One of the active topics in modern photography is the distinction between “blends” (combining multiple exposures from a single camera viewpoint), and “composites” (which combine unrelated images into a synthetic scene). Both are valid uses of photography, but I prefer to limit my efforts to the former, hoping to reveal some scientific beauty in the result.
In this case the relative motion of the stars is “stacked” (added) from 2,335 10-second exposures. Each frame looks like a normal picture of the sky, but when accumulated creates the star trail effect. The frames were selected from the period after “astronomical twilight” when the sun is more than 18-degrees below the horizon. On this date, official night lasted over six hours, and the star trails cover more than 1/4 of a full circle (and even Polaris shows that it is not exactly on the north celestial pole).
Although it was “night”, it was not completely dark. The moon was up and illuminated the scene until it set around midnight. This allows the foreground to show, including the “sailing stone” with its path on the dry lakebed trailing behind it, a contrast of time scales against the motion of the sky.
A final detail to explain: the streaks below and to the left are the result of trains of Starlink satellites moving across the sky. Dozens of satellites follow each other into and out of the sunlight at their altitude, reflecting it down to our observing position on the playa and creating its own trail on this image.
A sailing stone, the path behind it showing the route it took to get here.
There was a second wide spot in the road at the south end of the playa; we parked and continued our explorations. This time we found stones sitting on the surface of the lakebed. There were not many, and we had to hike a mile or so to find them. Some sat happily contemplating their position in the uniform semi-infinite plane of mud cracks. Others showed a faint trail of disturbed, and now solidified mud, leading to their current position. These were the famous sailing stones!
Yosemite Falls is at a thunderous volume in this season, seeming to pour starlight over the edge of the cliff into the valley. The water continues its downward path via Lower Yosemite Falls, the dim watery glint reflecting a moonless night.
A meteor bright enough to light up the forest flashed through the sky just before the end of this 90-minute exposure. A fireball that left a glowing plasma trail, it is a member of the Lyrid meteor shower, an annual April event. It cuts a chord across the arcs of stars making their daily tour around Polaris.
El Capitan’s immense figure blocks my view of the north star Polaris. I can only guess where it should be based on the time and positions of other stars. A position in an open field in Yosemite Valley allows me to make this composition.
The moonless night meant that the only illumination was by starlight. The park is sufficiently remote to escape the light pollution from large cities, but not enough to avoid airplane traffic. The distinct dotted lines mark the strobe lights of distant flights, unknowingly adding their trails to those of the stars.
Yosemite National Park, 13 April 2002 Pentax 67 w 55mm lens at f/4, 2 hour exposure on Provia 400
I was given a hint that I should consider Yosemite Falls as a startrail target because the trail to it ran along a north-south path. I wasn’t brave enough to hike in the dark, but I did find a vantage point from across the valley that placed Polaris directly above the falls.
The moonless night meant that the only illumination was by starlight. The park is sufficiently remote to escape the light pollution from large cities, but not enough to avoid airplane traffic. To minimize them crossing the view, this exposure was done in the very early morning hours when all the airplanes have found their destinations and the only sound in the air was the distant rushing of water.
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Ah, South Dakota. A transition state between the lush prairies and farmlands to the east, and the arid mountains to the west. A bit of both co-reside in this state, and tonight I find myself in a stretch of farmland where the grass has been harvested into giant tootsie-rolls of hay and left at random locations in the field. The mosquitos are fierce, a sure sign of nearby water sources that feed these fields. I do not have my mosquito suit, having left it at home, the land of ten thousand lakes, certain it would not be needed elsewhere.
But I have found another windmill artifact, this one apparently still serving its original purpose, pumping water from the aquifer below to the surface where it can be put directly to agricultural use. Perhaps the catch trough is the source of some of these mosquitos!
There is no wind to make the carnivores work for their blood meal, they land with impunity on any moist skin, and all of my skin is moist tonight. The temperature is 65 degrees, and the dewpoint is the same!
The windmill is about a quarter mile in from the road. I pull off to the side at the field access, an open gate and a vehicle bridge over the gulley. I don’t dare drive into the field, this is not my domain, but I am willing to lug my equipment into place, taking several trips for the tripods, cameras and batteries (to allow the dew heaters to prevent the lenses fogging).
There was not a whisper of breeze, but whatever wind had previously been blowing had left the windmill blades facing south, a fortuitous placement for my composition. I had long wanted to make a direct superposition of the windmill on the North Star, to have the startrails perfectly circumscribe the fan of blades, and here was my chance! I set up the cameras and was surprised where they had to be placed. After a moment I realized that this was exactly right. At this latitude, Polaris was at 450 elevation, the cameras needed to be very low and aimed high to get the composition and angles to work. Even with my wide-angle lenses, the cameras hugged the ground to get the view I wanted.
