Tracks of the Geosats

This short video, below, captures time-lapses of the trails of geostationary satellites through southern Orion. It demonstrates the “crowded sky” we now have above us. 

If you have tried photographing the Orion Nebula and Sword of Orion area with long tracked exposures you have no doubt seen these trails in your photos. Here I shot to purposely capture them in a time-lapse, for demonstration purposes. 

Please note, these are not Starlink satellites. So do not blame Elon Musk for these! 

These are the much more established geostationary or “geosynchronous” satellites that orbit 35,785 kilometres above Earth and so take 24 hours to orbit the planet. As such they remain apparently motionless over the same spot on Earth, allowing fixed dish antennas to aim at them.

(For more about geosats see the Wikipedia page.)

So why are they moving here?

The camera is on a mount that is tracking the sky as it turns from east to west, so the stars are staying still. What would normally be satellites fixed in one spot in the sky (after all, they are called “geostationary” for a reason) instead trail into short streaks traveling from west to east (right to left) in the frame. But in reality, it is the stars that are in motion behind the satellites. 

The region of sky in Orion below the Orion Nebula (the object at top) lies south of the line that bisects the sky into northern and southern halves called the “celestial equator.” Most geostationary satellites also orbit in Earth’s equatorial plane and so appear along a belt near the celestial equator in the sky. 

This chart from SkySafari shows the belt of geosats through southern Orion with the satellites identified. The green box is the field of view of the telescope (shown below) that I used to take the time-lapses.

In this video, however, they appear about 5° to 7° south of the celestial equator (which runs through the famous Belt of Orion off frame at top). That’s because I live north of the equator of the Earth, at a latitude of 51° north. So parallax makes the geosat belt appears south of the celestial equator in my sky. From a site in the southern hemisphere the geosat belt would appear north of the celestial equator.

You’ll notice some satellites travelling diagonally — they are not geosats. You’ll also see some flashing or pulsing satellites — they are likely tumbling objects, perhaps spent rocket boosters.

The satellites are visible because they are high enough to reflect sunlight even in the middle of the night, as the sequences each end about 11:30 to midnight local time.

But in this video the satellites are not flaring — this is their normal brightness. During flare season around the two equinoxes geosats can become bright enough to be seen with the unaided eye. For a video of that phenomenon see my video shot in October 2020, below. 


The video at top contains time-lapses shot on two nights: January 18 and 20, 2021. Both are made from hundreds of frames taken through a William Optics RedCat astrograph at f/5 with a 250mm focal length. The field of view is 8° by 5.5°. 

The William Optics RedCat 51mm f/5 astrographic refactor.

Each exposure is 30 seconds long, taken at a one second interval. The camera was a Canon 6D MkII at ISO 3200 on January 18 and ISO 1600 on January 20 in the brighter moonlight that night. 

In the first sequence from January 18 the equatorial mount, an Astro-Physics Mach1, is left to track on its own and is unguided. So the stars wobble back and forth slightly due to periodic error in the mount. The field also drifts north due to slight misalignment on the pole. Clouds pass through the field during the shoot. 

In the second clip from January 20, taken with a quarter Moon lighting the sky, the mount was autoguided, using an MGEN3 auto-guider. So the stars remained better fixed over the 5.5 hours of shooting. A slight glitch appears near the end where I swapped camera batteries, and the camera turned ever so slightly causing the stars to enlarge a bit for a moment. 

LRTimelapse at work processing the second sequence, deflickering some of the oddly exposed frames.

The frames were processed in Adobe Camera Raw and LRTimelapse

TimeLapse DeFlicker at work assembling the video, showing its All Frames + Lighten blend mode for the Accumulating version of clip #2.

I then assembled exported JPGs with TimeLapseDeFlicker, using a 3-frame Lighten blend mode to lengthen the trails. The final version was assembled with TLDF’s All Frames mode (shown above) where every frame gets stacked for an accumulated total, to show the busy sky traffic! 


— Alan, © 2021 / 

Lilac Passages of the ISS

ISS Title Page

I present a short video, in 4K, of two video clips of the International Space Station in two successive passages across the sky on May 24/25, 2018.

The location was my backyard in southern Alberta.

The clips were shot in 4K in real-time video at 24 frames per second but with a 1/4-second shutter speed with a Sony a7III camera, and with 15mm full-frame fish-eye (first clip) and 8mm circular fish-eye lenses. ISO speeds were 6400 and 16,000.

