells you to sub-minute precision. The last two include tables which can be printed out and kept with your Sun Compass/Clock.