Sky watch: Capturing time with photography

Today is a bit of a milestone for me, as I begin my 20th year of writing "Stargazers." I'm sure that many of my longtime readers will have a hard time believing this, but it's absolutely true. And this realization got me thinking about time.

What is time anyway? Great philosophers and scientists have wrestled with the concept for ages, but in many ways, we're no closer to understanding it. What we have figured out, however, is how to measure it.

Many ways exist to do this; most involve tracking natural cycles. The time it takes the Earth to complete one orbit around the sun we define as one year, and we mark it with a calendar.

Another familiar device we use is a clock, which measures the rotation of the Earth on its own axis. We call this one "day."

could be shared with those who weren't there. And the answer, it turns out, is called photography.

A photograph, after all, is merely a slice of captured time. And if we can record birthdays and the like, then why not the stars?

So here's a project for you to try this week. It doesn't matter what kind of camera you have, as long as you can set it to manual mode (M) and you have a tripod upon which to mount it.

Aim it skyward; attach a normal or wide-angle lens and open the aperture all the way (preferably to f/2.8 or faster); set your ISO to 800, 1600 or higher; focus the lens to infinity (marked by the horizontal figure-eight symbol); and take exposures of up to 30 seconds. Soon, you'll begin to see familiar stars and star patterns in the slice of time that you've captured.

Go to twanight.org, click on "Education" and select "Capture the Cosmos" to read my guide to photographing the heavens. I hope you'll share your shots with me at mammana@skyscapes.com.While this all-too-brief time under the magnificent, starry sky may bring you no closer to understanding just exactly what time is, you'll surely find it humbling to watch just how quickly it seems to pass!