Gegenschein – The Amazing Sky

April 1, 2019April 1, 2019

Dinosaur Park in the Dark

Winter Sky Setting in Twilight at Dinosaur Park

There’s a slogan used in the U.S. National Parks that “half the Park is after dark.” It is certainly true at Dinosaur Provincial Park in Alberta.

Last Friday night, March 29, I spent the evening at one of my favourite nightscape sites, Dinosaur Provincial Park, about an hour’s drive east of my home. It was one of those magical nights – clear, mild, dry, and no mosquitoes! Yet!

I wanted to shoot Orion and the photogenic winter sky setting into the evening twilight over the Badlands landscape. This was the last moonless weekend to do so.

I shot some individual images (such as above) and also multi-panel panoramas, created by shooting a series of overlapping images at equal spacings, then stitching them later at the computer.

Winter Sky Setting at Dinosaur Park Panorama — This is a 240° panorama stitched from 17 segments, all with the 24mm Sigma Art lens and Nikon D750 in portrait orientation, each segment 20 seconds at f/1.4 and ISO 3200. Stitched with Adobe Camera Raw.

There’s a narrow window of time between twilight and full darkness when the Milky Way shows up well but the western sky still has a lingering blue glow. This window occurs after the normal “blue hour” favoured by photographers.

The panorama above shows the arch of the winter Milky Way but also the towering band of the Zodiacal Light rising out of the twilight and distant yellow glow of Calgary. Zodiacal Light is sunlight scattering off meteoric and cometary dust orbiting in the inner solar system, so this is a phenomenon in space not in our atmosphere. However, the narrow streak is an aircraft contrail.

Spring Sky Panorama at Dinosaur Park — A 360° panorama of the spring sky over the Badlands of Dinosaur Provincial Park, Alberta. This is a panorama of 12 segments taken with the 14mm Sigma Art lens and Nikon D750 in portrait orientation, all for 30 seconds at f/2.8 and ISO 4000. Taken at 30° spacings. Stitched with PTGui.

Later that night, when the sky was fully dark I shot this complete panorama showing not only the Milky Way and Zodiacal Light to the west, but also the faint arc of the Zodiacal Band continuing on from the pyramid-shaped Zodiacal Light over into the east, where it brightens into the subtle glow of Gegenschein. This is caused by sunlight reflecting off interplanetary dust particles in the direction opposite the Sun.

Both the Band and Gegenschein were visible to the naked eye, but only if you knew what to look for, and have a very dark sky.

The Winter Stars and Zodiacal Light at Dinosaur Park — This is a panorama stitched from 3 segments, all with the 24mm Sigma Art lens and Nikon D750, for 20 seconds at f/2.2 and ISO 4000. Stitched with Adobe Camera Raw.

A closeup shows the Zodiacal Light in the west as the subtle blue glow tapering toward the top as it meets the Milky Way.

It takes a dark site to see these subtle glows. Dinosaur Park is not an official Dark Sky Preserve but certainly deserves to be. Now if we could only get Calgary, Brooks and Bassano to turn down and shield their lights!

Spring Sky RIsing at Dinosaur Park Panorama — A 180° panorama of the spring sky and constellations rising in the east over the Badlands of Dinosaur Provincial Park, Alberta on March 29, 2019. This is a stitch of 6 segments, each with the 14mm Sigma Art lens and Nikon D750 in portrait mode, each 30 seconds at f/2.8 and ISO 4000. Stitched with PTGui.

A closeup facing the other way, to the east, shows the area of sky opposite the Milky Way, in the spring sky. The familiar Big Dipper, now high our spring sky, is at top with its handle pointing down to Arcturus and Spica (just rising above the horizon) – remember to “arc to Arcturus, and speed on to Spica.”

Leo is at right of centre, flanked by the Beehive and Coma Berenices star clusters.

Polaris is at left — however, the distortion introduced by the panorama stitching at high altitudes stretches out the sky at the top of the frame, so the Dipper’s Pointer stars do not point in a straight line to Polaris.

The faint Zodiacal Band is visible at right, brightening toward the horizon in the Gegenschein.