The clips are sped up by 2x and 4X in post-production to make a shorter video for the web. The background sounds of the night are real-time and were recorded live with the videos.

What I cannot capture is the smell!

The lilacs were in bloom and lent a wonderful fragrant scent to the night air, which added to the sights and sounds of a spring night.

Thus the title of the video.

Much of North America is now enjoying great passes of the ISS. To find out when you can see it from your backyard see NASA’s Spot the Station website and enter your location.

– Alan, May 26, 2018 / © 2018 Alan Dyer /


Conjunctions, Satellites & Auroras, Oh My!

Friday the 13th Aurora Title

October has brought clear skies and some fine celestial sights. Here’s a potpourri of what was up from home. 

We’ve enjoyed some lovely early autumn weather here in southern Alberta, providing great opportunities to see and shoot a series of astronomical events.


Venus & Mars in Close Conjunction #2 (Oct 5, 2017)
Venus and Mars in close conjunction in the dawn sky on October 5, 2017. Venus is the brightest object; Mars is below it; while the star above Venus is 4th magnitude Sigma Leonis. The foreground is illuminated by light from the setting Full Moon in the west. This is a single 1-second exposure with the 135mm lens at f/2 and Canon 60Da at ISO 800. 

On October 5, Venus and Mars appeared a fraction of a degree apart in the dawn twilight. Venus is the brightest object, just above dimmer but red Mars. This was one of the closest planet conjunctions of 2017. Mars will appear much brighter in July and August 2018 when it makes its closest approach to Earth since 2003.

Satellites: The Space Station

Overhead Pass of the Space Station in Moonlight
An overhead pass of the ISS on October 5, 2017, with the Full Moon rising in the east at left. The ISS is moving from west (at right) to east (at left), passing nearly overhead at the zenith at centre. North is at the top, south at bottom in this fish-eye lens image with an 8mm Sigma fish-eye lens on the Canon 6D MkII camera. This is a stack of 56 exposures, each 4 seconds long at an interval of 1 second. 

The Space Station made a series of ideal evening passes in early October, flying right overhead from my site at latitude 51° N. I captured it in a series of stacked still images, so it appears as a dashed line across the sky. In reality it looks like a very bright star, outshining any other natural star. Here, it appears to fly toward the rising Moon.

Satellites: Iridiums

Twin Iridium Satellite Flares (October 9, 2017)
A pair of nearly simultaneous and parallel Iridium satellite flares, on October 9, 2017, as they descended into the north. The left or westerly flare was much brighter and with a sharp rise and fall in brightness. While it was predicted to be mag. -4.4 I think it got much brighter, perhaps mag -7, but very briefly. These are Iridium 90 (left) and Iridium 50 (right). This is a stack of 40+ exposures each, 2 seconds at 1-second intervals, with the Sigma 24mm lens at f/1.4 and Nikon D750 at ISO 6400.

Often appearing brighter than even the ISS, Iridium satellite flares can blaze brighter than even Venus at its best. One did so here, above, in another time-lapse of a pair of Iridium satellites that traveled in parallel and flared at almost the same time. But the orientation of the reflective antennas that create these flares must have been better on the left Iridium as it really shot up in brilliance for a few seconds.


Aurora and Circumpolar Star Trails (Oct, 13, 2017)
A circumpolar star trail composite with Northern Lights, on October 13, 2017, shot from home in southern Alberta. The Big Dipper is at bottom centre; Polaris is at top centre at the axis of the rotation. The bottom edge of the curtains are rimmed with a pink fringe from nitrogen. This is a stack of 200 frames taken mostly when the aurora was a quiescent arc across the north before the substorm hit. An additional single exposure is layered in taken about 1 minute after the main star trail set to add the final end point stars after a gap in the trails. Stacking was with the Advanced Stacker Plus actions using the Ultrastreaks mode to add the direction of motion from the tapering trails. Each frame is 3 seconds at f/2 and ISO 6400 wth the Sigma 14mm lens and Nikon D750.

Little in the sky beats a fine aurora display and we’ve had several of late, despite the Sun being spotless and nearing a low ebb in its activity. The above shot is a composite stack of 200 images, showing the stars circling the celestial pole above the main auroral arc, and taken on Friday the 13th.

Aurora from October 13, 2013
A decent aurora across the north from home in southern Alberta, on Friday the 13th, October, 2017, though these frames were taken after midnight MDT. 3 seconds at f/2 and ISO 6400 wth the Sigma 14mm lens and Nikon D750.

