Dear Membership, Emergency Sundial
For those of us that cannot do without a sundial for an entire day, here are some instructions for making an emergency sundial. First, we have to establish some measuring tools: Holding out both fists turned palm up and together at eye height, with arms fully stretched. Sight through the crack between the fists on some convenient object edge. Now place the left fist to the right of the right fist, keeping the edge of the right fist aligned with the reference edge. Take a new sight and remember the new spot to align, then move the right fist to the right of the left fist. Continue this, counting the number of fists in a full circle. For me, there are 36 fists in a full circle, so a fist is 10 degrees. Adjust your distance from an object so that it subtends a fist of angle. How many index finger widths does it take to cover that angle. For me, it is 5 index fingers, so an index finger width is 2 degrees. The three fingers of one hand starting from the smallest one make up half a fist, or for me 5 degrees. Secondly, we need to find a level surface. Liquid in a glass, soda bottle or plastic bag can serve as a reference. Thirdly, we need to know East and West: If the sun is fairly far up in the sky, mark the shadow tip of something which is more than a foot high. Perhaps with a coin, or a scratched line or pencil mark. Wait for the shadow to move a few inches. Mark this new point and draw a line between the two marks. A shoelace can be laid out to mark it in an emergency. This is an east-west line that is probably more accurate than an uncorrected compass. Extend it if necessary. Fourthly, we need a North-South line. Marking the spot we want to put a gnomon (x) and using the other shoelace to mark two spots at an equal distance from it on the East-West line, Scribing two arcs from these two points on the side of the East-West line that is on the other side from x and putting the east west shoelace between this last point and X we have our North-South line. If we know the local latitude we can lean up a stick from X, pointing north and set to the latitude angle by our fist and finger method. A good guess will work fairly well. Lastly, we need hour lines: Measure out 15 degree angles from the gnomon, radially, with fists/fingers and mark points for each hour angle. Scribe through them and X or mark the most important one with a shoelace. (You may need to mark this out on something else - Observing something that subtends 15 degrees you can fold a piece of paper so that held to your eye as a triangle it subtends the same object.) If there is a radio available, then a local station can give you a current time to make correction for longitude, etc. If you are there over night, and have had the forethought to put the gnomon so you can sight along it to the north, you can align it with the north pole from the stars, if needed, and then lay out your hour lines again, if needed. If you plan on doing this regularly, you might wish to carry a cord with knots tied at points subtending various angles, perhaps a small telescoping gnomon. A list of latitudes of where you might travel would also be helpful. In a real emergency, knowing that three fists are 2 hours, you can measure the distance from the horizon along an estimated path of the sun and tell how many hours from sunrise, or til sunset. Standing in one place you can measure over from your shadow a fist and a half, to find where it will be in an hour. ( Roughly east) Enjoy! Edley McKnight [43.126N 123.526W]
