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



Belt of Venus and Volcanoes

This was the scene we were treated to each evening at the Atacama Lodge in Chile. Quite an amazing skyline, with 5,900-metre-high Licancabur Volcano, here at sunset.

The sky colour comes from a phenomenon known as the Belt of Venus, a magenta/pinkish glow from sunlight lighting up the upper atmosphere after the Sun has set for us on the ground. The dark blue rimming the horizon is the rising shadow of the Earth.

I have punched up the colour saturation here to bring out the colours, but not so much as to be faked — the colours are real!

This is a shot with the 50mm lens and Canon 7D camera, taken on one of the nights we had dinner back at the lodge, in this case with a group of Québec amateur astronomers also here this week who were great observing friends on the field.

– Alan, May 7, 2011 / Image © 2011 Alan Dyer

Easter Sunday Space Station

What a picture perfect pass this was, on Easter Sunday evening, April 24, 2011. The International Space Station (ISS) rose out of the west right on time, passed almost directly overhead, the flew off to the east, fading out just as it approached the horizon. The sky was a deep blue in the late twilight, with the spring stars beginning to appear. As it usually does, the Space Station outshone them all, including Arcturus, the brightest streak at right. The Station also passed just north of the handle of the Big Dipper at the top of the frame.

I took this with the 15mm lens that takes in a field of view from the horizon to almost straight up.

Because the sky was still bright, one long exposure wouldn’t work with this shot. The Station took nearly 3 minutes to traverse the frame. The only way to avoid overexposing the sky would have been to stop the lens way down or use a very slow ISO speed, either of which would have meant the Station and stars might not have recorded very well, especially the fast-moving Station.

So instead, I used what turned out to be thirteen short 15-second exposures at f/4 and ISO 400, taken 1 second apart. Each one is exposed correctly, and the aperture and ISO speed are fast enough to pick up stars and the moving satellite. The trick is to then stack the images in Photoshop. To do this I import the images first from the memory card using Adobe Bridge, then process them in Adobe Camera Raw. ACR provides most of the processing necessary for shots like these – sharpening, noise reduction, some contrast boost, and the usual Vibrance and Clarity. Once processed, I use Bridge’s “Import into Photoshop Layers” command to automatically create a single image with all the processed frames stacked on top of each other in layers. Then it’s a matter of turning the Blend mode of each layer from Normal to Lighten, and voila! – the frames turn transparent and appear merged together, all properly exposed. The result is a single exposure effectively 3 minutes long, long enough that the stars also trail.

In this shot, the 1-second interval between exposures creates the gaps in the ISS trail. I could do a little Photoshop trickery to eliminate those but I think they give a sense of the speed of the ISS as it flies overhead quite quickly when it is closest, then slows down in apparent motion as it flies away into the distance.

A great help in planning a shot like this is Starry Night software – it loads in the latest satellite orbit data and shows the exact path of the satellite across your local sky. So I was ready and waiting with the camera all framed up, knowing just where it would appear, then started the camera firing as the ISS came overhead and into the field of the camera. It was a fine sight on an Easter Sunday.

– Alan, April 2011 / Image © 2011 Alan Dyer