Moon over wherever

Winter Moonrise, Half Dome, Yosemite

Winter Moonrise, Half Dome, Yosemite
Canon EOS-1Ds Mark III
1/6 second
F/11.0
ISO 100
188 mm

Often, including a rising or setting moon will turn an ordinary landscape into something special. Of course, like most things worth doing, moon photography adds a couple of layers of complication: First, there’s the matter of getting there at the right time, with the moon in the right place (it does little good to arrive as the moon rises if it’s skewed 90 degrees from the scene you came to photograph); and once you have everything lined up, you still have to contend with the almost always tricky exposure issues.

A little lunar geometry (you can skip this section of you’re more interested in “how” than “why”)

Many factors, some within our control, some completely beyond our control, determine the time, location, and phase of the moon at any time. The factors beyond our control are things like the earth’s rotation and the moon’s orbit, which determine the moon’s phase and its absolute position in the sky. On the other hand, we can control our location, and take the steps necessary to get us in the right place at the right time.

A full moon always rises and sets directly opposite the sun, rising in the east at sunset and setting in the west at sunrise. This actually makes perfect sense when you take a little time to understand the monthly choreography of the earth, moon, and sun. Just as the earth revolves around the sun, the moon revolves around the earth; at any point in this dance, half of the earth is lit (daytime) and half of the earth is dark (nighttime), half of the moon is lit and half of the moon is dark.

What we on earth see as a full moon is simply that one day each month that the moon’s entire lit side faces the earth’s dark side—that is, when the earth is directly between the sun and the moon (picture a beam of light that follows a straight line that starts at the sun, passes through earth, and ends on the moon). On that day only, as the point of your location on earth rotates from day to night, you’ll see the sun disappear in the west and the moon rise in the east. As the earth keeps rotating away from daylight and into night, the full moon rises higher and higher, reaching its highest point around midnight, then dropping as your location rotates back toward the sunlit side (and sunrise).

So then why do we rarely see a full moon rising exactly as the sun sets? That’s because: 1) the point of maximum fullness (when the sun, earth, and moon align perfectly) only happens at one instant each month—at every other instant of each month’s full moon day, the moon is only almost full (but still full enough to appear completely full); and 2) sun/moon rise/set times we see published always assume a flat horizon—if you have mountains between you and the horizon, your view of the actual sun/moon rise/set will be blocked.

Due to its monthly orbit about the earth, each day (or night) the moon rises a little later and gains or loses a little bit of its disk (the farther it has revolved from that sun->earth->moon line, the less of the moon’s lit side we see). So the night after the moon is full, it rises after sunset and is a little less full. The next night it rises a little later still, and is even less full, and so on. Eventually (in a little more than two weeks after it was full) the moon has revolved all the way around the earth until it lies between the earth and sun (now our imaginary line goes sun->moon->earth); all of its sunlit side faces away from the earth and we have a new (invisible) moon.

We call the moon “new” because the night before it disappears into the sun, all that was left of the shrinking moon (that was completely full about two weeks ago) was a small sliver that shined briefly on the eastern horizon just before sunrise, then disappeared as soon as the sky brightened (it’s still up there, but completely overpowered by the sun’s brightness). The next day the moon won’t appear at all because seeing it would require looking directly into the sun; but the following day, there it is, this time as a thin sliver on the western horizon immediately after sunset (again, it was up there most of the day, we just can’t see it until the sun sets and the sky darkens). This brand new crescent slips below the horizon shortly after it appears. And for the next two-plus weeks it will rise a little later, and grow a little larger, each night, until it’s full again and rising at sunset. Cycle complete.

If we do the math (this won’t be on the test), we can infer that if the moon takes 29.5 days to complete its cycle (from full to new and back to full), and there are 24 hours in a day, the moon must be rising about 50 minutes later each day (29.5/24=48.8). This rough approximation varies with many factors; for simplicity I usually round it to an hour when I do rough calculations in my head. And I always rely on much more precise software or astronomical charts for my critical calculations.

Locating the moon

Those who don’t do a lot of moon photography are amazed at how much the moon shifts above the landscape throughout the year—you can sight a full moon rising between Half Dome and El Capitan one month, and a few months later it’ll be rising above Leaning Tower (far to the south). Fortunately, like many things in nature that appear random to the uninformed, there is actually nothing random about the moon’s location once you take the time to figure it out.

If the idea of figuring anything saps the pleasure from your photography (or sends you into a panic), you’ll be happy to know that sometimes it’s enough to simply know that the moon will be rising in the east a little before sunset (this info is available in many places, in many forms, but the most complete source I’ve found is the US Naval Observatory website). Armed with that knowledge, you can go out to a location with a view of the western horizon, wait for the moon to appear, and start shooting.

