Sunrise/Sunset Position

Calculating exactly where the sun will rise is not always easy. Here are a few methods.

The obvious way is to watch the day before and mark where the camera and actor should be. But if it is cloudy or that can't be done, other methods are necessary.

If you are 100 % confident of your compass and are sure there are no local magnetic variations / deviations where you are planning to shoot, trust your compass and use your computer sun position print out. I would suggest this method only after a lot of practice and successful predictions.

True north can be found with a transit as surveyors do using the north star. The north star circles around the north celestial pole by 54 minutes, less than a degree. The method is described in most books on surveying and the Sokkia Celestial Observation Handbook and Ephemeris. Available from Forestry Suppliers #37489 or any surveying supplier.

Using a map table and landmarks to line up land marks with a map to find exact true north. Trust this method only after practice. (See Map Table)

Using sunset azimuth the day before to find true north. If the horizon can't be seen you can calculate the angle of travel with the horizon and use this. A sun position measurement and computer print out will also find true north. (See General Sun Information). If you have local compass magnetic deviation but none on your own body, the errors will be constant in the same position. You can measure sunset and turn around where the computer says sunrise should be with accuracy.

If you are too late after sunrise to check the day before you can accurately predict where it rose by checking the angle it is rising to the horizon with a clinometer. You can plot a few positions and find that angle from your computer sun position program. Don't attempt this when the sun is more than 3 hours above the horizon. (See General Sun Information)

Gyro compasses will find true north, but are still heavy and not yet very available.

GPS receivers can find directions if used carefully. PRACTICE FIRST.

The position of the moon by computer is also a way to align a transit to true north.

Make a Monograph to better understand the sun's travel. (See "Monograph for Sun Position")

© Copyright 1999-2004 Ron Dexter. All Rights Reserved.