I shoot images like these for use as illustrations in future eBook projects about stargazing and the wonders of the night sky. Several are in the works!

Clear skies!

March 19, 2017

The Ghostly Glow of Gegenschein

Northern Spring Sky Panorama

It takes a dark spring night to see it well, but now lurking near Jupiter is a ghostly sky glow called Gegenschein.

This diffuse glow lies directly opposite the Sun. It is caused by sunlight reflecting off interplanetary dust particles in the outer solar system. They reflect light more effectively at the anti-Sun point where each dust particle is fully lit by the Sun.

Like the Sun, the Gegenschein moves around the sky along the ecliptic, moving about a degree from west to east from night to night. March and April provide good nights for seeing the Gegenschein as it then lies in an area of sky far from the Milky Way.

Even so, it is very subtle to the unaided eye. Look south at about 1 a.m. local daylight time.

However, this year, in early April the Gegenschein will be more difficult as it will then lie right on top of Jupiter, as that planet reaches its point opposite the Sun on April 7. Jupiter will then be superimposed on the Gegenschein.

The main image at top is a 7-image vertical panorama of the spring sky, from Corvus and Virgo above the horizon, up past Leo, into Ursa Major and the Big Dipper overhead. Spica lies below bright Jupiter, Arcturus in Böotes is at left, while Regulus in Leo is at right. The grouping of stars near centre is the Coma Berenices star cluster.

Orion over the Old Barn

Earlier in the night, I shot the sky’s other main glow – the Milky Way, as the winter portion of the Milky Way around Orion set into the southwest.

But over in the west, at the right edge of the frame, is the Zodiacal Light, caused by the same dust particles that create the Gegenschein, but that are located in the inner solar system between us and the Sun.

The Zodiacal Light is better depicted in images in my previous post from Dinosaur Park.

We bid adieu to the winter Milky Way now. As it departs we are left with an evening sky without the Milky Way visible at all. As seen from northern latitudes it lies along the horizon.

But later in spring, late at night, we’ll see the summer Milky Way rising, beginning its seasons of prominence until late autumn.

March 14, 2017March 14, 2017

A Starry Night in the Badlands

Winter Milky Way Arch and Zodiacal Light

In a winter of cloud, the skies cleared for a magical night in the Alberta Badlands.

Two weeks ago, on February 28, I took advantage of a rare and pristine night to head to one of my favourite spots in Dinosaur Provincial Park, to shoot nightscapes of the winter sky over the Badlands.

A spate of warm weather had melted most of the snow, so the landscape doesn’t look too wintery. But the stars definitely belong to winter in the Northern Hemisphere.

The main image above shows the winter Milky Way arching across the sky from southeast (at left) to northwest (at right). The tower of light in the west is the Zodiacal Light, caused by sunlight reflecting off dust particles in the inner solar system. It is an interplanetary, not atmospheric, effect.

Winter Sky Panorama at Dinosaur Park (Fish-Eye View) — This is a stitch of 6 segments with the 12mm Rokinon lens at f/2.8 for 30 seconds each, with the Nikon D750 at ISO 6400, mounted portrait. Stitched with PTGui.

Above, this 360° version of the scene records the entire sky, with the winter Milky Way from horizon to horizon. With a little averted imagination you can also trace the Zodiacal Light from west (right) over to the eastern sky (left), where it brightens in the diffuse glow of the Gegenschein, where dust opposite the Sun in the outer solar system reflects light back to us.

Winter Sky Panorama at Dinosaur Park (with Labels) — This is a stitch of 6 segments taken with the 12mm full-fame fish-eye Rokinon lens at f/2.8, all 30-second exposures with the Nikon D750 at ISO 6400. The camera was aimed portrait with the segments at 60° spacings. Stitched with PTGui using equirectangular projection with the zeith pulled down slightly.

A rectangular version of the panorama wraps the sky around from east (left), with Leo rising, to northeast (right), with the Big Dipper standing on its handle. I’ve added the labels in Photoshop of course.

