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We’re currently en route to Yosemite National Park in California. It’s a fairly long drive from Colorado, around 1200 miles each way, taking in some amazingly diverse scenery along the route (even when you stick to the major highways). Within the space of 24 hours, we passed from Colorado into Utah, then the next day through the northwest corner of Arizona and into Nevada.

Utah was something of a winter wonderland. It was snowing lightly in Grand Junction, CO as we left Colorado and the same weather continued into Utah, until, with 15 minutes before sunset, the cloud broke. We quickly pulled off I70 at the Cisco turn-off and grabbed a few photographs of the sunset. In the image below, you can see a “sun pillar” caused by the ice crystals in the atmosphere bouncing sunlight directly back at the observer:

San Rafael Ice Pillar

If you’d like to read more about these effects, Atmospheric Optics is a great site, with some wonderful images.

The following morning, we left Green River, UT with freezing fog hanging around town. Trees were coated in hoar frost from the moisture in the air. A short way west of Green River, I70 cuts through the San Rafael Swell. There was still fog hanging around the swell, and snow on the ground:

San Rafael Frost

Headed towards Las Vegas, we passed into Nevada by the early afternoon and decided to stop off at Valley of Fire State Park, a real gift of a place for photographers! Yesterday (Dec 27 2012) was the day before full moon, with the moon rising 15 minutes before sunset – ideal for catching an image with the moon rising through the twilight sky.

Ahead of moonrise, we explored some of the view and vistas of the park. You can really get a sense of how the park got its name from some of the spectacular formations:

Valley of Fire

Moonrise was not to be, with clouds blocking the sky just too long to catch the moon properly balanced against the landscape. However, last light on the Virgin Peaks east of Valley of Fire provided a great finish to the day’s impromptu photo opportunities:

Virgin Peak

Today we’re headed up to just outside Yosemite. Fingers crossed for some great winter weather conditions in the park once we arrive!

Here’s a quick insight into some recent usage patterns we’ve seen across all versions of TPE (Desktop, iOS, Android).

The graph below shows the number of calls to GeoNames web services made by TPE users. These calls are made, for example, when you search for a new location, move the map pin to a new location, or move the secondary map pin. At these times, we call to GeoNames to determine things like place names, elevation above sea level and time zone.

The blue line is the total number of requests, and the red line the total number of credits used. You can ignore the red line and focus on the blue line:

Geonames stats

No surprise that most of you plan or actually perform your photography at the weekends: we always see the highest usage at the weekend and the lowest (typically) in the early part of the week (Monday or Tuesday). That’s why we try to schedule releases of updates early in the week: if anything were to go awry, the fewest users would be affected. (That’s the theory at least!)

We saw a significant usage spike (in fact, our seventh biggest day ever) on the Monday when we released the 2.4 update to TPE for iOS, which added back Google Maps. Clearly a good number of your were interested to try that out. Also, we’d pre-announced the update and the release timing here on the blog, so users knew when to expect it.

Finally, we saw another mid-week spike this week, coinciding with the Full Moon. This is another recurring pattern we see: a monthly spike (more or less) that coincides with the full moon (or the day ahead of full moon).

In fact, all of our top five biggest usage days have be associated with moon events: super moon, especially, and lunar eclipses.

While far from being the only factor, these sort of facts and figures are very useful in giving insight into our core user base and help us prioritize new features and functionality.

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Here in Colorado, November is the month of great sunrises and sunsets. The weather patterns settle down after the summer monsoon season, and standing clouds (often lenticular clouds) persist next to the eastern slopes of the Rocky Mountains.

Colorado Sunset 1

Tonight’s sunset was a perfect example: I’d watched the clouds sit in place all day. Around mid-day there was a reasonable bit of cloud cover over the mountains themselves, but as afternoon progressed, those cleared, leaving only the standing clouds you see in the photo above.

Colorado Sunset 2

While the sunset didn’t quite develop into the glories of this past weekend (which was quite exceptional), it was great to see nonetheless.

With views to the west obstructed only by the mountain peaks of the continental divide, and clear skies beyond, colour can persist long after local sunset. (For more information on the factors involved in determining how long to wait, you can check out our “Waiting for the Light” Infographic.)

