Arc of the Low Summer Moon


Arc of the Summer MoonThe summer Full Moon arcs low across the southern sky, mimicking the path of the winter Sun.

This is a project I had in mind for the last month, and hoped to capture at the July Full Moon. A clear, dry, and cooperative night provide the chance.

The still images are composites of 40 images of the Moon traveling across the sky from dusk to dawn, taken at 10-minute intervals. They are layered onto a blend of background images of the 10 p.m. dusk sky (left), 2 a.m. middle-of-the-night sky (middle), and 5 a.m dawn sky (right).

As a bonus, the 10 p.m. sky shows some dark crepuscular rays in the twilight, while at 2 a.m. the Moon was in light cloud and surrounded by iridescent colours. By 5 a.m. denser clouds were moving in to obscure the Moon.

Arc of the Summer Moon

I shot the still image composite (above) and time-lapse movie (below) to illustrate the low arc of a summer Full Moon. In summer (June or July) the Full Moon sits at a similar place near the ecliptic as does the Sun in winter near the December solstice.

From the northern hemisphere the low position of the winter Sun gives us the short, cold days of winter. In summer, the similar low position of the Full Moon simply gives us a low Full Moon! But it is one that can be impressive and photogenic.

The time-lapse movie uses all 400 frames of the moving Moon superimposed onto the same background sky images, but now dissolving from one to the other.

 

The movie is 4K in resolution, though can be viewed at a smaller resolution to speed up playback if needed.


For the technically minded:

The Moon disks in the time-lapse and still composite come from a series of short 1/15-second exposures, short enough to record just the disks of the bright Moon set against a dark, underexposed sky.

I took these shots every minute, for 400 in total. They are blended into the bright background sky images using a Lighten blend mode, both in Photoshop for the still image, and in Final Cut for the movie.

The background sky images are longer exposures to record the sky colours, and stars (in the case of the 2 a.m. image). They are blended with gradient masks for the still image, but dissolved from one to the other in the time-lapse movie.

I shot the frames with a 15mm full-frame fish-eye lens and Canon 6D, with the camera not moved during the 7-hour shoot.

— Alan, July 12, 2017 / © 2017 Alan Dyer / amazingsky.com 

The Moving Stars of the Northern Hemisphere


Arizona Star Trails - Circumpolar Looking North

I present a montage of time-lapses illustrating the motion of the sky in the Northern Hemisphere. 

Any stargazer should be familiar with how the sky moves, with stars rising in the east and setting in the west.

From the northern hemisphere, when we look north we see the sky rotating counter-clockwise around the North Celestial Pole, near Polaris. As you’ll see in the video, even Polaris moves, though not much over the night. The stars that never set, but just move across the northern horizon, are the circumpolar stars.

When we look south we see the seasonal constellations, the ones that rise and set, and change over the seasons.

I shot the images for these sequences from southern Arizona, in early December 2015.

So the night starts with the summer stars setting in the west and the autumn stars dominating the sky. But then Orion and the winter stars rise and march across the sky over the night, setting before dawn, as the spring stars rise.

The south-looking movie is a dusk-to-dawn sequence. Note the Zodiacal Light in the west at right in the early evening, then reappearing in the east at left before dawn brightens the sky, and as Venus and the Moon rises.

Also note the moving bands of red and green airglow, a natural phenomenon of the upper atmosphere.

 

I posted a matching set of movies in my previous blog post, shot from the Southern Hemisphere. But here’s the link to the movie.

 

Both sets of movies were shot from nearly identical latitudes – about 31°, but 31° N for Portal, Arizona and 31° S for Coonabarabran, Australia.

As such the Celestial Poles appear at equal altitudes above the horizon. And the angles that the stars rise and set at in relation to the horizon are the same.

But the direction they move is opposite. When looking 180° away from the Pole, the seasonal stars move from left to right in the Northern Hemisphere, but from right to left in the Southern Hemisphere.

Visitors from one hemisphere to the other are bound to get turned around!

— Alan, August 25, 2016 / © 2016 Alan Dyer / AmazingSky.com

 

The Moving Stars of the Southern Hemisphere


Southern Sky Star Trails - OzSky Looking South

Nothing amazes even the most inveterate skywatcher more than traveling to another hemisphere and seeing sky move. It moves the wrong way!

Whether you are from the southern hemisphere traveling north, or as I do, travel south from the Northern Hemisphere, watching how the sky moves can be disorienting.

Here I present a video montage of time-lapses shot last April in Australia, at the annual OzSky Star Party near Coonabarabran in New South Wales.

Select HD and Enlarge button to view at full screen at best quality.

You’ll see the sky set in the west but traveling in arcs from right to left, then in the next clip, rise in the east, again moving from right to left. That’s the wrong angle for us northerners.

Looking north you see the seasonal constellations, the ones that rise and set over a night and that change with the seasons. In this case, the night starts with Orion (upside-down!) to the north but setting over in the west, followed by Leo and bright Jupiter. The sky is moving from east to west, but that’s from right to left here. The austral Sun does the same thing by day.

Looking south, we see the circumpolar constellations, the ones that circle the South Celestial Pole. Only there’s no bright “South Star” to mark the pole.

The sky, including the two Magellanic Clouds (satellite galaxies to the Milky Way) and the spectacular Milky Way itself, turns around the blank pole, moving clockwise – the opposite direction to what we see up north.

I shot the sequences over four nights in early April, as several dozen stargazers from around the world revelled under the southern stars, using an array of impressive telescopes supplied by the Three Rivers Foundation, Australia, for us to explore the southern sky.

I’ll be back next year!

– Alan, August 19, 2016 / © 2016 Alan Dyer / www.amazingsky.com

 

Time-Lapse Techniques — Creating Star Trails


Dinosaur Park Star Trails (May 26, 2013)

The stars wheel above the Cretaceous-age sediments of Dinosaur Provincial Park.

One of the most powerful techniques in the nightscape photographer’s arsenal is to stack lots of short-exposure images together to create the equivalent of one long exposure showing the motion of the stars. A creative tool to do this in Photoshop is the “Advanced Stacking Actions” from Steven Christenson who maintains a blog and eStore called Star Circle Academy.

I used one of his Actions to create the feature image above. Unlike more run-of-the-mill stacking procedures, Christenson’s nifty Actions can create star trails that look like comets or streaks fading off into the sky at their tail end. It’s a clever bit of Photoshop work achieved by stacking each successive image at slightly lower opacity.

You can use his Actions to create a single composite still image, as above, or to create a set of “intermediate” frames that can be turned into a time-lapse movie with stars turning across the sky and drawing trails behind them. My movie shows several variations. Click the Expand button on the movie to have it fill the screen and reveal the sub-titles.

In Clip #1 I stacked the original set of 360 images without any trailing, using the original frames that came from the camera, albeit with each frame processed to enhance contrast and colour.

In Clip #2 I stacked the images using the “Comet Trails” Action, one that produces very short comet-like streaks.

In Clip #3 I used the “Long Streak” Action to produce longer star trails, but the process also creates unusual cloud streaks as well. Rather neat.

In Clip #4 I used the more conventional “Lighten Mode” to create trails that accumulate over the entire sequence and never fade out. The result on this night was pretty wild and excessive, with the twilight and moonlight adding other-worldly colours.

I certainly recommend the Star Circle Academy Photoshop Actions. While there is a basic Test Set available for free, the full Advanced set is well worth the $30.

– Alan, June 1, 2013 / © 2013 Alan Dyer