This frame, from some 1300 I shot this night, October 13, captures the main auroral arc and a diffuse patch of green above that pulsed on and off.

You can see the time-lapse here in my short music video on Vimeo.

Friday the 13th Aurora from Alan Dyer on Vimeo.

It’s in 4K if your monitor and computer are capable. It nicely shows the development of the aurora this night, from a quiescent arc, through a brief sub-storm outburst, then into pulsing and flickering patches. Enjoy!

What all these scenes have in common is that they were all shot from home, in my backyard. It is wonderful to live in a rural area and to be able to step outside and see these sites easily by just looking up!

— Alan, October 16, 2017 / © 2017 Alan Dyer / 


Night of the Space Station

A pass of the International Space Station in the bright moonlight, on the evening of May 31, 2015, with the gibbous Moon to the south at centre. The view is looking south, with the ISS travelling from right (west) to left (east) over several minutes. This was the first pass of a 4-pass night, May 31/June 1, starting at 11:06 pm MDT this evening. Numerous other fainter satellite trails are also visible. This is a composite stack of 95 exposures, each 2 seconds at f/2.8 with the 14mm lens and ISO 6400 with the Canon 6D. The gaps are from the 1-second interval between exposures. The length of the trails and gaps reflects the changing apparent speed of the ISS as it approaches, passes closest, then flies away.  I stacked the exposures with the Advanced Stacker Actions from, using the Lighten mode. The ground comes from a Mean blend of just 8 of the exposures to prevent shadows from blurring but to smooth noise.

The Space Station is now continuously lit by sunlight, allowing me to capture dusk-to-dawn passages of the ISS.

On the night of May 31/June 1 I was able to shoot four passages of the International Space Station on successive orbits, at 90-minute intervals, from dusk to dawn.

The first passage, at 11:06 p.m., was low across the south. It’s the image at top.

An overhead pass of the International Space Station in a bright moonlit sky on the night of May 31/ June 1, 2015, with the gibbous Moon in to the south, below. The view is looking south, with the ISS travelling from right (west) to left (east) over several minutes. This was the second pass of a 4-pass night, May 31/June 1, starting at 12:44 am MDT this morning.  This is a composite stack of 91 exposures, each 4 seconds at f/3.5 with the 8mm fish-eye lens and ISO 6400 with the Canon 6D. The gaps are from the 1-second interval between exposures. The length of the trails and gaps reflects the changing apparent speed of the ISS as it approaches, passes closest, then flies away. The stars are trailing around Polaris at top. An aircraft supplies the other dashed trail across the top and intersecting with the ISS trail. I stacked the exposures with the Advanced Stacker Actions from, using the Lighten mode. The ground comes from a Mean blend of just 8 of the exposures to prevent shadows from blurring but to smooth noise.

Then at 12:45 a.m. the Space Station came over again, now directly overhead. It’s the image above. The Moon is the bright glow at bottom.

An overhead pass of the International Space Station in a bright moonlit sky on the night of May 31/ June 1, 2015, with the gibbous Moon in the southwest, below. The view is looking south, with the ISS travelling from right (west) to left (east) over several minutes. This was the third pass of a 4-pass night, May 31/June 1, starting at 2:21 am MDT this morning.  This is a composite stack of 66 exposures, each 4 seconds at f/3.5 with the 8mm fish-eye lens and ISO 6400 with the Canon 6D. The gaps are from the 1-second interval between exposures. The length of the trails and gaps reflects the changing apparent speed of the ISS as it approaches, passes closest, then flies away. The stars are trailing around Polaris at top. Unfortunately, I missed catching the start of this pass. I stacked the exposures with the Advanced Stacker Actions from, using the Lighten mode. The ground comes from a Mean blend of just 8 of the exposures to prevent shadows from blurring but to smooth noise.

One orbit later, at 2:21 a.m., the Station came over in another overhead pass in the bright moonlight.

A pass of the International Space Station in the brightening twilight of dawn, on the morning of June 1, 2015, with the gibbous Moon setting to the southwest at right. The view is looking south, with the ISS travelling from right (west) to left (southeast) over several minutes. This was the last pass of a 4-pass night, May 31/June 1, starting at 3:55 am MDT this morning.  This is a composite stack of 144 exposures, each 2 seconds at f/2.8 with the 15mm full-frame fish-eye and ISO 3200 with the Canon 6D. The gaps are from the 1-second interval between exposures. The length of the trails and gaps reflects the changing apparent speed of the ISS as it approaches, passes closest, then flies away.  I stacked the exposures with the Advanced Stacker Actions from, using the Lighten mode. The ground comes from a Mean blend of just 8 of the exposures to prevent shadows from blurring but to smooth noise.