Winter Stars over Dinosaur Park — This is a stack of 8 x 30-second exposures for the ground, mean combined to smooth noise, plus one 30-second exposure for the sky. All at f/2.2 with the Sigma 20mm Art lens and Nikon D750 at ISO 6400.

Here, in a single-frame shot, Orion is at centre, Canis Major (with Sirius) is below left, and Taurus (with Aldebaran) is at upper right. The Milky Way runs down to the south. The clusters M35, M41, M46 and M47 are visible as diffuse spots, as is the Orion Nebula, M42, below Orion’s Belt.

Evening Zodiacal Light at Dinosaur Park — The late winter evening Zodiacal Light, from at Dinosaur Provincial Park, Alberta, February 28, 2017. This is a stack of 7 x 30-second exposures for the ground, mean combined for lower noise, plus one 30-second exposure for the sky, all at f/2 with the 20mm Sigma Art lens, and Nikon D750 at ISO 6400.

This is certainly my best shot of the evening Zodiacal Light from my area in Alberta. It is obvious at this time of year on moonless nights, but requires a site with little urban skyglow to the west.

It is best visible in the evening from northern latitudes in late winter and spring.

Here, Venus is just setting above the badlands landscape. The Andromeda Galaxy is at right, the Pleiades at left. The Milky Way runs across the frame at top.

There is a common belief among nightscape photographers that the Milky Way can be seen only in summer. Not so.

What they mean is that the brightest part of the Milky Way, the galactic centre, is best seen in summer. But the Milky Way can be seen in all seasons, with the exception of spring when it is largely absent from the early evening sky, but rises late at night.

February 29, 2016

A Panorama of the Spring and Winter Sky

Winter and Spring Sky Panorama

I present a sweeping panorama of the winter and spring stars on a February night.

The lead image is a panorama I shot last Saturday, February 27 that takes in about 200° of sky from northeast to west, and nearly to the zenith. It encompasses most of the northern spring and winter stars and constellations.

I’ve added the labels to help you pick out the celestial highlights. The winter sky, containing Orion as the central constellation, is at right setting into the west. This area of sky contains a rich collection of bright stars and identifiable constellations.

The left side of the sky contains the spring constellations, now coming into view in the east. Note how that area of sky is sparsely populated by bright stars. You can see the Big Dipper, Regulus in Leo, and Arcturus rising at lower left.

The reason for the difference is the Milky Way – you can see it at right arcing up from the southern horizon passing by Orion and through Gemini, Taurus and Auriga. In that direction we are looking into the outlying spirals arms of our galaxy, toward rich areas of star formation.

To the east, at left, we are looking at right angles out of the plane of our spiral galaxy, toward the galactic North Pole, here just left of Leo. In that direction there are very few bright stars between us and the starless depths of intergalactic space. The spring sky is rather blank compared to the rich winter sky.

But you can see Jupiter, the brightest object in view here, and now prominent in the evening sky.

Note one other subtle glow just above Jupiter. That diffuse glow is the Gegenschein, caused by sunlight reflecting off interplanetary dust opposite the Sun in our solar system and in the plane of the ecliptic.

Jupiter is just east (left) of the Gegenschein here, as Jupiter was then just over a week before its date of opposition, March 8. By then the Gegenschein will have moved to superimpose right over Jupiter, as both then lie opposite the Sun.

Winter and Spring Sky Panorama

I shot this scene from home on February 27, 2016, using the new iOptron iPano motorized “gigapan” unit, which I programmed to move and shoot 36 exposures with the Canon 5D MkII and 35mm lens, arranged in 4 rows high with 9 panels wide in each row from east to west. The result is a huge mosaic, 24,000 by 10,000 pixels.

Each exposure was 25 seconds at f/2 and at ISO 3200. The camera was not tracking the sky. I stitched the 36 segments with PTGui using its Spherical Fisheye projection. The image has black margins but I think the circular format is more suggestive of the spherical dome of the sky above and around you. But that’s me, a longtime planetarium show producer.

Next time I will shoot the zenith cap images as well!

December 11, 2015December 14, 2015

The Wonder-Filled Winter Sky

Mosaic of the Wonder-filled Winter Milky Way

The sky of December contains an amazing array of bright stars and deep-sky delights.