On the other hand, juxtaposing the moon with a specific landmark requires more planning. And because its position is so not random, many others have done the heavy lifting for the rest of us. There are far too many moon phase/position resources to name even a small percentage of them, so rather than even try, I’ll just give you a couple of techniques, and the tools that enable them:

  • My old fashioned way (old trick for an old dog): I figured out my technique for locating the moon long before computer software and smartphone apps took away most of the effort. Nevertheless, I continue to do it this way because I’ve already done all the hard work (figuring out how to do it), and I can do it in the field, with zero connectivity (no wifi or cell signal required). After relying for years on a the US Naval Observatory website for the info I need (moon phase and moon/sun rise, set, altitude, and azimuth), I now get all the pertinent data from my Focalware iPhone app (I never said I’m opposed to new technology), plugging it into my National Geographic Topo! (that’s NG’s exclamation point, not mine) mapping software (discontinued) to plot the direction of the moon’s rise/set. To determine when the moon will appear above (or disappear behind) the surrounding terrain, I plug distance and elevation information from Topo! into the trigonometric functions of my HP 11C scientific calculator (originally an actual calculator, but now also an iPhone 11C emulation app) to compute the elevation in of my horizon.
  • Software (the better way for 99.999 percent of you): The Photographer’s Ephemeris (a free computer download or fairly inexpensive smartphone app) is the most complete solution that I know of (though I’m sure there are others I don’t know of)—I probably would have never taken the time to figure out my technique if TPE had been available. Not only does TPE give you the sun and moon’s location and elevation above the flat horizon, it also figures out the the actual (terrain included) horizon. The downside is that because it uses Google Maps, TPE requires connectivity and is better used in advance of your shoot (usually not a problem). Recent TPE versions also allow you to download the maps to your device for offline access—if I were a TPE user, I’d be doing this before every trip.

Exposure

My rule for photographing a rising/setting full moon is that I must capture detail in the landscape and the moon. If my landscape is black (or just too dark), or my moon is a white disk (or blob), my image has failed. But since the post-sunset landscape is in full shade, and the moon is as bright as a sunlit landscape (because it is a sunlit landscape), the dynamic range of a full moon scene is pretty extreme, often too extreme for a camera to handle with a single click (always my goal).

But here’s the great part—if you figure that the moon rises about an hour later each day, and the full moon rises at sunset, then it stands to reason that the day before it’s full the moon will rise about an hour before the sun sets. Factoring in the terrain on the horizon (and assuming you’re not at the base of a mountain), that means that the day before the moon is full is the best opportunity to photograph a nearly full (say 97%, give or take a percent or two) moon rising in the east above a landscape painted with the warm sunlight of the golden hour. Conversely, if your view is to the west, you can photograph a nearly full moon setting in warm sunrise light the day after it’s full. Either way, the day before or after the full moon gives you everything you need to capture your scene in nice, photographable light that’s still sufficient to hold the moon’s highlights at bay.

I’ve found that if I’m really careful with my exposure, I can usually capture enough foreground and lunar detail until five or ten minutes after sunset. Shooting after sunset usually requires raw capture, then massaging the dark foreground brighter, and bright moon darker, in the raw processor. A graduated neutral density filter can increase this threshold to maybe fifteen or twenty minutes after sunset—after that my foreground is unusably dark (or my moon is recoverably bright).

Another technique that works when the light gets too extreme is a composite—two images, one exposed for the landscape and the other exposed for the moon, combined in Photoshop. In the “Rules According to Gary,” this isn’t cheating if you don’t change the size or position of the moon. (Though it doesn’t break my rules, I no longer do composites because I have this weird compulsion to get everything with one click.)

The final piece of exposure advice I’ll add is to make sure your camera’s blinking highlights (also called highlight alert) are set (as far as I’m concerned, they should be set anyway because I see no downside to highlight alert). The moon is usually so small in your frame that it won’t register in the histogram, which means blinking highlights are usually the only way to know that you’re blowing out the moon. I monitor my highlights closely after each exposure and have found that, when shooting raw (jpeg shooters don’t have as much margin for error), I can usually recover enough detail with an exposure 2/3 to 1 stop brighter than the exposure that first showed blinking.

Just do it

Like most things photographic, don’t expect resounding success the first time you try adding a full moon to your landscape. But each time you go out, not only will you improve, you’ll probably come away with ideas for how to do it differently the next time.

Read more about moon photography

Crescent Moon

Moonlight

4 Comments on “Moon over wherever

  1. Great post Gary. Beautiful shots. I love the fingernail crescent Moon over Half Dome.

    And yes, it’s difficult as H*ll to get a well balanced photo of the Moon and the object. Unfortunately, I ran into this just this past week shooting a shot of the Whatcom County Courthouse and a full moon rising above the spires: http://wp.me/pEP2O-T3

    Also, I find the phone app Sun Surveyor a very valuable tool. Moreso than TPE as it has a bad flaw: it doesn’t give the trajectory (which is valuable to know in the mountains). Knowing the trajectory as it rises above the horizon will help you position yourself even better.

  2. Gary,
    Love your work!
    Do you use any filters for your nighttime photos?
    Thanks
    Ron

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