Milky Way Mosaic


Centre of the Milky Way Panorama (2011)

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!

— Alan, Oct 2, 2011 / Image © 2011 Alan Dyer

Centaurus, Creator of Constellations


In George Lucas mythology, Luke Skywalker went to Yoda to learn the wisdom and ways of heroes. In Greek mythology, heroes the likes of  Achilles, Jason and Hercules sought out Chiron, the wise and kindly Centaur, who taught them science, astronomy, medicine, music, arts, hunting and archery.

Centaurs, the romping half man/half horse creatures, were a riotous and drunken lot, but not immortal Chiron. He was the offspring of Kronos and the ocean nymph Philyra and served as tutors to many legendary heroes. One reference in my library suggests Chiron actually invented the constellations, to make it easier for mankind to keep track of the stars and the season. To reward his work, Zeus placed Chiron in the stars, becoming by some accounts, this southern sky constellation, Centaurus.

However, most writings suggest Chiron is actually the Zodiac constellation of Sagittarius, while the constellation we call Centaurus is one of the wilder bunch, depicted in the sky as carrying the slain Lupus the wolf, drawn here in the fainter blue stars at top centre.

The bright stars at right are the main stars of Centaurus, including Alpha and Beta Centauri at lower right. Beta Centauri is the blue star, a giant some 390 light years away. But just to the left of Beta is yellow-white Alpha Centauri, a Sun-like star (or actually a pair of them orbiting each other) just 4.3 light years away.

Alpha and Beta Centauri sit at the start of a long dark rift in the Milky Way that splits into fingers of nebulosity reaching into Norma, Ara and Scorpius, here at the left edge of the frame.

I took this shot of Centaurus and Lupus in Chile last month, using a 50mm lens and a Canon 5D MkII. It’s a stack of four 6-minute exposures at f/4 and ISO 800, layered in with two exposures shot through a Kenko Softon-A filter to produce the photogenic star glows.

— Alan, June 26, 2011 / Image © 2011 Alan Dyer

 

 

 

 

 

Into the Heart of the Scorpion


Here we peer into the heart of Scorpius, to a place where the sky is painted with pastel hues unlike anywhere else in the heavens.

The yellow star at bottom is Antares, the cool supergiant star that marks the heart of the Scorpion. To the right is Messier 4, a globular cluster of thousands of stars. Wrapping the entire field are shrouds of dust, reflecting the yellow light of Antares and the blue light of hotter stars above, such as Rho Ophiuchi at top right. Glowing hydrogen gas clouds add the magenta hues.

The remarkable feature of this field are the dark fingers, clouds of dark interstellar stardust glowing with a dim yellowy-brown hue. In places the clouds become more opaque and intense, blocking any light from background stars. Those clouds must be close by in our galactic spiral arm because few stars lie between us and their dark masses. Estimates put them about 400 light years away.

The entire region is a busy factory of star making, one of the closest to our Sun. Chances are our solar system formed in a similar star factory 5 billion years ago, one that has long since dissolved away and dispersed around the Galaxy.

Like the previous shot, this is a Canon 7D/135mm telephoto image in a stack of six 2-minute exposures, taken from Chile in early May. I find it remarkable that with digital cameras just 2-minute exposures not only bring out the dark nebulas, but actually show them with colour and tonality. In the old days, film shots 20 minutes long only ever showed them as a mass of underexposed and featureless black.

— Alan, June 16, 2011 / Image © 2011 Alan Dyer

Off the Stinger Stars of Scorpius


Off the tail of Scorpius lies one of the great starry regions of the Milky Way. From southern Canada the Scorpion’s Tail barely clears our horizon at this time of year, on June nights. But from farther south, Scorpius crawls high into the sky — and the sky actually gets dark at solstice, so stargazers can see the starclouds of Scorpius in all their glory.

At right, the blue stars mark the “stinger” at the end of the Scorpion’s tail. The brightest one, called Shaula, or Lambda Scorpii, is a hot blue giant star some 10,000 times more luminous than our own modest Sun. It is also a triple star, with another luminous blue star orbiting it, plus a third odd mystery star thought to be either a neutron star or perhaps a young proto-object still in the process of forming a proper “main-sequence” normal star.

To the left lie two prominent clusters of stars: at top the Butterfly Cluster (a.k.a. Messier 6), a bright group of stars sitting amid a dark bay of dust. Below it, almost lost in the stars, is Ptolemy’s Cluster (a.k.a. Messier 7), that is an obvious sight to the unaided eye – so obvious the Greek astronomer Ptolemy catalogued it in 130 AD. Several other star clusters pepper the field.

