I was attending a workshop at Zion in early November.  The workshop was mostly classroom work but we had time to shoot sunrise and sunset.  A group of us decided to photograph the Court of the Patriarchs for sunrise and I persuaded them to arrive a good hour before sunrise while it was still dark and the stars were out. Photographing starry skies is challenging and if you can do it, it can be very rewarding.

We arrived earlier than planned and had plenty of time to get down to the river's edge and get set up.  We walked out onto a gravel bar to get a better angle but left our camera bags on the bank - away from the mud.

To really photograph the night sky you need a specially modified digital camera.  The modification essentially consists of removing the filter from in front of the sensor.  This allows the infrared light to pass through and the infrared spectrum in the night sky is rich with detail and color.  But failing that, you can still get some good night images.

I guess you could say that night sky photography comes in two flavors - star trails and no star trails.  I prefer the no star trails flavor myself.  There's a trick to getting no star trails though.  You have to have a shutter speed that is fast enough to stop the stars in their tracks.  Generally speaking, any exposure longer than 30 seconds will start to show noticeable star trails.  But this depends on the focal length of your lens. The longer the focal length, the shorter the exposure.  That's because you've zoomed in on the stars so any little movement will be much more apparent.  Makes sense.

So how do you know how long of an exposure you can get away with for a given focal length.  There's a simple formula you can use.  The number of seconds is 600 / focal length.  So if your focal length is 20 you can get away with a 30 second exposure (600/20).  But if your focal length is 100 you have to settle for a 6 second exposure (600/100).  Many of us shoot a 24mm lens so the exposure for that is 25 seconds.  Remember, that you need to use the effective focal length of the lens.  So if you're not shooting with a full frame sensor you need to multiply the focal length by whatever factor of your sensor - usually 1.5 or 1.6.

The rest of the story is to get as much light through your lens as possible at whatever shutter speed you determined.  Here's where fast lenses earn their keep.  You'll want to shoot with a wide open lens. Then adjust ISO to get a decent exposure.  Decent in this situation means a histogram that is stacked up on the left (shadow) but that still shows something of the foreground and definitely the stars.  There are two remaining things to think about - depth of field and noise.  With any lens wide open your depth of field will be limited.  The longer the lens the more limited it will be.  But even with a wide angle lens you won't want elements just inches away from the camera.  So select compositions where the foreground is out there a ways.  Noise is the other concern, especially at high ISOs.  The current crop of full frame sensors are really very excellent at reducing noise at high ISOs.  If you're not fortunate enough to have one of these cameras you'll probably want to use some noise reduction software in the post processing.

Focusing can be a challenge in the dark.  The trick I like to use is to focus on a bright star or if the moon is out that's even better.  Manual focus is the only way  to go because when you recompose your image you don't want your camera to try to refocus.

So now that you're all set up you're ready to compose.  It's nearly impossible to compose in the dark so you'll need to take some test exposures, check the image on the LCD and make adjustments.  You are literally shooting in the dark.  In addition to checking the composition, make sure you zoom in on a star or two to double check your focus - on you LCD that is.

Many photographers like to use a light source to illuminate the foreground.  That can produce some absolutely fantastic results.  If you're interested in this, keep two things in mind.  First, shoot in the dead of night, preferably at least three hours after sunset and before sunrise.  You want the sky to be its absolute darkest.  Second, don't use an LED light source unless you want the object you're illuminating to look icy cold.  Incandescent light sources provide a nice warm color which, when cast against the dark blue sky of night, is very pleasing.

I shot this image with my Canon 1Ds Mark III with the 24-70 f/2.8 lens.  The focal length was 32mm, exposure time was 20 sec and the ISO was 1600.  The image was captured about an hour before dawn so there was enough light from the eastern sky to illuminate the scene.  No artificial light was needed.  If you look near the top of the yellow cottonwood tree you'll see a little speck of white light peeping through the leaves.  This is from climbers bivouacked half way up, probably preparing their breakfast and getting ready to continue their climb.

In the post processing I darkened the sky a little to make the stars stand out more.  I also emphasized the cottonwood.  I strived to add emotional impact through the selection of colors - the blues of the sky and water, the greens of the cottonwoods that hadn't started turning yet and the yellows of the central cottonwood.  The pinnacles themselves are a cool reddish color.  I think the mood is rather exciting and just a bit surprising.  The colors are almost those of daylight even though they are cool but then there's the sky sprinkled with stars.