The first photo above was taken at 4:44pm today, 9 minutes after local sunset:

You can see the mountains to the west on the map. The grey pin marks the continental divide, along the line of the sun position. Note how the sun continues to travel north after it has set (it’s 2° below the horizon by this time). The lateral movement of the sun during twilight can be significant at moderate latitudes (it’s less pronounced here at 40°N than it is, say, in Scotland at 56 or more degrees north).

A few hours from now will see the smallest full moon of 2012. Not only that, but for some, the full moon will be accompanied by a penumbral eclipse.

Since “supermoon” earlier this year, each subsequent full moon has occurred with the moon farther from Earth. With the November full moon, the moon is very close to “apogee”, the farthest point from earth in the lunar cycle. On TPE for iOS, you can see the difference in time between full moon and apogee is only a few hours (see screenshot above).

The smaller size of the full moon certainly does not prevent you taking successful photographs – yes, it is smaller, but only a little. (Read 5 Useful Numbers for Sun and Moon Photographers if you’d like to know more about the impact on relative size of the moon in your photos.)

The penumbral eclipse is not likely to be a visually dramatic phenomenon (I don’t think I’ve knowingly observed one myself previously), but will likely produce some visible shading of the moon, once it is well underway

You can find out much more about the phenomenon over on NASA’s site.

If you wondered if there is a connection between the penumbral eclipse and the moon being at apogee, you’d be correct. As I understand it, a penumbral eclipse can only occur when the moon is farther from earth – in simple terms, the penumbra of the earth is a smaller target than the umbra proper. From what I’ve read, it appears that penumbral eclipses are actually less common than partial or full eclipses of the moon.

Here in Colorado, the eclipse will be timed with the setting moon, early tomorrow morning. With some luck (and a functioning alarm clock), it may be possible to catch it over the Rockies during early civil twilight.

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If you photograph outdoors, chances are you shoot the sun or the moon. Here are five useful numbers that can help plan your shot to best advantage.

29.5 Days: the Lunar Cycle

The cycle of the moon – from new moon to new moon – lasts 29.5 days on average. Once a month, you have the opportunity to photograph the moon in each of its phases!

The moon is tricky: the average calendar month lasts 30.4 days, so the moon’s 29.5 day cycle means that the lunar cycle moves one day sooner each month. One effect is that on some days the moon either does not rise or does not set. And from time to time – once in a blue moon, in fact – there are four full moons in a season, rather than three.

Different phases of the moon present different photographic opportunities. At full moon, the sun’s rays strike perpendicular to its surface, washing out interesting detail on the moon’s surface. Compare that with the quarter moon, where side lighting allows even a modest telephoto lens to show the topography of the moon to good effect.

The Quarter Moon

Since cameras have a limited dynamic range, it is best to control contrast by shooting at twilight or when the sun is still up, so you can include landscape features or city skylines in your shot.

You can use TPE to see which months have the full moon setting or rising during twilight. The day before full moon is often best to shoot the rising moon in the east around sunset. The day after full moon is often best to catch it setting in the west in the morning around sunrise.

15 Hours: the Youngest New Moon

The instant of new moon cannot be seen with the naked eye: the moon is incredibly thin and lies close to the sun in daylight at this time. The youngest new moon ever sighted by the naked eye was 15 hours 32 minutes old.

The moon has actually been photographed at the precise moment of new moon, using an array of special equipment; it is an amazing achievement, but perhaps not the most visually striking photograph in terms of scenic beauty.

Consequently, the exact time of new moon is of limited value. If you want to photograph the new moon without special equipment, you need to know when it will first become visible. This can be one, two or even three days after the stated new moon time – and it certainly will be a minimum of 15 hours after.

TPE uses a method developed by Dr. Bernard Yallop of Her Majesty’s Nautical Almanac Office to predict when to sight the new crescent moon: plan your shoot around the best time shown by TPE for the first day when the crescent moon becomes visible (over two full days after new moon, in the screenshot below):

Crescent Moon Visibility

14% Larger: Supermoon

The phenomenon of “supermoon” has caught the public’s attention in recent years. It was widely reported that the supermoon of 6 May 2012 was “14% bigger”.