This telephoto lens shot frames the field as binoculars would show it. I took this from Chile in early May, using the Canon 7D and 135mm lens, for a stack of six 2-minute exposures at f/2.8 and ISO 1250.

— Alan, June 16, 2011 / Image © 2011 Alan Dyer

 

 

The Seven Sisters of the South


Down in the south sit many austral equivalents to namesake northern sky objects: the Southern Cross, the Southern Beehive, the Southern Pinwheel. This is the “Southern Pleiades,” a match to the famous Pleiades star cluster prominent in our northern hemisphere sky. Since our Pleiades also carries the moniker the “Seven Sisters,” I suppose that makes this object the “Seven Sisters of the South.”

The field here again duplicates what binoculars would show, and this is a lovely object for binos. Its resemblance to the northern Pleiades comes from this star cluster’s bright but scattered appearance, and the blue colour of its sorority of stars. Like its northern counterpart, the Southern Pleiades is a cluster of hot young stars which shine furiously blue in their energetic youth. This group is perhaps no more than 50 million years old, and like the northern Sisters, shines quite close by, just 480 light years away, putting it a stone’s throw away down our own galactic spiral arm.

Officially catalogued as IC 2602, and also dubbed the Theta Carinae Cluster, this clutch of blue stars shines just below the Carina Nebula (you can see both together in my earlier blog The Best Nebula in the Sky). A couple of other fainter star clusters also populate the field.

I took this shot with the Canon 7D and 135mm telephoto lens and stacked five 2-minute exposures. Stacking helps smooth out background noise, though in a wide field shot like this, the sheer number of stars tends to overwhelm any camera noise.

— Alan, June 4, 2011 / Image © 2011 Alan Dyer

 

 

 

An Island in a Sea of Stars


This image looks toward the inner spiral arm of our Milky Way called the Norma Arm, where stars bunch together to form the rich Norma Starcloud, a prominent patch in the southern Milky Way. What you see here is all stars, lots and lots of stars.

Seemingly embedded in the sea of stars is an island of brighter stars called the Norma star cluster, or more prosaically NGC 6067. It’s about 6800 light years away, much closer to us than the more distant stars behind it. It is literally floating in front of the background sea of stars.

As with the previous image, this is a wide field shot, taken with the 135mm telephoto, to frame the field much as it would appear in binoculars. This shot is a stack of six 2-minute unguided exposures at ISO 1250 with the Canon 7D riding on the little Kenko tracking platform. It’s one of a couple of dozen fields I shot the first night of shooting on Chile in May.

— Alan, June 4, 2011 / Image © 2011 Alan Dyer

 

 

 

 

Rose of the Southern Sky


It’s been a month since my last post, a month with no new astrophotos from home. But I’ve got a backlog of RAW files to work through from the Chile trip a month ago. Here’s a new image from that shooting expedition. It’s of an area of the southern sky that lends itself to every focal length and framing variation — you can’t go wrong with the Carina Nebula!

This wonderful nebula in the deep-south Milky Way rewards any astrophotographer. For this shot I used a 135mm telephoto (Canon’s wonderful f/2 L-series lens) and the Canon 7D camera. The 7D is what I call a “stock” camera, used just as it comes off the dealer shelf. The 7D does a superb job capturing the red nebulosity and its faint outlying bits and pieces. It tends to record these clouds of glowing hydrogen as magenta in tone. By comparison, my other Canon camera is a “filter-modified” 5D MkII. You can see a shot of this same area of sky taken with the 5D MkII a few blogs back under The Best Nebula in the Sky, posted May 6. The 5D MkII’s modification (which replaces the filter in front of the sensor with a new astro-friendly one) allows it to record deep-red wavelengths and picks up more faint nebulosity, registering it more as red in tone. But both images look good and presentable.

This field is rich in objects — not only the main sprawling nebula but nearby star clusters and patches of dark dust clouds. It is one of the finest fields in the sky for binoculars, and this shot approximates the field of view of typical binos. I like to shoot a lot of objects with telephoto lenses — while the main subject is not frame-filling and in your face, it does match (at least in field of view) what you can see in binos, useful for illustrations and observing articles. Of course, the camera picks up  more stuff and colours even your bino-aided eyes can’t see.

This shot is a stack of five 2-minute exposures at f/2.8 with the 135mm telephoto, on the Canon 7D at ISO 1250. I used the little Kenko Sky Memo tracking platform for this, letting it track without any added guiding. It’s tracking was spot on, with nary any star trailing as it followed the target for 20 minutes or so.

— Alan, June 3, 2011 / Image © 2011 Alan Dyer