All-Night Satellites


ISS Pass #2 (June 4-5, 2013)

It was a marvellous night for Space Station watching.

Right now those of us at northern latitudes in North America are enjoying the opportunity to see the International Space Station come over not once but often 2 or 3 times a night, as it is now lit by the Sun all night long (on our nights down here on Earth, that is).

Here are two shots from the night of June 4-5, 2013 taken from my home in Alberta at a latitude of 51° North.

My featured image above is from the ISS pass that began at 1:55 am, and is a stack of 4 tracked 2.5-minute exposures, so the stars are not trailed, but the ground is! On this pass, the ISS came overhead. This view is looking north, toward the all-night perpetual twilight we see on the Canadian Prairies around summer solstice. There’s also a low band of green aurora on the northern horizon.

I shot the image below on the ISS’s pass one orbit earlier at 12:18 am. This image is looking south to the ISS’s high pass across the south. It’s a composite of 4 untracked 2-minute exposures –  thus the stars are now trailing in circles around Polaris at the top of the frame.

ISS Pass #1 (June 4-5, 2013)

Both shots are horizon-to-horizon all-sky views with an 8mm fish-eye lens.

The sky isn’t dark, even in the shot taken at 2 am. At this time of year around summer solstice at northern latitudes, the sky never gets astronomically dark but is lit a deep blue by sunlight still streaming over the pole and bathing the night in a glow of perpetual twilight.

– Alan, June 5, 2013 / © 2013 Alan Dyer

 

The Clouds Keep Coming!


Clouds aren’t usually the astronomer’s friend, but at this time of year they become the objects of our attention. For the past few nights, my Alberta prairie skies have been beautifully clear and filled with the clouds of solstice.

Last night, July 6, began at twilight with the best display of noctilucent clouds so far this season — and we’re now at peak season for this northern sky phenomenon. This was the scene at about 11:30 pm local time, with the wispy high-altitude clouds at their most extensive and fully lit by sunlight. Over the next hour or so, as the Sun set further below the horizon, the display disappeared as darkness came to the high atmosphere and the Sun no longer illuminated these clouds suspended over the Arctic. Here’s a diagram of the geometry of how they get lit up. If you are curious to learn more, check this NASA page.

I took a time-lapse movie of the fall of darkness on the clouds, which you can view here at my SmugMug gallery at AmazingSky.ca. The video shows how the clouds begin the night fully illuminated by the Sun but over the hour duration of the video they disappear from top to bottom. You can see a curtain of darkness moving down the clouds, caused by the Sun dropping farther below the horizon. As it does so its illumination seems to drop toward the horizon as night falls, leaving only clouds closest to the horizon (and farthest north) still illuminated. The video also shows that the edge of the illumination appears reddish — that’s because clouds on the edge of the descending dark shadow are being lit only by a low red Sun setting below the limb of the Earth. Pretty neat, and something I’ve not seen before in any image or movie. (The movie is HD quality and will take a while to load, sorry!)

However, tonight normal, everyday weather clouds moves in, curtailing any late night NLC watch. Tomorrow, I head to the Rockies to do some time-lapse nightscape shooting in the mountains. Yes, I know I’ll miss seeing Duke and Duchess Will and Kate start off the Calgary Stampede Parade. Royalty will just have to get on without me.

— Alan, July 7, 2011 / Image © 2011 Alan Dyer

Arctic Ice-Blue Clouds at Dawn


We were treated to a good display of noctilucent clouds last night. Or should I say early this morning! At this time of year, many a night is spent keeping a watchful vigil for noctilucent clouds. They often appear at their best before dawn.

That was the case July 5/6. The night started with a decent display of these northern sky clouds in the northwest after sunset and just before midnight. But then as the Sun dropped lower below the horizon, the lighting angles changed and the clouds disappeared. A low aurora display took their place through most of the night.