14% bigger than what?

The moon’s journey around Earth is not circular. Through the lunar cycle, the moon moves closer and farther from Earth. Combine that with the elliptical orbit of the Earth around the sun and you have something that doesn’t look as quite neat as the solar system models we all built at school.

Supermoon is the name given to the full moon at perigee. Perigee is the point during the lunar cycle when the moon makes its closest approach to Earth. Apogee is when the moon is most distant from Earth.

Moon at Perigee

The 14% figure is the observed width of the perigee moon compared to the apogee moon. 14% doesn’t sound much, so does it actually matter to photographers?

For telephoto shots, yes.

A 14% increase in diameter corresponds to a 30% increase in area. For example, shooting with a Nikon D300 and a 500mm lens, supermoon will be around 880 by 880 pixels in your shot. An apogee full moon will only cover around 770 by 770 pixels (see diagram below).

0.5°: the Half-Degree Rule

As seen from Earth, the sun and moon both occupy a width of approximately 0.5° in the sky.

The half-degree rule is a rule of thumb: both sun and moon in fact vary in observed size over time. The sun increases from 0.52° at aphelion in June to 0.54° at perihelion in December. The moon varies even more: from 0.48° to 0.56°.

The solar eclipse of May 20 2012 was an Annular eclipse: the moon was further from Earth and did not fully mask the sun, resulting in that striking ring-of-fire appearance.

When photographing the sun or moon the half-degree rule can help with your shot planning. If you know the moon is approximately half a degree in diameter, and want it to occupy a certain fraction of the frame, you can calculate the camera and lens combination you’ll need.

A 35mm full frame camera with a 200mm lens has a field of view of 10° across in landscape orientation. This means that the moon at 0.5° diameter will only occupy 1/20th the width of the frame (0.5° divided by 10°). By extension, if we doubled the focal length of the lens to 400mm the moon will still only occupy 1/10th of the frame.

A camera with a smaller sensor, say a crop factor of x1.6, and a 500mm lens gives a field of view of 3.4°. The moon would then occupy one fifth of the frame – much better!

Perigee vs Apogee

4 Minutes per Degree: Earth’s Rotation

The Earth takes four minutes to rotate by one degree. How do we know this?

1 day = 24 hours = 1440 minutes
1 day = one rotation of the earth = 360°
1440 minutes / 360° = 4 minutes/degree

We can use this information to gain a sense of how quickly the sun or moon will move in the sky. Using the half-degree rule, we can quickly determine that they will take around two minutes to move by one diameter.

This gives a pretty good idea of what is going to happen in those frenzied photographic moments just before sunset or moonset!

Hold your hand at arm’s length and clasp the moon between your thumb and forefinger. That’s half a degree. Now, still with your hand at arm’s length, take that distance and count how many times you can fit it in between the bottom of the moon and the horizon. Is it three times? You’ve got around six minutes left before moonset. You’d better stop reading this and take the photograph!

(Warning: never look directly at the sun. Doing so can cause permanent damage to your eyesight.)

Once you begin to use the size of the sun and moon as a yardstick, it’s easy to develop an instinctive sense of their movement. For outdoor photographers, this is invaluable when estimating how long before the sun will disappear behind a ridge or building without having to pull the smartphone out!

Remember, though: the sun and moon don’t just move vertically. It’s important to account for lateral movement too: for example, the low winter sun skims along the horizon. TPE can help you understand and plan for this.

Knowing how fast the moon is moving in the sky is also useful when planning longer exposures or multiple exposures.

There’s a practical limit to how long a successful exposure of the moon can be. As we know, the body will move by its own width in around 2 minutes. That means a 30 second exposure of the moon will see it smeared across the frame by one quarter its diameter: you need a much faster shutter speed!

When setting up multiple exposure shots of the moon, anything less than two minutes between exposures and the moon will overlap. Four-minute intervals will give a better spacing.


If you’ve enjoyed this post, you might also enjoy “Understanding Light with The Photographer’s Ephemeris” co-authored with renowned landscape photographer Bruce Percy. It’s available through Bruce’s web-site.

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