October 2011 – The Amazing Sky

October 16, 2011October 17, 2011

Calgary Lights Up

I’m getting the hang of shooting demanding day-to-night time-lapse movies!

For this clip I shot over 2.5 hours, using a fish-eye lens, to create a sequence suitable for projection in a digital planetarium dome.

But the trick with these day-to-night sequences is getting a smooth transition in exposures, which can range over 12 to 16 f-stops, from short snapshot exposures with the lens stopped all the way down at the start before sunset, to long 8-second exposures with the lens wide open at night, plus the camera’s ISO speed increasing from a slow ISO 100 to a faster ISO 400 or more at select points through the sequence as well.

The secret to doing this is a control box called the Little Bramper, an intervalometer that fires the shutter automatically at set intervals but also gradually ramps the exposure time a tad longer with each successive exposure. This was my third time out with the Bramper, and I more or less got it right this time!

While the Bramper does a great job running the camera, it still takes a lot of manual oversight to control its ramping rate so the exposures don’t get too long and overexpose the scene, or fail to get long enough to track the darkening sky.

At several points in the sequence it is also necessary to quickly (in one exposure cycle) half the exposure time, while at the same time opening up the lens a stop, or doubling the ISO, so that the ever-lengthening exposure doesn’t get too long and collide with the interval between exposures. In this case, shots were taken about 12 seconds apart, so the maximum exposure for each frame couldn’t be much more than 8 to 10 seconds.

The end result of the work is a time-lapse movie that shows the setting Sun, then the lights of Calgary coming on as the sky darkens. Clouds lit by the yellow glow of streetlights move in, then blow away again to reveal a few stars in the urban sky.

October 10, 2011

Little Church on the Prairie

In honour of Canadian Thanksgiving, here’s a shot from last night of a classic little church on the Canadian Prairie.

This is the long abandoned Catholic church at the hamlet of Dorothy, Alberta. The church was built in 1944, but as the coal mines in the Drumheller valley shut down (blame the invention of Diesel trains and the discovery of natural gas in Alberta) the once bustling town of Dorothy decayed into a ghost town. A few people still live there, but its main attractions are its relics of the pioneer age — this church, and the United church next to it (behind the camera), a picturesque grain elevator, and an old store. The companion United church has been restored, but this little church on the prairie, abandoned since 1967, awaits restoration.

The scene is lit by the gibbous Moon, and by a couple of sodium vapour streetlights, ubiquitous even in a ghost town.

In the sky are the stars of the Big Dipper and Polaris above the church.

This is one frame of 300 I shot over three hours as part of a motion-controlled time-lapse movie.

Happy Thanksgiving!

October 7, 2011

Set the Controls for Triangulum

Spiral galaxies are icons of deep space. This one is a classic. This is the Triangulum Galaxy, named for its home constellation. Amateur astronomers also know it as M33, the 33rd entry in Charles Messier’s catalog of deep sky objects compiled in the 1780s. To Messier, object #33 was another fuzzy spot he and others might confuse for comets, the objects astronomers of the day were really after.

It wasn’t until 1850 that the Earl of Rosse, observing with his monster Leviathan of Parsonstown, a 72-inch reflector telescope, managed to see M33 as something more than a nebulous glow. He saw what the photo clearly shows — spiral arms swirling around a central core. However, in those days, such “spiral nebulae” were thought to be whirlpools of gas where stars and solar systems were forming.

It wasn’t until the 1920s, with the work of Edwin Hubble, that objects like M33 were proven to be other galaxies like our Milky Way, each composed of billions of stars.

We now know the Triangulum Galaxy lies about 3 million light years away, and is about half the size of our Milky Way. That makes it the third largest member of our Local Group of galaxies, after our own Milky Way and the famous Andromeda Galaxy.

For this shot of M33, taken September 25, I stacked 6 images, each a 12-minute exposure at ISO 800 and f/6, shot with my Astro-Physics 130mm refractor and Canon 7D camera. Visible along the galaxy’s spiral arms you can see some of the reddish and cyan-coloured nebulas that are sites of active star formation in M33.

October 1, 2011June 1, 2014

Milky Way Mosaic

It’s taken me a few months to get around to the task, but at last! — my mosaic of the Milky Way I shot in Chile back in May.

The panorama is made up of 6 frames, stitched and blended together, extending from Crux, the Southern Cross (at right) to Aquila the eagle (at left) — a sweep of the Milky Way from Acrux to Altair! The mosaic is centred on the core of the Galaxy in Sagittarius and Scorpius.

Panoramas like this allow you to step back a distance and take in the big picture:

— You can see the large-scale structure of the dust clouds and the odd diagonal sweep of many of the clouds cutting across the plane of the Galaxy. I’ve never heard an explanation of why the dust lanes seem to have that structure and direction. I also see a 3D effect, with the nearby dust clouds hanging in front of and obscuring the bright starclouds of the distant inner spirals arms of our Galaxy.

— Also apparent are the extensive dust clouds at left extending from Ophiuchus (at top) down into Aquila, well below the plane of the Galaxy. Most wide-angle shots of the Milky Way I see tend to process out the subtle brown clouds that extend far off the Galactic plane. And they are brown, not black.

— And what really stands out is the band of bright blue stars from Scorpius (at top centre) to the right above the Milky Way through Lupus, Centaurus then down into Crux. This is a section of Gould’s Belt, a ring of hot blue stars around the sky that runs at an angle of about 20° to the Milky Way. This ring of hot, nearby stars surrounds us in our spiral arm and is thought to be only about 65 million years old, likely caused by some disturbance in our spiral arm which set off a wave of star formation close to us.

— And … as my Australian friends will point out, you can see the entire Dark Emu, made of the dust lanes from the Coal Sack in Crux at right (his head and beak), through the curving lanes in Centaurus (his neck), then sweeping up and over the centre of the Galaxy (his body) then down into Scutum and Aquila (his two feet and his tail).

I took this panorama from the Atacama Lodge in north central Chile, using the Canon 5D MkII and Canon 35mm lens. Each of the 6 segments that went into this pan was itself a stack of 4 x 6 minute exposures, plus a fifth exposure through a soft-focus filter, all at f/4 and ISO 800. The camera was on a Kenko SkyMemo tracking platform. I assembled the pan with Photoshop CS5’s Photomerge command. This is actually only half of the full panorama mosaic, which extends for another 5 segments to the right along the Milky Way to Orion, taking in the entire southern portion of the Milky Way. But this is the best bit!

October 1, 2011

Legends of the Fall

These stars are as much a part of autumn in the northern hemisphere as are the changing colours of leaves and the flying south of geese.

These are the stars of legend, outlining the mythical constellations of Queen Cassiopeia (at top left), her daughter Andromeda (arcing across the bottom half of the image), and the hero Perseus (the stars at lower left) who rescued Andromeda from the ravages of Cetus the sea monster.

These stars are now high in the east in the evening sky, heralding the start of autumn and the return of frosty nights.

There are lots to see with binoculars or a telescope in these constellations. Look around this image and you can pick out several clumps, or clusters, of stars in Perseus and Andromeda. But the most obvious object is the oval-shaped Andromeda Galaxy, visible to the unaided eye from dark rural skies. This is the nearest sizeable galaxy to our Milky Way, and yet its light still takes 2.5 million years to reach us.

I took this shot earlier this week during a run of clear and warm autumn nights, perhaps the last before the chill nights of fall come on. It’s a wide-angle shot with a 35mm lens and Canon 5D MkII camera, tracked for a stack of four 6-minute exposures plus a fifth taken with a soft-focus filter.