Then, at 3 am or so, as the lighting from the rising Sun hit the right angle coming over the Pole, the Arctic ice clouds reappeared, now in the northeast. Sequences of shots showed a rapid east to west motion of the clouds, driven by winds at the edge of space, at the clouds’ extreme altitude of 80 km or so.

This shot is with a 16-35mm zoom, set to 24mm and takes in the bright star Capella at upper right, a useful “survey marker” for measuring angles and cloud altitudes. I took this at about 3:30 am. MDT.

— Alan, July 6, 2011 / Image © 2011 Alan Dyer

The Glowing Clouds of Solstice Appear


The glowing clouds of solstice have appeared. This was my first sighting of “noctilucent clouds” for the season.

Every northern summer in late June and early July we are often treated to bright pearly clouds glowing along the northern horizon long after sunset. Their origin remains somewhat of a mystery. These clouds form almost at the edge of space, so high there shouldn’t be much for clouds to form around. But their height is what makes them visible, as they catch sunlight streaming over the pole even in the middle of the night.

I took this shot Tuesday, June 28 just before midnight. The noctilucent clouds are the blue-white wavy bands just above the orange twilight. In front of them lie dark normal clouds low in our troposphere. But the NLCs shine from an altitude of some 80 km, well into the mesosphere. They are located over the Northwest Territories but, like aurora, their height allows us to see them even from more southerly latitudes.

The bright star Capella, circumpolar from my latitude of 51° North, shines through the clouds at right.

— Alan, June 28, 2011 / Image © 2011 Alan Dyer

Summer Solstice Space Station, Part 2


Here’s a capture of the Space Station, coming over in a darker, clearer sky than last night’s shot (in the previous blog). This was June 22, 2011, a fine solstice night on the Canadian Prairies.

The time was just before midnight, with no Moon. Yet the sky is blue and the northern horizon tinged with the orange glow of twilight. It never gets truly dark now, as summer begins. To the right, on the northeast horizon, a low green aurora kicks up.

The Space Station, the dashed arc at top, tonight passed from west to southeast, across the southern sky at the top of this fisheye 360° frame.

This is a stack of 28 18-second exposures at f/4 and ISO 1600 with the Canon 5D MkII and Sigma 8mm lens.

— Alan, June 22, 2011 / Image © 2011 Alan Dyer

 

 

Summer Solstice Space Station


We’re currently enjoying a series of nightly (and often twice or thrice nightly) passes of the International Space Station, coinciding with the bright nights of summer solstice.
I took this shot on the night of solstice, June 21, 2011, as the Space Station came directly overhead, flying out of the west then heading off into the east. So we’re looking a little west of north here, toward the bright northern horizon. Pity some light cloud hazed up the sky. The pass began at 11:12 pm so the sky was still quite bright, though even an hour or two later at this time of year the northern horizon is tinged with perpetual twilight glow, at least at my latitude of 51° N.
To create the image I took a series of 100 3-second exposures (as long as the bright sky would allow) taken 1 second apart in rapid-fire fashion with the camera firing automatically with a remote timer. The 1 second gap between exposures creates the gaps in the Space Station trail.
I processed the images in Adobe Camera Raw, and exported them all as TIFFs to their own folder. I then used Chris Schur’s excellent “Star Trails” Photoshop Action to stack all those images into one composite image showing the complete flight of the Space Station across the sky. A little application of Shadows and Highlights helped bring out the foreground and bright sky detail.
I used the Sigma 8mm fisheye lens and Canon 5D Mk II to capture the whole sky, for a still and time-lapse sequence suitable for projection in a full-dome video planetarium … because the neat thing about this method is that the same set of images can be strung together sequentially (using Photoshop Extended’s Movie function) into a time-lapse movie of the pass, showing cloud and star motion as well as the ISS passage. The same techniques work for star trails, as indeed you can see here with the stars of the northern sky (Big Dipper at left and Cassiopeia at right) trailing around the North Star.
— Alan, June 22, 2011 / Image © 2011 Alan Dyer