At this time of year we peer out toward the edge of our Galaxy, in the direction opposite to what we see in July and August. Even though we are looking away from the centre of our Galaxy, the Milky Way at this time of year contains a stunning collection of sights – for the naked eye, binoculars or a telescope.

I can’t list them all here, but most are in the lead image above! The image is a mosaic of the northern winter Milky Way, including the brilliant stars and constellations in and around Orion the Hunter.

The Milky Way extends from Perseus in the north at top, to Canis Major in the south at bottom. Throughout the scene are dark lanes and dust clouds, such as the Taurus Dark Clouds at upper right.

The Milky Way is dotted with numerous red “hydrogen-alpha” regions of emission nebulosity, such as the bright Rosette Nebula at lower left and the California Nebula at upper right. The curving arc of Barnard’s Loop surrounds the east side of Orion. Orion is below centre, with Sirius, the night sky’s brightest star, at lower left.

The constellation of Taurus is at upper right and Gemini at upper left. Auriga is at top and Perseus at upper right.

There’s an unusually bright area in Taurus just right of centre in the mosaic which I thought might be an image processing artifact. No. It’s the Gegenschein – a glow of sunlight reflected off comet dust directly opposite the Sun.

Two highlights of this sky that are great regions for binoculars are the Hyades cluster in Taurus ….

The Hyades Cluster with Aldebaran — The Hyades open star cluster in Taurus with the bright star Aldebaran, not a part of the cluster iteslf. The smaller and more distant cluster NGC 1647 is at left. This is a telephoto lens image taking in a field similar to binoculars, and is a stack of 5 x 2.5-minute exposures with the 135mm lens at f/2 and Canon 5D MkII camera at ISO 800, plus two other exposures taken through the Kenko Softon filter to add the star glows. Taken from Quailway Cottage on Dec 7, 2015 using the iOptron Sky-Tracker.

…and the Belt and Sword of Orion.

The Hyades – the face of Taurus – is one of the nearest and therefore largest open star clusters.

Orion the Hunter, who battles Taurus in the sky, contains the famous Orion Nebula, here overexposed in order to bring out the much fainter nebulosity in the region.

The magenta and blue arcs in the image below are photographic targets, but the bright Orion Nebula in Orion’s Sword is easy in binoculars, shining below the trio of his Belt Stars.

Orion Belt and Sword Mosaic — A mosaic of the Sword and Belt region of Orion the Hunter, showing the diverse array of colourful nebulas in the area, including: curving Barnard’s Loop, the Horsehead Nebula below the left star of the Belt, Alnitak, and the Orion Nebula itself as the bright region in the Sword. Also in the field are numerous faint blue reflection nebulas. The reflection nebula M78 is at top embedded in a dark nebula, and the pinkish NGC 2024 or Flame Nebula is above Alnitak. The bright orange-red star at far right is W Orionis, a type M4 long-period variable star. This is a 4-panel mosaic with each panel made of 5 x 2.5-minute exposures with the 135mm Canon L-series telephoto wide open at f/2 and the filter-modified Canon 5D MkII at ISO 1250. The night was somewhat hazy which added natural glows on the stars. No filter was employed here. The camera was on the iOptron Sky-Tracker for tracking but no guiding. Shot from outside Quailway Cottage near Portal, Arizona, Dec 7, 2015. All stacking and stitching performed in Photoshop CC 2015. Stacking done with median combine stack mode to eliminate geosat trails through the fields.

For us in the northern hemisphere, Orion and company are winter sights. But for those down under, in the southern hemisphere, this is the summer sky. So pardon the northern chauvinism in the title!

Either way, on a dark, moonless night, get out and explore the sky around Orion.