The final passage of the night came at 3:55 a.m. as the sky was brightening with dawn twilight and the Moon was setting. This was another passage across the south, and made for the most photogenic pass of the night.

Here’s an edited movie of the four passes, with a little music just for fun.

Seeing the Space Station on not one but two, three, or even four orbits in one night is possible at my latitude of 50 degrees north around summer solstice because the Station is now continuously lit by sunlight — the Sun never sets from the altitude of the ISS.

When the ISS should be entering night, sunlight streaming over the north pole still lights the Station at its altitude of 400 km.

To shoot the time-lapse clips and stills I used 8mm and 15mm fish-eye lenses, and a 14mm ultra-wide lens.

The bright moonlight made it possible to use short 2- to 4-second exposures, allowing me to record enough frames at each passage to make the little movies of the ISS flying across the sky. Keep in mind, to the eye, the ISS looks like a bright star. Some image processing trickery adds the tapering trails.

I used the Advanced Stacker Actions from to create the trail effects, and to stack the time-lapse frames into single composite still images. The gaps in the trails are from the one second interval between frames.

– Alan, June 2, 2015 / © 2015 Alan Dyer /

What Was That Glow in the Sky?

Here’s a time-lapse of the strange glow of light that moved across the northern sky on the night of the Camelopardalid meteor shower.

What I thought was an odd curtain of slow-moving, colourless aurora — and I’ve seen those before — has many people who also saw it suspecting it was a glow from a fuel dump from an orbiting satellite. Perhaps.

This short time-lapse of 22 frames covers about 22 minutes starting at 11:59 pm MDT on May 23 (as logged by the camera’s GPS). Each frame is a 60-second exposure taken at 2 second intervals. I’m playing them back at one frame per second.

The camera was on a tracking platform to follow the stars — thus the ground slowly rotates. This was one of the cameras I had operating the night of May 23-24 to capture meteors from the Camelopardalid meteor shower. The shower was a dud, but …

The most interesting thing my cameras did catch was this odd glow which started large and diffuse and then became more defined as it got smaller and moved off (or so it appears) to the north, then fades away. My photos (and I have it on frames from another camera), and photos taken by other observers across North America, show a faint satellite moving along south to north parallel to the cloud’s long axis. Is this the culprit that caused the cloud? If so, it would have to be very high to be seen from a wide range of longitudes – astronomers in Manitoba and Minnesota also saw and shot it.

But any fuel dumps I’ve seen always have clouds that start small and concentrated then become large and diffuse. This did the opposite.

I’ll await further analysis and explanation.

P.S.: You can watch a better version of the movie here at my Flickr site.

— Alan, May 25, 2014 / © 2014 Alan Dyer




Big Dipper Over Castle Mountain

Big Dipper over Castle Mountain, Banff (Aug 24, 2013)

The famous stars of the Big Dipper dip behind the moonlit crags of Castle Mountain.

I just got back from four days in Banff, always a great place to be, even if it is cloudy. And it was!

I lost one night to forest fire smoke and another to rain clouds. On Saturday and Sunday nights I managed to seek out some clearer skies for nighttime shooting. This is a shot from Saturday, from a favourite photo stop on the Bow Valley Parkway overlooking the cliffs of Castle Mountain.

Despite the dew from rains earlier in the day I managed to shoot a time-lapse here. These two shots are frames from the movie which pans slowly across the scene.

Iridium Flare over Castle Mountain

This frame catches an Iridium satellite flare above the Dipper.

Light from the waning gibbous Moon, which was in and out of clouds itself, illuminates the scene and nicely cross-lights the Castle cliffs.

– Alan, August 26, 2013 / © 2013 Alan Dyer


Space Station Over a Star Party

ISS Pass Over Star Party (August 10, 2013)

The Space Station flies over a campground of astronomers awaiting the fall of darkness.

Last night was the main night for summer star parties, being a dark-of-the-Moon Saturday in August. As I usually am each year, I was in Cypress Hills, Saskatchewan, attending the annual Saskatchewan Summer Star Party. About 330 attended this year, a near record year.

