This month’s Yosemite Winter Moon photo workshop group got the rare opportunity to photograph a full (or nearly full) moon rising above Half Dome at sunset on three consecutive nights. One reason it’s rare is that, as viewed from Yosemite Valley, the full moon and Half Dome only align in winter. But the real tricky part is making it happen three times when sunset happens at pretty much the same time each evening, but the moon rises about 45 minutes later.
My goal for photographing a rising full moon is to get the moon on the horizon in the window from 15 minutes before to 15 minutes after the “official” (flat horizon) sunset. Earlier and there’s not enough contrast and the moon looks bland; later and there’s too much dynamic range to capture detail in the dark landscape and daylight-bright moon.
The key to making this work starts with understanding that when you see a sunset or moonrise time published for a location, that time is always based on a flat horizon. So unless you’re atop a mountain or on a ship at sea, you’ll probably see the sun disappear behind the terrain in the west before sunset, and you’ll probably need to wait for the moon to rise above the terrain in the east.
Since the sun is at my back when a full moon rises, I’m not too concerned about the precise timing of the sun’s disappearance. But I need to be pretty dead-on for the moon’s arrival. Knowing the moon will rise an 40-60 minutes (or so) later each day, it’s easy to infer that the more days until the full moon, the higher the moon will be at sunset. Sadly, I have no control over the timing of the absolute sunset/moonrise, but I can control the elevation of the horizon, and therefore the moon’s appearance on a given day, by choosing my position relative to the horizon above which the moon will rise.
To make this workshop’s consecutive moonrises work, each evening I picked a view that was farther from Half Dome than the previous evening. On our first evening I chose a spot on the east side of Yosemite Valley; the next evening we were closer to the middle of the valley; on our the third evening our vantage point was near Tunnel View, at the opposite side of Yosemite Valley from Half Dome. The moon rose later above the flat horizon each evening, but by moving farther away, we reduced the distance the moon had to travel before it appeared.
Big moon, small moon
The other thing this little exercise illustrates is how to make the moon big in your frame. Notice that in each image, Half Dome is more or less the same size, but the moon gets progressively bigger. That’s because on any given day, no matter where I am on Earth, the moon is so far away that its apparent size doesn’t change. But the size of earthbound features, like Half Dome, changes a lot with proximity. When I was on Yosemite Valley’s east side for the first moonrise, filling my frame with Half Dome required just a little more than 100mm; the next night I was far enough back to require about 250mm to fill the frame; and on the final night, from eight miles away I needed more than 500mm. And as my focal length increased, so did the moon’s size in my frame.