It was a grand sight to see, the Milky Way stretching across the sky behind Owachomo Bridge. It was a natural subject for the opening spread of National Geographic’s story Our Vanishing Night in the November issue.
First, let’s get this out of the way. This is a straight shot.
That’s right. No layers in PhotoShop. No multi-image, bracketed-exposure HDR computer magic. No telescope-mounted clock-driven hours-long exposure. At National Geographic we really can’t use all those wonder weapons of the digital era. Readers expect reality and we try to deliver.
This picture just involved a camera on a tripod in front of the right scene. Well, almost. Photographing the Milky Way and not ending up with a big blur requires several elements, one of which has only been available in the past couple of years. Here’s what you need to know.
The Milky Way is out there every night. But you need a really, truly dark sky like what they have at Natural Bridges National Monument in southern Utah. You probably can’t do this picture east of the Mississippi. I scouted this location during the day, looking for the right bridge that faced the right direction and that I could get to in the middle of the night. Oh, and if you want a dark sky you can’t have any moon. That’s part of the next step.
Then you need to know when and where the Milky Way is going to be “up.” It rises and sets just like the Sun and the Moon. To find out when it will be visible, where it will rise and whether or not the moon will be up (not what I wanted) I used a very nice astronomy program called SkyGazer4 from Carina Software. This allowed me to set my location (southern Utah) and then spin the clock to see where the Milky Way would be at any given time. The answer, in this case, was that the southern Milky Way wouldn’t rise until about 2:15 AM.
I needed the southern arm of the galaxy because that is the one that looks towards the center of the galaxy, hence it is much bigger and brighter.
Now here is the real trick. In order for the Milky Way to be sharp in the picture the exposure can’t be any longer than about 90 seconds. (And that’s with a very wide 14mm lens.) Any longer and the stars will start to move so much during the exposure that they will be streaks instead of points of light. In fact, 90 seconds is stretching it. Sixty seconds would be better. So the trick was having a Nikon D3 that would let me shoot at ISO 3200 to ISO 6400 with minimal digital noise. We’ve only had cameras that could begin to do this for the past few years. Right now the D3 (along with the now-available D700) is high ISO champion. And I needed an f2.8 lens that would produce sharp images wide open. Fortunately I had the Nikkor 14-24mm f2.8 lens that is just phenomenal. It has very even illumination and it makes sharp star images right out to the corners. (This is a very, very tough thing for a super wide angle lens to do.) Currently, this about the only lens that available that will do this.
Fortunately, the Milky Way is always the same exposure: 90 seconds, f2.8, ISO 3200 will always get you a nice, bright Milky Way. Or, 60 seconds, f2.8, ISO 5000 will work. Or 30 seconds, f1.4, ISO 1600 works well, too. But note that there are no 14mm f1.4 lenses. There is one 24mm f1.4 lens and it can produce some fine star images, though with somewhat limited performance in the corners. The problem to be solved with that lens is getting it in focus, which is fiendishly difficult at f1.4 in total darkness. It must be absolutely in focus. (Hint: auto focus won’t even come close.)
So by 2:00 AM I’m standing behind my tripod and, just like clockwork, the Milky Way is beginning to rise behind the Owachomo Bridge. It’s just stunning. This spot has been named the International Dark-Sky Association’s first Dark Sky Park and I can see why. My picture is all framed up and my first picture tells me I’ve got the angle and exposure right. (I’ve practiced this stuff before.)
Now I just need two more things. First the Milky Way has to rise high enough in the sky to be dramatic before dawn floods the sky with light. So I figure I’ve got about two and a half hours.
And second, I want to light up the bridge. That’s why I brought along four different flashlights. And that’s why my young friend, a summer ranger at the park has agreed to my crazy idea of coming out here in the middle of the night. While I run the camera and check exposures, he’s over there under the arch, hiding behind some trees, painting the bridge with a flashlight during my 90 second exposure. I tell him when the shutter opens and he starts flashing the light, slowly and evenly, along the length of the arch. Too long in one spot and we would get a hot spot. Not long enough and it was too dark.
So for the next two hours we shot frame after frame, getting better and better at making nicely painted scenes of the arch as the Milky Way slowly moved into a great sweeping angle. It was exciting, being out there in the dead silence of the desert night, seeing our images getting better and better until finally I saw the first signs of blue creeping in from the east. But by then we had it. All in one exposure straight out of the camera. Wow!One last technical tip that you’ll need. The exposures took the requisite 90 seconds. (And I experimented with other exposures and ISO combinations along the way.) But then, I had to turn on High ISO noise reduction. It’s buried down in your camera’s menus somewhere. This is essential. The sensor heats up during long exposures, building up unacceptable levels of noise. So the camera then does a “null” exposure with the shutter closed, to see where the noise is building up, then digitally reverses that exposure and subtracts it from the real exposure. Voila, the noise has been nullified, so to speak. Doing this will slow you down but do not bypass this critical step. All this means you’ll be lucky to do one exposure every five minutes. Use your dark sky time wisely.