The night was partly cloudy but stayed clear enough for long enough to allow great views. As the sky was getting dark the International Space Station flew over from horizon to horizon, west to east, passing nearly overhead. I had a camera and ultra-wide lens ready and caught the pass in 10 exposures, each 30 seconds long, here stacked in Photoshop. The accumulated exposure time also makes the stars trail in circles around the North Star at upper right.

It was one of many fine sky sights hundreds of stargazers enjoyed this weekend at the SSSP, and no doubt at dozens of other star parties around the continent this weekend.

– Alan, August 11, 2013 / © 2013 Alan Dyer

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


Commander Chris Flies Over My House

ISS Pass with Chris Hadfield (April 17, 2013)

Commander Chris Hadfield and his crew fly over my house and below the Moon on a spring night in Canada.

It’s been a couple of months since we in Canada have had a chance to sight the Space Station in our evening sky with our Canadian astronaut on board. When I last had a chance in February, Chris was a crew member. Now he’s the commander of the Station, the first Canadian to hold the position.

My shot, taken tonight on the second of two passes this evening, has the Space Station coming up out of the west and rising to meet the Moon. It passed under the Moon and then faded out as it entered Earth’s shadow and nighttime, one of 16 nights they experienced this and every day in orbit around the Earth.

Chris is in orbit with the Expedition 35 crew until mid-May. So this may be our best and last chance to see our astronaut flying through Canadian skies.

This was also the first decently clear night we’ve had in two weeks, since my last post from April 2. We all hope spring is finally  arriving

– Alan, April 17, 2013 / © 2013 Alan Dyer


Flying Through a Moonlit Winter Night

ISS Pass with Astronaut Chris Hadfield (Feb 15, 2013)

Tonight the Space Station flew out of the west and overhead as it faded into the shadow of the Earth.

Because tonight the ISS was coming up high into the north, almost directly overhead, I used a fish-eye lens to shoot the entire sky, and took three exposures, each 90 seconds with the camera tracking the stars.

The bright Moon is at right, but despite its light the Milky Way still shows up. The Space Station faded into sunset just as it crossed the Milky Way.

Canadian astronaut Chris Hadfield is on board, about to take command at the next crew change. He’s been tweeting lots of comments and photos from space. Check him out at @Cmdr_Hadfield.

– Alan, February 15, 2013 / © 2013 Alan Dyer


Space Station Over the Rockies

This was the view Friday night, August 19, 2011, as the International Space Station flew over Banff, Alberta and the Canadian Rockies.

I took this shot (actually this is a composite of three successive exposures) from the viewpoint on Mt. Norquay overlooking the Banff townsite and the Trans-Canada Highway interchange, unfortunately all too well lit. This might well be a case study in light pollution as well.

But the lights in the valley don’t diminish the Milky Way above, and the sky-wide streak created by the passage from west to east of the Space Station. What looks like a brilliant star to the eye turns into a streak here due to the three 45-second time exposures I used to capture this scene. The lens is the 8mm fish-eye, and these frames are from a 400-frame time-lapse movie for the planetarium dome.

— Alan, August 20, 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

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

Goodbye Discovery!

What an awesome spacecraft it has been — launching the Hubble Space Telescope, Ulysses and John Glenn! It returned NASA to manned spaceflight following both the Challenger and Columbia accidents. And now this week, we say goodbye to Space Shuttle Discovery. On Sunday night, Feb. 27, I took a look at it (perhaps my last), and the ISS, as they flew over together in an ideal pass across our sky. Even in binoculars you could see the shape of the ISS — or at least that it had a shape and was not just a star, as all other satellites appear. A great sight was watching the craft fly into Earth’s shadow and go deep red then fade out. That’s why the bright streak the ISS/Shuttle left on the frame during the time exposure fades out at left, as they fly to the east and experience sunset.

To the west (right) note the Zodiacal Light glow reaching up from the western horizon. Orion and Canis Major are at bottom in the south. To the northwest is my house. I purposely left the porch light on around the other side of the house to light up the yard and the photogenic old house on the property. It features in many of my backyard shots.

This shot is a two-image stack of 4-minute exposures, with the Canon 5D MkII at ISO 800 tracking the sky on an equatorial mount. The lens is one of my favourites, the Sigma 8mm full-circle fish-eye lens. Some haze in the sky knocked back the contrast, so the Milky Way doesn’t pop out as well as it should. Still, this was the first clear night in a while when it wasn’t -25°C!

– Alan, February 27, 2011 / Image © 2011 Alan Dyer

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