On my knees to set the tripods, aim the cameras, set the dew heaters, focus and aperture, I finally opened the shutters. I could relax for a while. The exposure time was going to be 80 minutes, exactly one-eighteenth of a day. I had determined this time by counting the number of blades on the windmill, 18. It was a detail that only a mathematician could appreciate, but I have long had suspicions that there are underlying mathematical principles to the esthetic response. I could indulge my intuition in this farmer’s hayfield.
I looked around at the hayfield and realized that I was now surrounded by a thick fog. I could not see more than a few yards in any direction. So this is what happens when the air temperature falls below the dewpoint! I was well aware of the condensation that happens when a lens, radiating heat into space, drops its temperature: it fogs! And so here was an example of the air itself, not just a glass or metallic object, dropping below the dewpoint. Fog!
I experienced a moment of fear. I was out in the middle of some field, I could not see, and I was not sure where my car, or even the road was. Worse, this would ruin the pictures I was taking. But looking up, the sky above was clear. I was in a circular container of fog with the top still open. I could not see any farmhouse lights, my innate sense of direction is poor, but I had the stars to guide me!
If I was not familiar with the sky I would have remained a little frightened, cocooned by a featureless mist with no pointer back to my home base, the car. Instead, I felt somewhat protected. I couldn’t see the traffic on the road, but then again, they couldn’t see me. Their headlights couldn’t penetrate to my camera setup, and no one would wonder what I was doing in the middle of this field. The sky above was open, and my pictures were progressing just fine.
Knowing that I had been traveling north on the road, with the field on the right, I took the steps west, leaving my cameras behind in the fog, until I encountered the road, then north until I found my parked car. I was back at my base camp. I now had a problem. How do I get back to the cameras when their exposure time was up?
My GPS tracker was the answer. I set a waypoint at my car’s location, and then headed back into the fog with the navigation device to find my cameras, this time by “dead reckoning”. I had only a sense of their direction relative to the car and so I set off hoping to see the silhouette of the windmill in a reasonable range. If I didn’t find it, I could always return to the car by aiming for its waypoint, and try again. The GPS signals have no trouble penetrating fog. Fortunately, I found the cameras on my first foray. In a truly worst case, I would have had to wait til morning for the fog to burn off in order to find them. The exposures would have been long ruined, but I would have recovered my equipment.
With markers at both ends of my route, I could now make my way back and forth through the night, each time wandering a slightly different route, but always ending up on target.
Eventually however, the sky covered up completely and even my guiding stars could not be seen. I’m glad this didn’t happen earlier in the evening, before I had my GPS markers set. I would not have been able to find the car so easily. As silly as it sounds to be lost in a hayfield, it would have been a frightening experience. As I packed up and ferried my gear back to the car, following the GPS breadcrumbs, I contemplated the situation I had encountered. My windmill whiteout was a personal lesson in the loss of orientation that explorers experience when they meet more dangerous whiteout conditions. I would advise modern explorers to bring their GPS units!
“Polar Windmill”, a remarkable confluence of opportunity, weather, and technology. This was the last night sky photograph I took on my Nightscape Odyssey, coming full circle to the first.
Climber Trails Mount Ranier National Park, 19 August 1999 Nikomat with 20mm lens at f/5.6 One-hour exposure on E200 push-processed +2 stops
The skies continued to hold clear, the temperature dropped, and the moon set by midnight, allowing me to compose a view of Polaris directly above the summit of this ancient volcano.
There are a number of interesting light sources in this picture. The startrail arcs are made by a one-hour sweep of the Earth beneath the North Star. The green glow of distant Seattle shows to the northwest, the amber of closer but much smaller towns are northeast, and the sky itself illuminates the snowfields on the mountain. An additional light source can also be found within the snowfields.
As I started this exposure, I could sense a faint glow that seemed to come from the slope of the mountain itself. Training a telescope on the area, I found what might be unseen hikers bearing flashlights searching through the snow. I was impressed that a flashlight could be seen at these distances. Camp Muir, where climbers rest on their way to the summit, was four miles away!
I learned the next day that what I had seen was not just a couple of hikers resetting their tent stakes. They had started their ascent to the summit! In order to reach the top and get back down before the snow gets dangerously soft, they must strike out at about 1:00 A.M. This photo captures their first hour of progress on a beautifully clear and starlit night (click to see full size image).
Banff Poles Tunnel Mountain Campground, Banff Park, Alberta Canada, 17 Aug 1998 10:40pm 20mm f/4 Nikon lens, 1 hour exposure on E200 Ektachrome processed +2 stops (ISO 800)
While camping trips make great venues for photographing the
sky, sometimes it is difficult to get a full view of it. But here is an opening
in the canopy, the lodgepole pines framing the pole star. The camera was aimed
at Polaris, and the shutter opened for an hour. The flickering campfires and
lamps illuminated the boughs of the trees.
A startrail picture like this is a powerful illustration of
the Earth’s motion. The pole star shows almost no motion. The others show
longer arcs the further away, but all of them make an equal arc: a one-hour
exposure cuts 1/24th of a full circle.
