It's always something when shooting time lapse...always.
As I sat at my computer yesterday, everything looked to be converging beautifully: The forecast called for clear skies, the nearly new moon wouldn't rise until after 4:00 the following morning, assuring a dark shooting environment and most exciting of all, the Earth was passing through the orbital path of the Swift-Tuttle Comet, whose debris field would pummel the atmosphere later that night resulting in the Perseid meteor shower. I even had a rural shoot location along the shore of Crystal Lake near Wautoma, Wisconsin, far away from the light polluted skies above Madison. I spent much of the day preparing for what I felt certain would be the best clip I'd ever shot. I'd sit down to write this entry, then triumphantly upload my dazzling video of the cosmic light show I'd so brilliantly captured and top it off with some compelling Carl Sagan quote about stardust or the solar system.
But this is time lapse, and there's always something. There was indeed a convergence last night...of unwelcome clouds and some rather poor choices on my part.
When I arrived at Crystal Lake I was met by our friend Ann who, together with the Davis and Riley families own the lakeside home where I would be shooting. The house is perched high above the lake on a wooded, sandy terrace. Down slope a pier extends out into the lake, which is where I decided to set up my camera. The problem with my choice was that the only unobstructed view of the sky I could get was east - southeast. The meteor shower was going to be "easy to see," the meteorologists had assured viewers earlier that day, by simply "looking to the northern sky." It would seem that I had overlooked a pretty important requirement for this shoot: I wasn't facing the right way. Nonetheless, with a wide 24mm lens I could aim high and was confident that I'd capture enough of the northeastern sky to get some comets. And that's precisely what I should have done.
Two things happened around 9:30 last night: The linear form of the Milky Way began to materialize in the southern sky, and I learned that my 3 year-old's knack for being easily distracted and veering off task must come from me. It was the Milky Way after all, far too tempting to resist. The comets would surely venture into the southern sky. I decided (based on absolutely no astronomy knowledge or training) that they would. I promptly rotated my tripod head directly to the south...180 degrees from where I should have been shooting.
With everything logistically in place (or out of place depending on how you looked at it) I had to turn my attention to the technical challenges of the shoot. I shot with a Canon 24mm f/1.4L II lens, which I opened to f/1.6. Before beginning to shoot, I pressed the depth of field button then rotated the lens, detaching it. By doing this, it became a fixed aperture lens, insuring that I would avoid flicker- the distracting staccato effect that can turn a great time lapse clip into a mediocre one, or worse. There was an additional problem to contend with during a shoot this long: Dew drops condensing on the glass. Last year I shot for three hours in the Nicolet National Forest only to discover that the lens had completely fogged over early in the sequence. Not this time. Enter battery powered fans, Gaffer’s tape, and hand warmers.
Dew is basically water that condenses on objects that are cooler than the Dew Point temperature. Tonight the Dew Point was around 60 degrees which meant if the temperature dropped close to that (cooling my lens glass in the process) water would form on it. I needed to keep my glass warm. There are a number of ways to do this, but I chose the cheapest (and arguably least attractive) method: I used Gaffer’s tape to attach a series of hand warmers to the outside of the lens then wrapped the whole concoction in a piece of neoprene I’d cut from one of my old wetsuits. These warmers are cheap and last up to 7 hours. I also set up a battery powered fan below my camera-a method that has proven effective for keeping insects away from the lens.
With fan whirling, the settings locked in, and viewfinder covered, I began the sequence. I shot at f/1.6, ISO 3200, with a 20 second exposure time. Because I wanted to use some of the images as stills, I followed the “500 Rule” of star photography: Take 500 and divide it by the focal length of the lens I was using, in this case, 24mm. I divided 500 by 24 which gets me a number just shy of 21. If my shutter was open for more than 21 seconds, the stars would begin showing up as trails, an effect I didn't want. I used a 30 second interval: 2 shots per minute; 120 shots per hour. Since the result of this whole endeavor will be an HD video clip played back at approximately 30 frames per second, every hour I shoot, I’ll get about 4 seconds of video. That's a lot of time and planning to get 20-25 second clip.
Once the camera was going, there was no point in staying with it so I wandered around the property a bit, shooting a few stills with another camera, sat with Ann for a long overdue catch-up session, and even grabbed a 45 minute nap. I periodically walked back to the lake edge to make sure the camera was still firing and I began to notice a disturbing lack of stars in the southern sky. I knew that my camera would pick up stars that I couldn't see, but the northern sky (which I should have been shooting in the first place) was positively crowded with them, brilliantly lit and remarkably defined. The southern sky on the other hand, had an odd yellowish tint that meant something I dreaded: a low bank of clouds had streamed in and was reflecting the tungsten light from the cabin porch lights below, masking the stars in the process. I had chosen exactly the wrong direction to shoot, a sickening realization four hours into the shot on a sleepless night.
But this is time lapse, and there's always something...and sometimes it's interesting. The clouds, which I'd feared would completely obscure the stars and the Milky Way, only did so partially as they raced past, adding a level of depth to the piece. And even hidden behind the clouds, the Great Rift of the Milky Way (the dark seam of dust clouds that run its length) was visible. A few stray meteors did in fact find their way into my scene. I made a lot of mistakes last night, but I still ended up liking the sequence. The next moonless Perseid meteor shower will be in August 2018, so I have plenty of time to make a plan and convince myself to stick to it.