TECHNICAL:

I shot the segments for the main mosaic at top on a very clear night on December 5, 2015 from the Quailway Cottage at Portal, Arizona. This is a mosaic of 8 segments, in two columns of 4 rows, with generous overlap. Each segment was made of 4 x 2.5-minute exposures stacked with mean combine stack mode to reduce noise, plus 2 x 2.5-minute exposures taken through the Kenko Softon filter layered in with Lighten belnd mode to add the star glows. Each segment was shot at f/2.8 with the original 35mm Canon L-series lens and the filter-modified (by Hutech) Canon 5D MkII at ISO 1600, riding on the iOptron Sky-Tracker. All stacking and stitching in Photoshop CC 2015. The soft diffusion filter helps bring out the star colors in this area of sky rich in brilliant giant stars.

March 15, 2015

The Ghostly Glows of a Truly Dark Sky

A truly dark sky isn’t dark. It is filled with glows both subtle and spectacular.

Last night, March 10, I drove up into the heart of the Gila Wilderness in southern New Mexico, to a viewpoint at 7,900 feet in altitude. I was in search of the darkest skies in the area. I found them! There was not a light in sight.

The featured image is a 180° panorama showing:

– the Zodiacal Light (at right in the west)
– the Milky Way (up from the centre, in the south, to the upper right)
– the Zodiacal Band (faintly visible running from right to left across the frame at top)
– the Gegenschein (a brightening of the Zodiacal Band at left of frame, in the east in Leo)

The Zodiacal Light, Zodiacal Band, and the Gegenschein are all part of the same phenomenon, glows along the ecliptic path – the plane of the solar system – caused by sunlight reflecting off cometary and meteoric dust in the inner solar system.

The Gegenschein, or “counterglow,” can be seen with the naked eye as a large and diffuse brightening of the sky at the spot exactly opposite the Sun. It is caused by sunlight reflecting directly back from comet dust, the scattering effect greatest at the point opposite the Sun.

The Zodiacal Light requires reasonably dark skies to see, but the fainter Zodiacal Band and Gegenschein require very dark skies.

Now is prime season for all of them, with the Moon out of the way, and the Zodiacal Light angled up high in the western as twilight ends. In March, the Gegenschein is now located in a relatively blank area of sky in southern Leo.

The Milky Way is much more obvious. Along the northern winter Milky Way here you can see dark lanes of interstellar dust, particularly in Taurus above and to the right of Orion. Red nebulas of glowing gas also lie along the Milky Way, such as Barnard’s Loop around Orion.

– Orion is at centre, in the south, with Canis Major and the bright star Sirius below and to the left of Orion. Canopus is just setting on the southern horizon at centre. It barely clears the horizon from 32° North latitude.

– To the right of Orion is Taurus and the Pleiades star cluster at the top of the Zodiacal Light pyramid.

– Venus is the bright object in the Zodiacal Light at right, in the west, while fainter Mars is below Venus.

– At far right, in the northwest, is the Andromeda Galaxy, M31.

– Jupiter is the bright object at upper left, in the east, in the Zodiacal Band, and near the Beehive star cluster.

– The Zodiacal Light, Band and Gegenschein all lie along the ecliptic, as do Mars, Venus and Jupiter.

Glows on the horizon are from distant SIlver City, Las Cruces and El Paso. The brighter sky at right is from the last vestiges of evening twilight. Some green and red airglow bands also permeate the sky.

I shot this March 10, 2015 from the summit of Highway 15, The Trail of the Mountain Spirits, that twists and winds through the Gila Wilderness.

It was a stunning night, clear, calm, and silent. Just me under the ghostly glows of a truly dark sky.

NOTE: I first published this March 11 but had to republish this blog March 15 after WordPress deleted the original post in a software bug. Thanks WordPress!

April 1, 2014

Observing under the Southern Stars

The Milky Way arches over our observing field at the OzSky star party in Australia.

What an amazing few nights it has been. We’ve enjoyed several clear nights under the fabulous southern Milky Way. About 40 people from around the world have had access to telescopes from 14-inch to 30-inch aperture to explore the wonders of the southern sky from a dark site near Coonabarabran, New South Wales.

I’ve seen lifetime-best views of the Tarantula Nebula, the Carina Nebula, the Horsehead Nebula, the Omega Centauri cluster, and on and on! But the views of Mars have been incredible, the best I’ve seen the planet in a decade as it is now close to Earth and high in our southern sky.

The panorama above is a stitch of 6 untracked segments taken with a Canon 60Da and 8mm fish-eye lens. Each segment is a 60-second exposure at ISO 3200.

The 360° panorama takes in the Milky Way from Canis Major setting at right, over to Scorpius and Sagittarius and the centre of the Galaxy rising at left. At top centre is the wonderful Carina and Crux area. The two Magellanic Clouds are just above the trees at centre.

At upper left is Mars, and just to the left of it is a diffuse glow – the Gegenschein, sunlight reflected of comet dust in the direction opposite the Sun. Mars is near that point now. You can just see a faint band running from the Gegenschein to the Milky Way — the Zodiacal Band of comet dust.

Here, one of our observers takes in a view through a 24-inch reflector telescope under the stars of the Southern Cross, the pattern in the Milky Way behind him.

The nights have been warm and wonderful, though a little damp and dewy after midnight. However, rain is in the forecast again, a welcome relief for most local residents who want the rain. They can have it now. We’re happy!

March 20, 2013

The Ghostly Glow of Gegenschein

The band of light at right is the familiar Milky Way. But what’s that faint stream of light to the left? It’s called the Gegenschein.

My last blog showed an image of the Zodiacal Light in the west. In fact, that glow extends up and continues all the way across the sky as a very faint stream of light at the threshold of vision called the Zodiacal Band. But at the place in the sky 180° opposite the Sun the Band intensifies to become a diffuse patch of light. It’s easy to see with the naked eye from a dark site if you know to look for it, and where it is likely to be. Last week, it was sitting below the constellation of Leo, in an area of sky that is pretty blank. So any faint glow stands out.

As with Zodiacal Light, what you are seeing is sunlight reflected off comet and asteroidal dust, but for the Gegenschein (German for “counterglow”) the light is coming from dust opposite the Sun that is scattering light back toward us and the Sun, mirror-like. The back-scattering effect makes the dust appear a little brighter at the point opposite the Sun.

Spring is a good time to spot the Gegenschein (true for the northern or southern hemisphere) as it then lies in a sparse area of sky away from the Milky Way. But you need a moonless sky and a dark site free of manmade light pollution. It and the fainter Zodiacal Band are among the sky’s most subtle sights. Again, Atmospheric Optics has more details.

A bonus with this shot are some short streaks of light below and to the right of the Gegenschein. I think those are from geostationary satellites flaring at the anti-solar point as they, too, acted as mirrors briefly catching the sunlight. Being geostationary – likely communications satellites you aimed fixed dishes at – they stayed still while the stars and tracking camera moved, and so created streaks.

February 8, 2013February 9, 2013

A Crisp Winter’s Night Under the Stars

It was crisp and frosty night filled with the bright stars of winter, and the Milky Way.

This was the sky from my backyard on Thursday, February 7, with Orion and his friends shining due south. It is a “fish-eye” shot taking in all of the sky from horizon to horizon. South is at bottom, north to the top. West is at right, east to the left.

The Milky Way runs from northwest, at top right, to southeast, at bottom left. When we look at this section of the Milky Way we are looking in the direction opposite the galactic core, toward the outer arms of our Galaxy.

Jupiter is the brightest “star” in the image, shining in Taurus. Rising out of the sky glow from towns to the west of me is the pillar of light called the Zodiacal Light. I think you can follow it stretching all the way across the sky from right to left (west to east) where it then becomes a subtle bright patch in the sky well east of the Milky Way. That’s the Gegenschein, a glow of light exactly opposite the Sun. It and the Zodiacal Light are caused by sunlight reflecting off comet dust in the inner solar system.

A night when you can see the Zodiacal Light and Gegenschein – they were visible to the unaided eye – is a good night indeed. Too bad this one was spoiled by some cloud and haze, reflecting the toxic yellow glow of ever-intruding sodium vapour lights.

Silhouetted in the sky glow at right is one of my telescopes, with camera #2 dutifully taking a closeup image of Orion’s Belt. That picture will be the subject of tomorrow’s blog!